Editorial – Uvodnik
Looking Forward to the 45th International
Symposium FORMEC 2012
Dear readers,
I have the honor and pleasure to inform you that
the 45th International Symposium FORMEC 2012 will
be held in Dubrovnik/Cavtat in hotel Croatia from
October 8 to 12 2012 under the title »Concern, Knowledge and Accountability in Today’s Environment«.
»FORestry MEChanization« (known under the
acronym FORMEC since 1994) is an international
scientific network established to investigate and promote the application of mechanization in forest operations and it gathers scientists and experts from
Europe and other countries, who, within forestry,
deal with wood harvesting, forest accessibility and
mechanization of forest operations.
forest accessibility and mechanization of forest operations. Following this idea, the Organizational Committee proposed these topics:
Þ Harvesting systems and technologies,
Þ Forest road network planning and management,
Þ Eco-efficient technologies in forestry,
Þ Biomass production and use,
Þ Logistics and transport optimization,
Þ Forestry and wood industry on close-to-nature
principles,
Þ Work design and business management in forestry,
Þ Ergonomics and work safety in forest operations,
Þ IT and remote sensing in forestry,
Þ Sustainable forest management and silviculture.
Organizers and main objectives
of the Symposium
It was also very important to define the key dates
of the Symposium in order to leave enough time to
the Organizational Committee to perform well and
on time all their tasks (prepare the list of the submitted, accepted or rejected papers, define the schedule
of oral or poster presentations, prepare digital proceedings, etc.), and on the other hand to give to the
authors (Symposium participants) the schedule of
all dates and deadlines associated with them directly
or indirectly. Key dates of the Symposium are as
follows:
Þ Abstract submission deadline: Feb. 29, 2012
Þ Acceptance of abstracts to be made by the Scientific Committee: March 15, 2012
Þ Early registration deadline: May 31, 2012
Þ Full paper submission: July 31, 2012
Þ Registration deadline: Sept. 20, 2012
The main organizers of the 45th International
Symposium FORMEC 2012 are the Faculty of Forestry of the University of Zagreb and FORMEC network, while the co-organizers are yet to be defined
and until the publishing of this editorial, the agreement has been made with IUFRO (International Union
of Forest Research Organizations), Croatian Chamber of Forestry and Wood Technology Engineers,
»Croatian Forestry« Ltd. Zagreb, Croatian Forestry
Society, Forestry Sciences Academy and CROJFE
(Croatian Journal of Forest Engineering).
The main objectives and reasons for the organization of this international Symposium are:
Þ Presentation of the latest results, up to date achievements and new ideas emerging in the area of
forest engineering and in the area of planning
forest operations;
Þ Promotion of cooperation and exchange of knowledge and experience among forestry scientists,
researchers and practitioners.
Topics and key dates of the Symposium
When defining and selecting the main topics of
the Symposium, the aim was to cover all areas significant for the works related to wood harvesting,
Croat. j. for. eng. 33(2012)1
Committees and bodies
As a large number of applicants and hence also a
large number of participants is expected at the Symposium (more than 200), it was extremely important
to gather a team of professionals and hard working
people ready to take over the responsibility for the
whole organization of the Symposium. Here are the
most important committees and their members whom
we thank for their engagement and help.
1
T. Pentek et al.
Looking Forward to the 45th International Symposium FORMEC 2012 (1–3)
Organizational Committee (in alphabetical order):
1. MSc. Ivan I{tok (President of the Committee
for Scientific Research of Croatian Forest Ltd.),
2. Prof. Dubravko Horvat (Faculty of Forestry
University of Zagreb, Croatia),
3. Assoc. Prof. Vladimir Jambrekovi} (Faculty of
Forestry University of Zagreb, Croatia),
4. Prof. Josip Margaleti} (Faculty of Forestry University of Zagreb, Croatia),
5. Assoc. Prof. Tibor Pentek (Faculty of Forestry
University of Zagreb, Croatia) – President,
6. Assoc. Prof. Tomislav Por{insky (Faculty of
Forestry University of Zagreb, Croatia) – Vice
President,
7. Assist. Prof. Mario [por~i} (Faculty of Forestry
University of Zagreb, Croatia),
8. Assoc. Prof. Marijan [u{njar (Faculty of Forestry University of Zagreb, Croatia),
9. MSc. Slivija Zec (General Secretary of Croatian
Chamber of Forestry and Wood Technology
Engineers).
Scientific Committee (in alphabetical order):
1. Prof. Antti Asikainen (The Finnish Forest Research Institute, Finland),
2. Prof. Raffaele Cavalli (University of Padua,
Italy),
3. Prof. Hans Rudolf Heinimann (Swiss Federal
Institute of Technology Zürich, Switzerland),
4. Prof. Tadeusz Moskalik (Warsaw Agricultural
University, Poland),
5. Assoc. Prof. Tibor Pentek (Faculty of Forestry
University of Zagreb, Croatia),
6. Assoc. Prof. Tomislav Por{insky (Faculty of
Forestry University of Zagreb, Croatia),
7. Prof. Karl Stampfer (University of Natural Resources and Life Sciences Vienna, Austria),
8. Assoc. Prof. Rien Visser (University of Canterbury, New Zealand),
9. Prof. Igor Poto~nik (University of Ljubljana,
Slovenia.
Honorary Committee:
1. Prof. Karl Stampfer (FORMEC President),
2. Prof. Milan Or{ani} (Dean of Faculty of Forestry University of Zagreb),
3. Prof. Hans Rudolf Heinimann (IUFRO Coordinator Division 3),
4. MSc. Damir Felak (President of Croatian Chamber of Forestry and Wood Technology Engineers),
5. Academic Slavko Mati} (President of the Forestry Sciences Academy),
6. Mr. sc. Petar Jurjevi} (President of Croatian Forestry Society).
2
Schedule of events and further activities
of the Organizational Committee
In the months to come, the Organizational Committee will develop the network website that should
be completed by the end of 2011, and the defined
domain of the official network website of FORMEC
2012 will be www.formec2012.hr.
All eminent experts, who are directly or indirectly
connected with the international scientific FORMEC
network, will be contacted through the Symposium
first announcements, which will be sent by standard
and/or electronic mail.
More than 200 participants from the country and
abroad are expected to attend the Symposium
FORMEC 2012 and more than 90 scientific papers
and more than 50 posters from different forestry
fields will be presented. At this Conference, after the
opening ceremony and plenary session, at which the
invitation (introductory) papers will be presented,
Table 1 Program of the international Symposium FORMEC 2012
Time
16:00–19:00
19:00
7:30–9:00
9:00–10:00
10:00–10:30
10:30–12:45
12:45–14:15
14:15–16:15
16:15–16:45
16:45–18:45
20:00
8:00–10:00
10:00–10:30
10:30–12:30
12:30–14:30
14:30–16:30
17:00–19:00
8:00–10:00
10:00–10:30
10:30–12:15
12:15–13:00
13:00–15:00
15:00–19:00
20:00
7:00
Event
Event location
Monday, Oct. 8, 2012
Symposium registration
Reception, hotel lobby
Welcome party
Tuesday, Oct. 09, 2012
Symposium registration
Reception, hotel lobby
Opening ceremony
Ragusa hall
Coffee break
Hotel terrace
Plenary session
Ragusa hall
Restaurant Cavtat
Lunch
Bobara, Orlando and [ipun halls
Work in sessions (3)
Coffee break
Hotel lobby
Poster section + discussion
Silent salon
VIP Dinner
Steak House
Wednesday, Oct. 10, 2012
Bobara, Orlando and [ipun halls
Work in sessions (3)
Coffee break
Hotel lobby
Bobara, Orlando and [ipun halls
Work in sessions (3)
Lunch
Restaurant Cavtat
Bobara, Orlando and [ipun halls
Work in sessions (3)
Field trip 1 (Cavtat or free afternoon)
Cavtat
Thursday, Oct. 11, 2012
Bobara, Orlando and [ipun halls
Work in sessions (3)
Coffee break
Hotel lobby
Plenary session
Ragusa hall
Conclusions and closing ceremony
Ragusa hall
Lunch
Restaurant Cavtat
Field trip 2 (Dubrovnik – Old Town)
Dubrovnik
Farewell party
Restaurant in Dubrovnik (Old Town)
Friday, Oct. 12, 2012
Departure of the participants
Croat. j. for. eng. 33(2012)1
Looking Forward to the 45th International Symposium FORMEC 2012 (1–3)
the activities will be carried out in three, or four sessions (depending on the number of registered and
accepted papers). The event schedule will be organized in accordance with the preliminary program.
Due to the importance of this Conference for the
forestry science and forestry practice, and due to a
large number of leading scientists and experts who
will present the latest results of their research and
Croat. j. for. eng. 33(2012)1
T. Pentek et al.
professional work, most of which is applicable in
practice, we would like to thank, in the name of the
Organizational Committee and personally, all who
have already, or will, make the Symposium FORMEC
2012 still better by their engagement, knowledge or
presence.
Tibor Pentek, Tomislav Por{insky, Ivica Papa
3
T. Pentek et al.
4
Looking Forward to the 45th International Symposium FORMEC 2012 (1–3)
Croat. j. for. eng. 33(2012)1
Original scientific paper – Izvorni znanstveni rad
Application of a Sugarcane Harvester for
Harvesting of Willow Trees Aimed at Short
Rotation Forestry: an Experimental Case
Study in Japan
Takuyuki Yoshioka, Katsuaki Sugiura, Koki Inoue
Abstract – Nacrtak
An experiment on the growing and harvesting of willow trees aimed at short rotation forestry was conducted in northern Japan. Willows were harvested using a sugarcane harvester
from southern Japan during its agricultural off-season. The growing experiment showed the
high potential of willow plantations to produce woody biomass of more than 10 dry-t/ha/y.
The harvesting experiment showed that space for turning around, one line in one row as a
planting method, a growing cycle of three years, and an extractor fan in the harvester are
necessary for mechanical harvesting. Mechanical harvesting was considered to have little
influence on willow regeneration provided that the machine cut reasonably well-grown
trees. The system performance of harvesting and collecting willow billets in a hypothetical
model field was calculated as 22.4 m3/h, suggesting the feasibility of supplying low-cost
wood chips.
Keywords: harvesting, Japan, short rotation forestry, sugarcane harvester, willow
1. Introduction – Uvod
Short rotation forestry (SRF), where fast-growing
tree species such as eucalypt, poplar, and willow are
reforested by planting rooted cuttings and repeatedly
harvesting the sprouting stumps in short-term cycles
of several years, has mainly been applied for producing pulp chips (Culshaw and Stokes 1995, Hartsough
et al. 2000, Stokes and Watson 1991). In recent years,
however, SRF has attracted attention worldwide as a
new source of woody biofuel. Commercial willow
plantations have been cultivated for bioenergy purposes in Sweden since the 1980s, and around 16,000
ha of short rotation willow plantations were established domestically from 1986 to 2000 (Mola-Yudego
2011). Other European countries and North America
have been testing harvesting operations using agricultural and forestry machines aimed at SRF (Spinelli
and Hartsough 2001, 2006, Spinelli et al. 2007, 2008,
2009, Volk and Luzadis 2009). Similarly in Japan,
woody biomass from SRF is defined as an »energy
crop« and is considered as a resource in the BioCroat. j. for. eng. 33(2012)1
mass-Nippon Strategy alongside »unused biomass«
such as logging residues (Anonymous 2005).
This paper outlines an experimental project for
growing, harvesting, and utilizing willow trees in
Japan. The project is currently underway in the boreal
forests of Hokkaido prefecture, northern Japan, and
has the following four objectives: (1) bioethanol production from willow tree chips; (2) effective utilization of abandoned agricultural land; (3) soil remediation; and (4) job creation. The growing period of
Salix schwerinii and S. sachalinensis, which are indigenous willow species of Hokkaido, is estimated to be
three years, and a high annual yield of 10 dry-t/ha/y
is expected even with intensive cultivation. A sugarcane harvester from Okinawa prefecture in southern
Japan was used for harvesting the willow trees; the
machine was shipped a distance of more than 2,000
km to the test site during the agricultural off-season
in Okinawa.
The usual operation of the sugarcane harvester is
as follows: (1) the basecutter cuts the sugarcane at
ground level and helps to feed the cane stalks to the
5
Takuyuki Yoshioka et al.
Application of a Sugarcane Harvester for Harvesting of Willow Trees ... (5–14)
butt lift roller; (2) the butt lift roller lifts the cut sugarcane stalks and guides them into the machine feed
rollers; (3) the feed rollers transport and horizontally
feed the cane stalks to the chopper drums; (4) the
chopper drums cut the sugarcane and send the billets
to the extractor chamber; (5) the primary extractor
cleans the billets by removing vegetable and mineral
impurities; and (6) the removable net container receives the sugarcane billets from the chopper. Regarding the use of a sugarcane harvester for other crops
in Japan, Kobayashi et al. (2003) made machine modifications for harvesting kenaf (Hibiscus cannabinus)
and examined its performance, and Iwasaki et al.
(2007) conducted tests for harvesting wood species.
The main purpose of this study was to examine
the feasibility of applying a sugarcane harvester to
harvest willow trees aimed at SRF. In the growing
experiments, growth increments of willows under
boreal conditions and cultivation methods to increase the increment were investigated, while methods
of land reclamation, planting, and cultivation appropriate for mechanical harvesting were discussed
through the harvesting experiments. Operational efficiency and fuel consumption of the harvester were
measured, and the influence of mechanical harvesting
on willow regeneration by sprouting was evaluated.
2. Material and Methods – Materijal
i metode
Three years after planting, which was the growing period in the project, the average annual increment for two years was calculated in the compartment where cut-back was performed, while the average annual increment for three years was calculated
in the compartment where cut-back was not performed, and the two increments were compared. As
0.5 × 0.5 m and 1.0 × 0.5 m indicate the spacing
between rooted cuttings, the planting density was
40,000 and 20,000 stumps per hectare, respectively.
2.3 Harvesting experiment – Pridobivanje
energijskoga drva
The experiment was carried out using a crawler-type sugarcane harvester (Fig. 1, UT-100K, Uotani-tekkou, Inc., Japan). Its engine output was 78 kW/
2,200 rpm and the cubic capacity of its removable net
container (Fig. 2) was 2.5 m3. The basecutter of the
harvester consisted of two rotary discs with four
chopper blades attached to each disc. The machine
was used to harvest willow trees in the manner
described above, and then was moved to a landing
for unloading when the container was filled with
willow billets. A time study was conducted during
the experiment with the following work elements:
moving with no load, cutting, turning around, moving fully-loaded, unloading, hooking up a container,
and others. The cutting length of the willow billet
was set to 25 cm, and so the harvested willows
required secondary chipping in order to be used as
fuel for direct combustion equipment such as a boiler.
2.1 Experimental site – Mjesto istra`ivanja
The growing experiments were carried out at two
sites in northern Hokkaido (NH) and eastern Hokkaido (EH). Three other sites were established for
harvesting experiments; two in NH and one in
northeastern Hokkaido (NEH), where indigenous
willows grow naturally and a site was prepared by
leaving rows of willow trees and cutting other ones
(see the NEH site in Fig. 3).
2.2 Growing experiment – Uzgojni pokus
In order to compare the yields per unit area by
performing or not performing cut-back and the difference in planting density (0.5 × 0.5 m and 1.0 × 0.5 m),
growing compartments for S. schwerinii and S. sachalinensis were made in the NH and EH sites, i.e., there
were 16 compartments in total, and 30 rooted cuttings of five clones were planted in each compartment. Cut-back, which means cutting shoots near
the ground after defoliation in the year of plantation,
is expected to encourage more shoots to sprout in the
following spring and thus increase the productivity
of the site.
6
Fig. 1 Sugarcane harvester
Slika 1. Kombajn za {e}ernu trsku
Croat. j. for. eng. 33(2012)1
Application of a Sugarcane Harvester for Harvesting of Willow Trees ... (5–14)
Takuyuki Yoshioka et al.
Table 1 Outline of the three test sites
Tablica 1. Opis triju istra`ivanih radili{ta
NEH
Age, years
Dob, godine
Number of row
Broj redova
Length of row, m
Du`ina reda, m
Space for turning around
Prostor za okretanje
Planting method (in one row)
Metoda sadnje (u jednom redu)
Planting density, stumps per 100 m2
Gusto}a sadnje, biljaka po 100 m2
Extractor fan of the harvester
Separator na kombajnu
NH
Ichi A
Ichi B
Ichi C
Sanru A
Sanru B
3–5
2
2
2
3
3
12
13
8
8
10
10
100
65
65
65
80
80
Wild-grown
Prirodan
No
Ne postoji
Two lines*
Dva reda*
No
Ne postoji
Two lines**
Dva reda**
No
Ne postoji
Two lines***
Dva reda***
No
Ne postoji
One line
Jedan red
No
Ne postoji
One line
Jedan red
102 ± 25.9
136
72
68
100
100
Running
Uklju~en
Running
Uklju~en
Running
Uklju~en
Running
Uklju~en
Running
Uklju~en
Non-running
Isklju~en
5m
*dense – gusto, **sparse – rijetko, ***staggered – naizmjeni~an
Fuel consumption was measured during the experiment, and the weight of each filled container was
measured by truck scale and then converted to dry
weight by estimating the water content of the billets.
In the experiment, the following elements were
examined: operational efficiency and fuel consumption according to the presence or absence of space for
turning around, planting method (one line or two
lines in one row), planting density, and running or
non-running of an extractor fan. The outline and
design of the three test sites are shown in Table 1 and
Fig. 3, respectively. There were two sites in NH:
Ichi-no-hashi (NH-Ichi) and Sanru (NH-Sanru); three
compartments were made at the NH-Ichi site and
two at the NH-Sanru site. Due to the wild willows
growing in the NEH site, the age of the trees varied
(3 to 5 years old, see Table 1) so there were some trees
with a diameter at ground level exceeding 10 cm. In
addition, since the density of stumps per unit area
differed for each row in the NEH site, the influence
of planting density on the machine cutting speed
was also examined throughout the experiment.
2.4 Investigation on regeneration by sprouting
Istra`ivanje vegetativne obnove
Willow stumps can be damaged when a sugarcane harvester cuts the trees, leading to concerns
about adverse effects on growth in the following
year. Tearing of stumps by cutting and regeneration
by sprouting were investigated by setting four plots
in the NEH site; the length and width of the rows in
each plot were 5 m and 2 m, respectively.
3. Results – Rezultati
3.1 Growing experiment – Uzgojni pokus
Fig. 2 Removable net container
Slika 2. Odvojivi spremnik
Croat. j. for. eng. 33(2012)1
Table 2 lists the results: regardless of planting
density, willow species, or test site, the average annual increment of the compartment where cut-back
7
Takuyuki Yoshioka et al.
Application of a Sugarcane Harvester for Harvesting of Willow Trees ... (5–14)
Fig. 3 Design of the three test sites
Slika 3. Nacrt triju istra`ivanih radili{ta
Table 2 Results of the growing experiment, dry-t/ha/y
Tablica 2. Rezultati uzgojnoga pokusa, tona suhe tvari po hektaru godi{nje
Planting density
Gusto}a sadnje
0.5 × 0.5 m
1.0 × 0.5 m
Salix schwerinii
NH site
EH site
NH site
EH site
No
0.60
8.84
4.70
10.28
Yes
0.93
11.80
5.06
16.03
No
Yes
1.67
9.32
2.89
7.56
3.23
12.11
4.18
9.00
was performed was higher than that where it was
not performed. In order to introduce this cut-back
practice, however, a method for cutting 20,000 or
40,000 shoots per hectare should be designed. Moreover, since the first harvesting operation itself functions as cut-back, there is no need for cut-back during
and after the second growing cycle. Taking cost-effectiveness into consideration, a decision must be
made on whether or not to perform cut-back.
In terms of planting density, the average annual
increment of the sparsely-planted compartment of S.
schwerinii was higher than that of the densely-planted
one, and vice versa in the case of S. sachalinensis, i.e.,
the densely-planted compartment produced a higher
yield than the sparsely-planted one. Salix sachalinensis and EH showed better results in terms of willow
8
Salix sachalinensis
Cut back
^epovanje
species and test site, respectively, but some of the
data on S. schwerinii in the NH site was significantly
low. Since the NH site was located in a water channel
area where gravelly soil was predominant, soil fertility might have been very poor in places. However,
the overall average annual increment was more than
6 dry-t/ha/y, and more than 10 dry-t/ha/y in the EH
site, showing the high potential of willow plantations
as woody biomass even in northern Japan.
3.2 Harvesting experiment – Pridobivanje
energijskoga drva
The results of the time study are shown in Fig. 4,
and the relationship between planting density and
cutting speed in Fig. 5. The stock of removable net
containers prepared for the experiment ran out in
Croat. j. for. eng. 33(2012)1
Application of a Sugarcane Harvester for Harvesting of Willow Trees ... (5–14)
Takuyuki Yoshioka et al.
Table 3 Average operating time of work elements
Tablica 3. Prosje~ni utro{ci vremena po radnim sastavnicama
Work element
Radna sastavnica
Turning around (smoothly)
Okretanje (bez pote{ko}a)
Turning around (with difficulty)
Okretanje (s pote{ko}ama)
Unloading
Istovar
Hooking up a container
Prikap~anje spremnika
Number
Veli~ina uzorka
Avg., sec/cycle
Ar. sredina, s/tura
SD, sec/cycle
Stan. devijacija, s/tura
23
26.5
8.45
22
60.5
17.0
16
49.7
18.2
15
93.7
23.9
the NH-Sanru B compartment, so the operation was
continued without containers. As a result, the operating times for unloading and hooking up a net container in NH-Sanru B in Fig. 4 are short.
The percentage of the operating time for turning
around to the total observed time was low in the
NEH site, while that in the NH-Ichi and NH-Sanru
sites was higher; this difference was due to the presence or absence of space for turning around (see
Table 1). The average operating time of the work elements in Table 3 shows that turning around with dif-
ficulty took twice as long as turning around smoothly,
suggesting the importance of space for turning
around when considering introducing mechanical
harvesting.
The correlation coefficient between planting density and cutting speed in Fig. 5 is calculated as –0.246,
so there is no clear correlation at the 0.05 significance
level. In terms of cutting speed in each test site, NEH
(3- to 5-year-old trees) was 28.3 m/min (standard deviation (SD) = 5.25 m/min), NH-Ichi (2-year-old trees)
was 41.2 m/min (SD = 11.0 m/min), and NH-Sanru
(3-year-old trees) was 36.8 m/min (SD = 6.55 m/min),
showing a trend in which the cutting speed decreases roughly in proportion to the tree age (or diameter
at ground level). During the experiment, the operator
controlled the cutting speed of the harvester since
Fig. 4 Results of the time study
Slika 4. Rezultati studija rada i vremena
Fig. 5 Relationship between planting density and cutting speed
Slika 5. Odnos izme|u gusto}e sadnje i brzine sje~e
Croat. j. for. eng. 33(2012)1
9
Takuyuki Yoshioka et al.
Application of a Sugarcane Harvester for Harvesting of Willow Trees ... (5–14)
the machine often could not pick up and »swallow«
cut willows when the speed was raised. Concerning
this cutting loss problem, the machine was found to
have difficulty in swallowing willow branches that
jutted to the side. Especially in the NH-Ichi site where
rooted cuttings were planted with two lines in one
row (the width between the two lines was 0.6 m, see
Fig. 3), the rows of the willow plantation were wider
than the horizontal clearance of the »mouth« of the
harvester. Therefore, for mechanical harvesting, one
line in one row appears to be a desirable planting
method.
The operating times for »others« in Fig. 4 were as
follows. The operation stopped in the NEH site because four willows, two of which were 9 cm in diameter at cutting height and the other two were >10 cm,
were too thick for the machine to cut down. After the
experiment, the operator reported that the maximum diameter of willow that the machine could cut
down was considered to be 7 cm, suggesting that a
growing cycle of three years is appropriate for mechanical harvesting. On the other hand, one of the
basecutter blades had to be repaired because the
machine »bit« stones in the gravelly soil in the NH-Sanru B compartment. Since the cutting height can
be adjusted from the operator’s seat, the height was
raised during the experiment in order to avoid
breaking the blades. In NH-Sanru B, however, the
cutting height of the crawler-type harvester varied
due to the rough ground and the machine dug up
stones in the soil. Consequently, for harvesting willow trees mechanically, land for cultivation should
be reclaimed. Furthermore, a sugarcane harvester is
designed to cut sugarcane at 5 cm below ground
level, so the basecutter must be improved for application to willow harvesting.
Table 4 lists the fuel consumption and weight of
harvested willows per hour and the weight per container (the weight per hour in NH-Sanru B is not
calculated due to the shortage of containers, as mentioned above). In the NH-Sanru site, where the running (NH-Sanru A) or non-running (NH-Sanru B) of
the extractor fan was examined, there was no difference between the NH-Sanru A and B compartments
in terms of fuel consumption. However, the weight
of harvested willows per container in NH-Sanru B
was less than that in NH-Sanru A; many tops and
branches dropped into the net container in NH-Sanru
B because the extractor fan stopped during the operation. In view of the importance of gathering wood
fiber as well as returning minerals to the soil, the fan
should be operated.
3.3 Investigation on regeneration by sprouting
Istra`ivanje vegetativne obnove
Fig. 6 shows the number of torn and intact stumps
and the rate of regeneration by sprouting according
to the diameter at cutting height. Although tearing
of stumps was observed in every diameter class
thicker than 15 mm, all of the torn stumps at the plots
sprouted. The rate of regeneration was proportional
to the diameter, and all of the stumps with diameters
thicker than 30 mm also sprouted. Therefore, provid-
Table 4 Fuel consumption and weight of harvested willows per hour
and weight per container
Tablica 4. Potro{nja goriva i masa posje~ene vrbe po satu rada te po
spremniku
Site
Radili{te
NEH
NH-Ichi A
NH-Ichi B
Weight of harvested Weight per container,
Fuel
dry-t/container
consumption, willows per hour,
dry-t/h
L/h
Masa posje~ene vrbe,
Potro{nja Masa posje~ene vrbe, tona suhe tvari po
spremniku
goriva, L/h tona suhe tvari po satu
10.05
1.92
0.369
11.12
0.72
0.260
14.54
0.76
0.280
NH-Ichi C
13.51
0.71
0.207
NH-Sanru A
12.00
0.324
NH-Sanru B
12.73
1.26
–
10
0.260
Fig. 6 The number of torn and intact stumps and the rate of regeneration
by sprouting
Slika 6. Broj odsje~enih i preostalih stabala te stupanj vegetativne obnove
Croat. j. for. eng. 33(2012)1
Application of a Sugarcane Harvester for Harvesting of Willow Trees ... (5–14)
Takuyuki Yoshioka et al.
ed that reasonably well-grown trees are cut, mechanical harvesting is considered to have little influence
on willow regeneration.
4. Discussion – Rasprava
Regarding the operational efficiency of the sugarcane harvester, the weight of harvested willows per
hour listed in Table 4 is low and unsatisfactory, so
machine productivity in a hypothetical model field
is discussed. A model field of 270 m in length and
180 m in width is considered here (Fig. 7) and is a
typical agricultural compartment in Hokkaido. It is
assumed that a sugarcane harvester harvests willows
and a forwarder collects removable net containers
filled with willow billets. The following assumptions are also made:
Þ Four strip roads for the forwarder are set up in
the field, and the width of each road is 5 m. Data
on the cutting speed in NH-Sanru (36.8 m/min)
and the weight of harvested willows per container in NH-Sanru A (0.324 dry-t/container, see
Table 4) are used here, while the operating times
for turning around smoothly (26.5 sec/cycle), unloading (49.7 sec/cycle), and hooking up a container (93.7 sec/cycle) in Table 3 are also used;
Þ The growing stock of willows per hectare at the
time of harvesting is 30 dry-t/ha when the growing cycle and the annual increment are three years
and 10 dry-t/ha/y, respectively, and the planting
area is 4.50 ha (= 180 × 250 m) in consideration of
the right-of-way of the four 5-m-wide strip roads.
Therefore, the growing stock in the field is calculated as 135 dry-t;
Þ The rows of willow trees are spaced at 1.8-m intervals for mechanical harvesting and perpendicular to the strip roads, so there are 100 rows
(= 180/1.8) in the field; the growing stock in one row
is thus calculated as 1.35 dry-t/row (= 135/100);
Þ One cycle of the sugarcane harvester consists of
cutting, unloading on a strip road, and hooking
up a container. The harvester turns around once
every four cycles;
Þ Although the weight of harvested willows per
container of 0.324 dry-t/container is slightly less
than that of the growing stock to be harvested in
one cycle (= 1.35/4), the cutting loss during operation is considered;
Þ The forwarder collects four containers in one cycle
and unloads them alongside a public road on the
right side of the model field. The average running
distance per cycle is 180 m; the running speed is
estimated as 90 m/min, and the operating time
for loading and unloading is each estimated as
1 min/container, i.e., 4 min/cycle.
Croat. j. for. eng. 33(2012)1
Fig. 7 Hypothetical model field
Slika 7. Teorijski model radnoga polja
As a result, the operational efficiency of the sugarcane harvester and the system performance in the
model field are calculated as follows:
Þ In terms of harvesting, the operations of cutting
(36.8 m/min, i.e., 101.9 sec/cycle), unloading
(49.7 sec/cycle), and hooking up a container
(93.7 sec/cycle) are carried out 400 times (98,120
seconds in total), while the operation of turning
around (26.5 sec/cycle) is carried out 100 times
(2,650 seconds in total). The total operation time
is 100,770 seconds, so the operational efficiency
of the harvester is calculated as: 0.324 × 400 ×
(3,600 / 100,770) = 4.63 dry-t/h
Þ Considering the running speed of 90 m/min, i.e.,
avg. 2 min/cycle and the operating times for
loading and unloading of 4 min/cycle in each,
the one cycle of a forwarder takes 10 minutes, so
the operational efficiency of the forwarder is calculated as: 0.324 × 4 × (60 / 10) = 7.78 dry-t/h
When the forwarder operates in parallel with the
harvester, the system performance is calculated
as: 4.63 × 7.78 / (4.63 + 7.78) = 2.90 dry-t/h
The system discussed here has the following four
advantages: (1) capacity for handling narrow interrows; (2) tracked configuration allowing traversing
11
Takuyuki Yoshioka et al.
Application of a Sugarcane Harvester for Harvesting of Willow Trees ... (5–14)
of soft or steep terrain; (3) unitization of the product
in bags, which allows independent harvesting and
extraction, with all related benefits; and (4) better
storage quality of billets compared to chips.
The average productivity of a sugarcane harvester with the same engine output as the studied one is
6.4 wet-t/h when harvesting sugarcane (from personal communications with an engineer from the
machine manufacturer and a researcher from the
Okinawa Prefectural Agricultural Research Center).
Therefore, considering the water content of willow
billets (about 120% on average on a dry-weight
basis), it is expected that the performance of the
sugarcane harvester in harvesting willows can be as
much as that in harvesting sugarcane.
The system performance of 2.90 dry-t/h corresponds to 22.4 m3/h of willow billets in volume. In
order to discuss willow plantations as SRF, in principle, the cultivation process, e.g., reclamation of
land, preparation of rooted cuttings, and application
of fertilizer, should be considered in addition to the
forwarding and collecting processes. However, a
supply of low-cost willow chips could be achieved
by introducing large, efficient transporting and chipping machines such as trailers and tub grinders.
5. Conclusions – Zaklju~ci
In this study, an experiment on growing and harvesting of willow trees aimed at short rotation forestry was conducted in northern Japan. Willows were
harvested using a sugarcane harvester from southern Japan during its agricultural off-season. The following conclusions are drawn:
Þ The growing experiment showed the high potential of willow plantations to produce woody biomass of more than 10 dry-t/ha/y;
Þ The harvesting experiment showed that space for
turning around, one line in one row as a planting
method, a growing cycle of three years, and an
extractor fan in the harvester are necessary for
mechanical harvesting;
Þ Mechanical harvesting was considered to have
little influence on willow regeneration provided
that the machine cut reasonably well-grown trees;
Þ The system performance of harvesting and collecting willow billets in a hypothetical model field
was calculated as 22.4 m3/h, suggesting the feasibility of supplying low-cost wood chips.
12
6. References – Literatura
Anonymous, 2005: Biomass-Nippon Strategy (provisional
translation): Decided at the Cabinet Meeting, Government
of Japan, December 27, 2002, Biomass and Bioenergy 29(5):
375–398.
Culshaw, D., Stokes, B., 1995: Mechanisation of short rotation forestry. Biomass and Bioenergy 9(1–5): 127–140.
Hartsough, B., Spinelli, R., Pottle, S., Klepac, J., 2000: Fiber
recovery with chain flail delimbing/debarking and chipping of hybrid poplar. Journal of Forest Engineering 11(2):
59–68.
Iwasaki, K., Teraoka, Y., Sueyoshi, T., 2007: Development
of woody biomass harvesting system: Cutting characteristics of bishop wood. Journal of the Japanese Society of
Agricultural Technology Management 14(2): 81–85.
Kobayashi, Y., Otsuka, K., Taniwaki, K., Sugimoto, M.,
Kobayashi, K., 2003: Development of kenaf harvester and
characteristics of the performance. Japanese Journal of
Farm Work Research 38(2): 93–98.
Mola-Yudego, B., 2011: Trends and productivity improvements from commercial willow plantations in Sweden during the period 1986–2000. Biomass and Bioenergy 35(1):
446–453.
Spinelli, R., Hartsough B. R., 2001: Extracting whole short
rotation trees with a skidder and a front-end loader. Biomass and Bioenergy 21(6): 425–431.
Spinelli, R., Hartsough B. R., 2006: Harvesting SRF poplar
for pulpwood: Experience in the Pacific Northwest. Biomass and Bioenergy 30(5): 439–445.
Spinelli, R., Cuchet, E., Roux, P., 2007: A new feller-buncher for harvesting energy wood: Results from a European
test programme. Biomass and Bioenergy 31(4): 205–210.
Spinelli, R., Nati, C., Magagnotti, N., 2008: Harvesting
short-rotation poplar plantations for biomass production.
Croatian Journal of Forest Engineering 29(2): 129–139.
Spinelli, R., Nati, C., Magagnotti, N., 2009: Using modified
foragers to harvest short-rotation poplar plantations, Biomass and Bioenergy 33(5):817–821.
Stokes, B., Watson, W., 1991: Wood recovery with in-woods
flailing and chipping. TAPPI Journal 74(9): 109–113.
Volk, T. A., Luzadis, V. A., 2009: Willow biomass production for bioenergy, biofuels, and bioproducts in New
York. In: Renewable Energy from Forest Resources in the
United States (Solomon, B. D., Luzadis, V. A., eds.), Routledge, London and New York, p. 238–260.
Croat. j. for. eng. 33(2012)1
Application of a Sugarcane Harvester for Harvesting of Willow Trees ... (5–14)
Takuyuki Yoshioka et al.
Sa`etak
Primjena kombajna za {e}ernu trsku pri pridobivanju energijskoga vrbova drva iz
kultura kratke ophodnje: pokus u Japanu
U radu su prikazani uzgojni postupci, pridobivanje i upotreba energijskoga vrbova drva iz sastojina kratkih
ophodnji u sjevernom Japanu. Istra`ivane su dvije vrste vrba, Salix schwerinii E. Wolf. i Salix sachalinensis F.
Schmidt, koje su autohtone vrste na Hokkaidu. Za sje~u vrbovih stabala kori{ten je kombajn za {e}ernu trsku kako
bi se pove}ala njegova iskoristivost izvan sezone `etve {e}erne trske. Uzgojni postupci koji su provedeni u
istra`ivanju pokazali su da planta`e vrbâ imaju velik potencijal u proizvodnji suhe tvari, i to do 10 tona suhe tvari
po hektaru godi{nje, ~ak i uz intenzivnu primjenu uzgojno-tehni~kih mjera.
Cilj je ovoga istra`ivanja bio ispitati primjenjivost kombajna za {e}ernu trsku pri pridobivanju energijskoga
vrbova drva iz sastojina kratkih ophodnji. Pri provo|enju uzgojnih postupaka istra`ivan je prirast biljaka pod
utjecajem borealne klime, zatim uzgojne metode za pove}anje prirasta, dok su metode za melioraciju tla, sadnju i
uzgojni postupci pogodni za upotrebu mehaniziranoga pridobivanja drva raspravljeni u pokusima pridobivanja
drva. Uz to su istra`ivani u~inkovitost i potro{nja goriva, dok je utjecaj mehaniziranoga pridobivanja energijskoga
drva na vegetativnu obnovu sastojina samo procijenjen.
Postavljene su dvije pokusne plohe za uzgojne radove na sjevernom dijelu Hokkaida (NH) te dvije na isto~nom
dijelu (EH). Plohe su podijeljene u 16 odjeljaka na koje su posa|ene o`iljenice 30 razli~itih vrsta klonova.
Istra`ivani su gusto}a sadnje (0,5 × 0,5 ili 1,0 × 0,5) i utjecaj ~epovanja na proizvodnju drvne tvari. ^epovanje je
provedeno nakon prve godine. Nakon zavr{etka istra`ivanoga razdoblja od tri godine na odjeljcima gdje je
provedeno ~epovanje ra~unat je prosje~ni godi{nji prirast za dvije godine, dok je na odjeljcima gdje nije provedeno
~epovanje ra~unat prosje~ni godi{nji prirast za tri godine.
Pokusi pridobivanja energijskoga drva provedeni su na dvije pokusne plohe postavljene na sjevernom Hokkaidu
(NH), prva je ploha naknadno podijeljena u odjeljke Ich (A, B, C), dok je druga podijeljena na odjeljke Sanru (A, B);
uz to je postavljena jedna pokusna ploha na sjeveroisto~nom Hokkaidu (NEH) gdje istra`ivane vrbe rastu prirodno
(tablica 1, slika 3). Za pridobivanje energijskoga vrbova drva kori{ten je gusjeni~ni kombajn za {e}ernu trsku (slika
3) snage motora 78 kW pri 2200 okretaja. Princip je rada kombajna sljede}i: 1) sje~ivo sije~e trsku/drvo pri tlu; 2)
pomo}u sustava valjaka dovodi trsku/drvo do bubnja za sje~enje, koji je prilago|en tako da sije~e komade drva
du`ine do 25 cm; 3) nakon bubnja za sje~enje isje~ena trska/drvo dolazi u separator gdje se odvajaju biljne i
mineralne ne}isto}e (blato, sitne gran~ice koje se izbacuju nazad na proizvodnu povr{inu); 4) nakon separatora
komadi trske/drva ulaze u spremnik. Nakon {to se spremnik napuni, kombajn izlazi na pomo}no stovari{te te se
zamjenjuje spremnik. Spremnici su vagani pomo}u kamionskih vaga te se na osnovi toga izra~unala suha tvar na
osnovi procjene udjela vode u komadima vrbovine.
Tijekom istra`ivanja proveden je i studij rada i vremena s radnim elementima: kretanje s praznim spremnikom,
sje~a, okretanje, kretanje s punim spremnikom, istovar, prikap~anje praznoga spremnika i ostalo.
S obzirom na to da je kombajn sjekao komade drva du`ine do 25 cm, potreban je dodatni stroj (ivera~) kako bi se
dobio proizvod primjeren za upotrebu.
U tablici 2 prikazani su rezultati uzgojnih postupaka. Neovisno o gusto}i sadnje, vrsti vrbe ili istra`ivanoj
plohi, odjeljci gdje je provedeno ~epovanje imali su ve}i prosje~ni godi{nji prirast nego plohe gdje nije provedeno
~epovanje. Ovisno o gusto}i sadnje, plohe na kojima je Salix schwerinii E. Wolf sa|ena rje|im rasporedom sadnice
imale su ve}i prirast nego plohe na kojima je sa|ena gu{}e, dok je u slu~aju sadnje Salix sachalinensis F. Schmidt
situacija bila obrnuta. Prosje~ni je godi{nji prirast na svim plohama ve}i od 6 tona suhe tvari po hektaru, a na plohi
na isto~nom dijelu Hokkaida prirast je ve}i od 10 tona suhe tvari po hektaru godi{nje.
Na slici 4 prikazani su rezlutati studija rada i vremena, dok su na slici 5 prikazani rezultati ovisnosti gusto}e
sadnje o brzini sje~e. S obzirom na to da je na plohi NH Sanru B postojao nedostatak spremnika, vrijeme za istovar i
prikap~anje novoga spremnika je kra}e. Prosje~ni utro{ci vremena radnih sastavnica prikazani su u tablici 3, iz
~ega se mo`e i{~itati potreba za prostorom za okretanje kombajna. Odnos gusto}e sadnje i brzine sje~e prikazan je na
slici 5, za koji je izra~unat koeficijent korelacije – 0,246, {to zna~i da nema povezanosti za razinu zna~ajnosti od
0,05. U slu~aju brzine sje~e primije}eno je kako brzina ovisi o dobi biljaka, odnosno promjeru na panju.
U tablici 4 prikazana je potro{nja goriva, masa suhe tvari po satu te masa suhe tvari po spremniku. Na plohama
NH Sanru pra}ena je upotreba separatora, u odjeljku A je separator bio uklju~en, dok je u odjeljku B bio isklju~en.
Croat. j. for. eng. 33(2012)1
13
Takuyuki Yoshioka et al.
Application of a Sugarcane Harvester for Harvesting of Willow Trees ... (5–14)
Nije zamije}eno pove}anje potro{nje goriva, ali je uo~eno da su spremnici u odjeljku B imali manju masu zbog
neodvajanja sitnih gran~ica pomo}u separatora. U obliku prikupljanja drva, ali i vra}anja dijela hraniva u tlo
separator bi trebao biti uklju~en.
Na slici 6 prikazan je stupanj vegetativne obnove istra`ivanih ploha nakon provedene mehanizirane sje~e, koji
pokazuje da mehanizirana sje~a nema nikakav negativni utjecaj na vegetativnu obnovu vrbovih sastojina kratkih
ophodnji.
Kako su podaci iz tablice 4 o u~inku kombajna niski i nezadovoljavaju}i, rasprava se temelji na teorijskom
radnom polju prikazanom na slici 7, a koje predstavlja tipi~no radno polje na Hokkaidu. Za izra~un modela
kori{teni su podaci o brzini sje~e i masi punoga spremnika iz tablice 4, dok su vremena radnih sastavnica preuzeta
iz tablice 3. O~ekivana je zaliha na polju nakon ophodnje od 3 godine 135 tona suhe tvari po hektaru ili 1,35 tona u
jednom redu, koji su posa|eni na razmaku od 1,8 m. Forvarder u jednom ciklusu skuplja 4 spremnika i istovara ih
uz rub javne prometnice, a vrijeme ciklusa je 10 min. Na temelju teorijskoga modela dobivena je proizvodnost
kombajna od 4,63 tona suhe tvari po satu, dok je proizvodnost forvardera 7,78 tona suhe tvari po satu. Sustav
opisan ovdje posjeduje ~etiri prednosti: 1) mogu}nost rada u malom me|urednom razmaku; 2) gusjeni~ni kombajn
omogu}uje rad na nagnutom terenu; 3) mogu}nost pohrane proizvoda u vre}e, {to omogu}uje razdvajanje procesa
sje~e i izvo`enja i 4) bolja kakvo}a uskladi{tenih komada vrbe u usporedbi s iverjem.
U~inkovitost ovakva na~ina proizvodnje energijskoga drva od 22,4 m3/h upu}uje na mogu}nost pridobivanja
velikih koli~ina jeftinoga iverja.
Klju~ne rije~i: kulture kratkih ophodnji, vrba, kombajn za {e}ernu trsku, pridobivanje drva, Japan
Authors’ addresses – Adresa autorâ:
Received (Primljeno): December 9, 2011
Accepted (Prihva}eno): January 9, 2012
14
Assoc. Prof. Takuyuki Yoshioka, PhD.
e-mail: yoshioka@brs.nihon-u.ac.jp
Assist. Prof. Katsuaki Sugiura, PhD.
Prof. Koki Inoue, PhD.
Laboratory of Sustainable Forest Utilization
Department of Forest Science and Resources
College of Bioresource Sciences, Nihon University
1866 Kameino, Fujisawa 252-0880
JAPAN
Croat. j. for. eng. 33(2012)1
Original scientific paper – Izvorni znanstveni rad
Mechanized Harvesting of Eucalypt
Coppice for Biomass Production Using
High Mechanization Level
Rodolfo Picchio, Alessandro Sirna, Giulio Sperandio, Raffaello Spina, Stefano Verani
Abstract – Nacrtak
The main aims of this study were to determine the productivity, profitability and energy balance (output/input) of mechanized harvesting applied to a eucalyptus plantation in central
Italy. The study area was located in Rome, at an altitude of 35 m a.s.l., on a flat, even site
(average slope gradient 3%). The stand was a eucalypt coppice (Eucalyptus camaldulensis
Dehnh.) harvested for the first time in 2000. The planting pattern was square with 3 m
among stumps (1111 trees ha–1). By 2009, insect (Phorachantha semipunctata) attacks
had reduced stump density to 592 stumps ha–1. The work system applied was the Whole Tree
System (WTS) and the final assortement chips for energy. Machine rates were calculated using coefficients and mathematical formulas extracted from the main methodologies proposed
by different authors. Energy balance was estimated with the Gross Energy Requirements
(GER) method. In these plantations, mechanized harvesting seems most appropriate: this is
demonstrated by the high productivity recorded (PSH15 6.5 td.w. h–1 worker–1) and by the favorable energy balance (output/input 23.8, 95.8% system efficiency). However harvesting
cost is still high (44.30 € tf.w.–1) and can only be reduced through careful operational
planning.
Keywords: harvester; work productivity; operating costs; energetic balance; chipper; forwarder;
forest plantation
1. Introduction – Uvod
In Italy, eucalypt was used mainly for windbreaks
and reforestation, especially in the South and in the
Islands. Large reforestation programs were launched in 1950s mainly for soil protection purposes in
Southern Italy (Calabria and Sicily). Later on, in
1980s new projects were launched for the production
of pulpwood (Mughini 2000). Most popular Eucalypt species were E. globulus ssp. bicostata, E. globulus
ssp. globulus, E. occidentalis, E x trabutii, E. camaldulensis and E. viminalis. The surface of eucalypt plantations is now estimated at 72,000 hectares (54,000 ha
pure, 18,000 ha mixed with other species). Yields
vary a lot, depending on species and site. For instance, E. globulus ssp. globules may produce from 10 to
35 m3 ha–1 year–1, whereas E. occidentalis will produce
between 3 and 8 m3 ha–1 year–1 (Gemignani 1988).
The outlook for eucalypt plantations in Italy can be
summarized in three points:
Croat. j. for. eng. 33(2012)1
Þ naturalization of less productive plantations, especially in Southern Italy;
Þ intensification of crop modules for industrial
plantations, in order to increase both the quality
and quantity of production (medium rotation coppice and short rotation coppice for wood chips).
This will be done using selected clones;
Þ rationalized use in agroforestry, where row plantations can offer timber, firewood and wood chips.
Energy crops appear as a promising option for
ensuring bioenergy feedstock. The profitability of
energy crops is highly dependent on appropriate logistics, harvest planning and crop yield (Vega-Nieva
et al. 2008). The greatest potential for cost reduction
lies in mechanization, which may increase productivity with the introduction of innovative harvesting
equipment. Although stand management research
regarding the definition of proper practices is now
completed, there is always some potential for further
15
R. Picchio et al.
Mechanized Harvesting of Eucalypt Coppice for Biomass Production ... (15–24)
cost reduction (e.g. refinement of yield-response in relationships for various management practices). Many
experimental plots are now entering the coppice stage.
In many cases, the primary maintenance practice
consists of frequent harvesting that rejuvenates the
stand and stimulates fast growth. Traditional practices for harvesting fuel wood are labor intensive,
which may discourage maintenance causing the deplorable state of abandonment of many coppice stands
in industrialized countries (Spinelli et al. 2006). The
main aims of this study were to determine the productivity, profitability and energy balance (output/input) of mechanized harvesting applied to eucalyptus plantation in central Italy. In order to estimate the
energy balance, we determined: indirect inputs, i.e.
the energy used for equipment production; direct
inputs, i.e. fuel and oil consumption; and human
energy consumption during work; output, i.e. energetic value of total wood fuel produced.
These data were used to determine the economic
and energetic sustainability of mechanized harvesting chains. Over these last years, mechanization has
been rapidly introduced to forest operations. The
Italian harvester and processor fleet now counts over
84 units, and its number doubled in the last five years
(Spinelli et al. 2010). Although mechanized harvesting was originally designed and first applied to high
forest logging (poplar plantation, coniferous plantation), in recent years it has been employed for harvesting coppice stands. However, the smaller volume of coppice trees implies a lower productivity
(Martins et al. 2009). An adequate training of workers
and planners is necessary, especially when introducing mechanized harvesting to the sustainable
use of forest biomass, as a renewable source of clean
energy with reduced greenhouse gases (GHG) emission balance (Picchio et al. 2009).
The term »energy analysis« refers to the study of
the energy used for the production of a service or a
stock. Total energy use includes both the energy directly used during the production process (direct), and
the energy stocked in the materials used for the production process (indirect). The Gross Energy Requirements (GER) method is commonly used in energy
analyses (IFIAS 1975, Picchio et al. 2009). Although
the GER method and the ISO 14040 standard (UNI
EN ISO 14040 2006) do not include the assessment of
human energy input, man work is of relevant contribution in many production activities, such as forestry activities with low mechanization level. So for
a proper comparison between yards with high and
low mechanization levels, it will be appropriate to
put the human energy input in the energy balance of
all forestry yards, even if it represents a low percentage contribution to the total energy inputs. A basic
16
requirement for any bioenergy generation system is
that the energy produced (output) must be greater
than the inputs of non-renewable energy required to
establish and operate the system (Matthews 2001,
Picchio et al. 2009).
2. Materials and methods – Materijal
i metode
The study was carried out in Rome (41°54'32,55'' N,
12°21'32,34'' E). The study area was characterized by
mild climate and volcanic substrata (sand 60%; silt
20%; clay 20%). It had an elevation of 35 m a.s.l. and
its terrain was even and flat (average slope gradient
3%, maximum 10%).
The stand was a eucalypt coppice (Eucalyptus
camaldulensis Dehnh.) (Table 1) harvested for the first
time in 2000. The plantation was established in 1989;
trees were planted according to 3 m square pattern
(1111 trees ha–1). By 2009, insect (Phorachantha semipunctata) attacks had reduced stump density to
592 stumps ha–1.
Logging was conducted in summer 2009 on a
total area of about 2 ha. All area was surveyed with a
Trimble Juno ST GPS device. All operations were
carried out by the same private Forest Company. The
machines used were:
Þ one harvester John Deere (ex Timberjack) 1270 C
with a felling-processing head JD (ex TBJ) 762 C,
for felling and bunching the trees;
Table 1 Site characteristics
Tablica 1. Zna~ajke radili{ta
Place – Mjesto
Rome (Italy)
Surface, ha – Povr{ina, ha
1.72
Slope gradient, % – Nagib terena, %
3
Elevation, m a.s.l. – Nadmorska visina, m n. v.
35
Species – Vrsta drve}a
E. camaldulensis
Age in years – Dob u godinama
10
Density, stumps/ha – Gusto}a, panjeva/ha
592
Average DBH, cm – Prosje~ni srednji promjer, cm
12.9
Average height, m – Prosje~na visina, m
14.3
Average mass, tf.m. – Prosje~na masa, tf.m.
0.329
Average number of shoot per stump
3.6
Prosje~an broj izbojaka po panju
Average mass harvested, tf.m.ha–1
194.768
Prosje~na masa sje~e, tf.m.ha–1
Wood characteristics, chips – Zna~ajke drva, ivera
Bulk density, kg m–3 – Gusto}a, kg m–3
320
Moisture content, % – Udio vlage, %
37.59
Croat. j. for. eng. 33(2012)1
Mechanized Harvesting of Eucalypt Coppice for Biomass Production ... (15–24)
Þ one forest loader OP T80, to assist the harvester in
tree bunching;
Þ one forwarder JD (ex TBJ) 1100 with chipper Erjo
for chipping whole trees from bunches;
Þ one truck DAF CF 85.430 with trailer VIBERTI 7
LOMASS 22 R for chips transport.
There were two forestry operators. The work system applied was the Whole Tree System (WTS). Whole
trees were chipped at the stump site, and chips were
discharged directly into the transportation vehicles,
which could easily access the cutover.
The main dendrometric parameters (DBH and tree
height) were measured in 2 circular plots randomly
selected inside the stand (total surface 5652 m2). A t
test for independent samples was applied to each
dendrometric parameter and showed no significant
difference between the two plots (DBH n° 309,
p-value 0.079; height n° 97, p-value 0.647). A tree
caliper (Silvanus type 1208, accuracy 0.5 cm) was
used for measuring the diameter at breast height
(DBH) and a tape logger for determining tree height,
after felling. After the harvesting, the height of the
felled stump was measured in 2 rectangular plots
randomly selected (total surface 1200 m2). A t test
showed significant differences between two plots
(n° 134, p-value 0.0233).
Moisture content and wood density were determined on 30 wood discs (3 cm thick) collected randomly in each plot. The 60 wood discs were immediately weighed with a precision scale (Orma model
BC16D) and then taken to the laboratory for determining moisture and wood density, according to the
thermo-gravimetric method (UNI EN 13183-1 2003,
UNI ISO 3130 1985, UNI ISO 3131 1985, Lo Monaco
et al. 2011). Statistical analysis (Kruskal Wallis) showed no significant differences (wood density fresh
weight: KW 0.259, p-value 0.611; wood density dry
weight KW 0.188, p-value 0.665) between the two
plots.
For the conversion of volume into fresh mass, we
used the measured average density of 1.13 kg dm–3.
The top and branches were considered to be the 25%
of the stump mass. This figure was determined by
weighing the stem, the top and the branches of a
sample of 60 shoots, randomly selected on 60 different stumps.
The experimental data (felling/bunching and
chipping) were recorded for one hectare of plantation. To relate the felling time to tree mass, 110 stumps
(396 shoots) were numbered, randomly selected.
Slope gradient was measured with a clinometer
(Meridian MI 4007). Work time was recorded for
every single phase, using a chronometric table Minerva equipped with three centesimal chronometers
Croat. j. for. eng. 33(2012)1
R. Picchio et al.
(Anon. 1988, Harstela 1991, Berti et al. 1989, Savelli
et al. 2010). In order to calculate outputs in different
plots, effective time and delays in the work routine
up to 15 min (UT, unavoidable time and AT, avoidable time) (Anon. 1988, Harstela 1991, Picchio et al.
2009) were recorded.
Based on work times, volume and mass, the productivity per worker for the different operations was
calculated as: average gross productivity (PHS15),
measured on the basis of time consumption, inclusive of all delays up to the maximum event duration
of 15 minutes; average net productivity (PHS0), computed with the exclusion of delays.
The cycle times of the machines were divided
into time elements (process steps) that were considered typical of the work.
Harvester time consisted of: positioning, beginning when the machine approached the stump and
ending when the machine head rested on a tree; felling, beginning when the felling cut started and ending when the tree touched the ground; bunching,
beginning when the tree touched the ground and
ending when the tree was dropped onto a bunch.
Loader time consisted of bunching the tree that the
harvester was not able to pile; beginning when the
tree was taken from the loader and ending when the
tree was put on the pile.
Chipping time consisted of: positioning, i.e. the
time necessary for the truck to approach the chipper
and park by its side; chipping, i.e. the time during
which the chipper produced the chips; moving the
time necessary for the truck and the chipper to approach a bunch of trees. For all operations, delay was
also recorded, i.e. the time during which the machine was not engaged in any productive work process (e.g. repair and/or maintenance, rest, etc.).
The influence of tree weight on the felling time
was estimated by linear regression, calculated with a
regression analysis.
Total labor cost (including taxes and all social
costs) was 23 € h–1 for the harvester operator and the
chipper operator, whereas the loader operator cost
was 15 € h–1. Stumpage was 15 € t–1. Fuel cost was
assumed at July, 2009. Machine rates (Table 2) were
estimated using the coefficients and the mathematical formulas already applied by many authors (Miyata 1980, Picchio et al. 2011a, Spinelli et al. 2011).
Further details on cost calculation are reported in
Table 2.
The energy balance was estimated with the GER
method (IFIAS 1975, Picchio et al. 2009). It was used
to estimate the direct and indirect input requirements for the machinery used as showed by Picchio
et al. 2009. Furthermore, by an indirect method to
assess the energy expenditure in forestry operations
17
R. Picchio et al.
Mechanized Harvesting of Eucalypt Coppice for Biomass Production ... (15–24)
Table 2 Principal calculation elements and machine costs
Tablica 2. Glavne sastavnice izra~una i tro{kovi strojeva
Description
Stavka
Purchase price – Nabavna cijena
Salvage value* – Preostala vrijednost*
Service life – Vrijeme trajanja
Annual usage – Godi{nja uporaba
Power – Snaga
Interest rate – Kamatna stopa
Fuel consumption – Potro{nja goriva
Lubricant consumption – Potro{nja maziva
Garage space – Gara`ni prostor
Labor cost – Tro{ak radnika
Fuel cost – Tro{ak goriva
Lubricant cost – Tro{ak maziva
Fixed Costs – Fiksni tro{kovi
Variable Costs – Varijabilni tro{kovi
Total machine Costs (included labour cost)
Ukupni tro{kovi stroja s tro{kom radnika
Unit of measure
Mjerna jedinica
€
€
y
H
kW
%
l h–1
l h–1
m2
€ h–1
€ l–1
€ l–1
€ h–1
€ h–1
€ h–1
Loader OP T80
380,000
84,094
10
1,200
173
5
15
0.6
35
23
1.04
9
41.56
66.31
Chipper Eryo on
Forwarder (JD 1100)
520,000
115,076
10
800
440(+118)
5
35
1.4
45
23
1.04
9
88.12
114.93
107.87
203.05
71.77
JD 1270 c Advance
127,000
20,786
12
600
132
5
13
0.52
23
15
1.04
9
24.20
47.57
(*) The salvage value was calculated by multiplying the purchase price for 0.86N, where N = service life of the machine
(*) Vrijednost na kraju vremena kori{tenja izra~unata je uve}avanjem nabavne cijene za 0,86N, gdje je N = vrijeme kori{tenja stroja
in situ (Scott and Christie 2004, Christie 2008) human
energy consumption was estimated, on the basis of a
human heart-rate response during field work. The
two workers were assessed for five work day. Minute-to-minute heart rate was recorded using a Polar
heart rate monitor during the test in order to calculate the predicted energy expenditure from working
heart rate responses on the basis of individual regression equations. This technique has been validated by several authors (Haskell et al. 1992, Scott and
Christie 2004, Strath et al. 2001).
To calculate the energy output, the Higher Heating Value (HHV) was determined on 30 chip samples,
collected randomly from 10 truck loads (Volpi 1992).
Calorimetric tests were conducted with an adiabathic
calorimeter (Parr, model 6200) (Canagaratna and
Witt 1988). A Kruskal Wallis test suggested limited
variability (KW 0.679, p-value 0.712). The average
HHV of E. camaldulensis wood was 20.14 MJ kgd.w.–1.
Chipping delays had a very small incidence (9%),
much lower than reported in previous bibliography
(Spinelli and Visser 2009) (Fig. 2). Moving and po-
3. Results and discussion – Rezultati
i rasprava
Harvester delays represented 18.1% of the total
work time, and in line with the values reported by
Spinelli and Visser (2008) for short-rotation plantations (Fig. 1). Harvester delays were mostly due to
the need for sharpening the cutting chain; this is
explicable considering the type of wood harvested.
18
Fig. 1 Harvesting and bunching time analysis, percent incidence of time
elements
Slika 1. Analiza utro{aka vremena sje~e i uhrpavanja, postotni udjeli
trajanja sastavnica rada
Croat. j. for. eng. 33(2012)1
Mechanized Harvesting of Eucalypt Coppice for Biomass Production ... (15–24)
Fig. 2 Chipping time analysis, percent incidence of time elements
Slika 2. Analiza utro{aka vremena iveranja, postotni udjeli trajanja
radnih sastavnica
sitioning also had a very low incidence, due to the
good trafficability of the test area (Fig. 1 and 2).
Productivity (PSH15 and PSH0) of each working
phase was good (Table 3). As compared to literature
data of felling and bunching operations, it had a
higher productivity than a harvester used for felling
and processing (Spinelli et al. 2002a), but it had a
lower productivity and a higher cost than a proper
feller-buncher (Spinelli et al. 2002b). The average
gross time only for felling and bunching (average
stump fresh mass 0.33 tons) was 1.25 minutes, corresponding to a PSH15 per worker of 15.8 fresh t h–1.
R. Picchio et al.
For the regression analysis between dependent variable »gross time (T [min]) for felling and bunching«
and independent variable »stump fresh mass (x [t])«
110 stumps were sampled randomly among all the
data observed. The regression was expressed by the
equation: T = 0.774 + 1.458 x; R2 = 0.678 (Fig. 3).
According the regression analysis (Table 4) the model is significant at p<0.001.
The elaboration of experimental data collected
for chipping, related to the load of 10 trailer trucks,
shows a very good productivity: PSH15 of 44.7 t h–1
and a very low level of delay (9.0%), as compared to
literature data (Spinelli and Visser 2009, Spinelli and
Hartsough 2001). This is mainly due to the good
shape of trees and to a good yard organization, but
also to the fact that Spinelli and Visser (2009) and
Spinelli and Hartsough (2001) included all delay
events, including those with the duration longer than
15 minutes.
The average calculated height of felled stumps
was 11.4 ± 3 cm (p<0.05), a value that indicates the
need of lowering the stumps by chainsaw after
mechanical harvesting. This is very important for
the coppice wood or plantation physiology.
Fig. 4 shows the results of financial calculations.
The total production cost was 44.30 € t–1, broken
down as follows: 14.42 € t–1 for felling, bunching and
chipping; 12.83 € t–1 for chip transportation (performed with truck and trailer units, over a distance
of about 150 km); 2.05 € t–1 for the relocation and
Table 3 Productivity of felling-bunching (the work of loader included)
and chipping
Tablica 3. Proizvodnost sje~e i uhrpavanja (uklju~en rad utovariva~a)
te iveranja
Operation
Felling and
bunching
Sje~a i
uhrpavanje
Chipping
Iveranje
Total of the
yard
Ukupno na
radili{tu
PSH15
PSH0
PSH15
PSH0
t h–1worker–1 t h–1worker–1 m3 h–1worker–1 m3 h–1worker–1
15.8
19.3
13.9
17.1
44.7
49.1
39.6
43.5
11.7
13.9
Croat. j. for. eng. 33(2012)1
10.3
12.3
Fig. 3 Variation of gross time only for felling and bunching as a function
of the stump fresh mass (from the regression analysis in Tab. 4)
Slika 3. Odstupanja ukupnih vremena rada pri sje~i i uhrpavanju kao
funkcija mase panja u svje`em stanju (iz regresijske analize u tablici 4)
19
R. Picchio et al.
Mechanized Harvesting of Eucalypt Coppice for Biomass Production ... (15–24)
Table 4 Regression analysis of felling and bunching time predicted for stump fresh mass
Tablica 4. Regresijska analiza utro{aka vremena sje~e i uhrpavanja predvi|anih na osnovi mase svje`ega panja
Dependent variable
Zavisna varijabla
min cycle–1
Independent variables
Nezavisne varijable
Variable
Varijabla
Stump fresh mass
Masa svje`ega panja
Intercept
Ordinata
0.678
Count
Zbroj
108
F-Value
F-vrijednost
227.76
p-Value
p-vrijednost
<0.0001
Unit
Jedinica
Parameter
Parametar
Std. Error
Stand. pogre{ka
p-Value
p-vrijednost
t
1.458
0.0966
<0.0001
0.774
0.0584
<0.0001
R2
transfer of machines; 15 € t–1 for the stumpage (compensation to the forest owner). In this case, the relocation unitary cost was calculated dividing the
total cost sustained (2,000 €) for the total surface
worked by the yard (5 ha), and the result obtained
was divided for the tons of fresh biomass harvested
per hectare (195 t). The resulting profit for the enterprise is 5.70 € t–1.
The human energy consumption was estimated
on the basis of a human heart-rate response during
field work. The heart rate was recorded on five work
days and the ANOVA test showed no significant differences between the two workers (p<0.05) and between the different operations (p<0.01), and the average value was 87.2 bt min–1 ± 1.3. The calculated ener-
gy expenditure of working was 0.026 MJ min–1 per
worker. This value is significantly lower than that
reported in other studies (Christie 2008, Picchio et al.
2009, Scott and Christie 2004), but it is clearly explained by the high mechanization used in this yard.
Concerning energy inputs, a comparison was conducted between the results of this study and those of
similar studies, where the same mechanization level
was applied, and in this case it showed similar results
(cf. Yoshioka et al. 2005). However, the comparison
conducted between the results of this study and others in similar studies, where intermediate mechanization level was applied (Baldini et al. 2007), showed
different results. The input for mechanized harvesting was 0.8 GJ td.w.–1 (Table 5) vs. 1.5 GJ td.w.–1 for
Fig. 4 Financial budget of the mechanized forest yard
Slika 4. Financijski prora~un mehanizacije radili{ta
20
Croat. j. for. eng. 33(2012)1
Mechanized Harvesting of Eucalypt Coppice for Biomass Production ... (15–24)
Also due to the large amount of biomass harvested, the average output/input ratio was twice as high
as the literature data (8.6–11.7, Baldini et al. 2007)
available for the harvesting of eucalypt plantations,
with intermediate mechanization. Higher values
(36–48, Picchio et al. 2009) were also reported, but
they were obtained in other forest types (Quercus
cerris L. coppice).
The percentage energy efficiency (i.e 100*(output
– input)/output) was high and on average 95.8% ±
0.3. This value was similar to those reported in other
studies (about 91% Baldini et al. 2007, about 97%
Picchio et al. 2009).
Table 5 Total energy value of outputs and inputs (GJ ha–1) for all work
steps, transport included
Tablica 5. Ukupna vrijednost izlazne i ulazne energije (GJ ha–1) za sve
sastavnice rada s uklju~enim transportom
Output
Machines & Tool Input
Human Input
Total Input
Izlaz
Ulaz strojeva i alata
Ulaz radnika
Ukupni ulaz
0.2
108.1
Direct
Indirect
Neposredni
Posredni
95.2
12.7
2,565.8
R. Picchio et al.
4. Conclusions – Zaklju~ci
Mechanized harvesting allowed a substantial increase of the operational productivity recorded for
any single work step: felling/bunching, extraction
and chipping. Comparison with other two felling
studies (Baldini et al. 2007, Martins et al. 2009) reflecting different mechanization levels with escalating investment requirements, confirmed the excellent performance of the harvester John Deere 1270,
with a JD 762 C harvester head. However, it had a
lower productivity and a higher cost than a proper
feller-buncher (Spinelli et al. 2002b) but the harvester
was a machine more multipurpose and versatile,
and therefore preferred by Italian forestry companies that work in different agroforestry systems.
Mechanization resulted in a dramatic reduction
of felling costs: moreover, it strongly enhanced operator comfort and safety (Bell 2002).
In this kind of plantations, mechanization is most
appropriate, as demonstrated by high productivity
recorded in our study (PSH15 6.5 td.w. h–1worker–1)
and by the very favorable energy balance (output/
input 23.8 and 95.8% system efficiency). These performances far exceed those reported for intermediate
mechanization, still very popular in Italy. However,
harvesting cost is still high (44.30 € tf.w.–1, Fig. 4) and
could be reduced only through careful work planning.
The cost of harvesting (6.76 € t–1) would certainly
have been lower if it was a proper feller-buncher; the
machine has a lower hourly rate and can ensure higher productivity. The unusual use of harvester was
Fig. 5 Percent incidence of work steps on total energy use
Slika 5. Postotni udjeli radnih zahvata u ukupnoj energetskoj potro{nji
intermediate mechanization. This obviously affects
the energy balance (output/input ratio), which is
23.8 for mechanized harvesting and 12.9 for intermediate mechanization. The calculated detail data of
energy indirect input requirements for machinery
were: harvester 2.37 GJ ha–1 (19%); loader 1.28 GJ ha–1
(10%); forwarder with chipper 2.11 GJ ha–1 (17%);
truck with trail 6.94 GJ ha–1 (54%).
Fig. 5 shows the incidence of single work phases
on total energy input. Truck transport had the highest incidence (45% or 379 MJ td.w.–1), as also found in
other studies (Baldini et al. 2007, Picchio et al. 2009),
than chipping (33% or 283 MJ td.w.–1) and finally
felling and bunching (22% or 185 MJ td.w.–1).
Table 6 Energy efficiency, labor use and operational productivity (PSH15 e PSH0)
Tablica 6. Energetska u~inkovitost, korisnost rada i operativna proizvodnost (PSH15 e PSH0)
Output/Input
Izlaz/ulaz
23.8
System efficiency
Man work time
U~inkovitost sustava Vrijeme rada radnika
%
min td.w.–1
95.8
23.12
Croat. j. for. eng. 33(2012)1
PSH15
PSH15
PSH0
PSH0
td.w. h–1 worker–1
6.5
m3 h–1 worker–1
10.3
td.w. h–1 worker–1
7.6
m3 h–1 worker–1
12.3
21
R. Picchio et al.
Mechanized Harvesting of Eucalypt Coppice for Biomass Production ... (15–24)
determined by the fact that the dedicated CTL machine was nearby for the poplar plantation logging.
Furthermore, Italian forestry is still confronted with
a lack of trained forest workers, which may slow
down the transition towards mechanized harvesting.
As confirmed by many previous studies (e.g. Baldini et al. 2007, Picchio et al. 2009), this study also
shows the urgent need to minimize the costs and
energy inputs related to transportation, which can
be obtained by developing local markets for energy
biomass, thus reducing transportation distance. The
cost of chipping was particularly low, due to the
power of the machine used and the efficient work
system adopted. Field chipping excludes the extraction operation, which often results in long waiting
delays for the chipper.
The damages to soil and topsoil have not been
discussed in this study. The surveys and studies
about this yard are still running and they will be the
subject of a forthcoming work. In fact, as mentioned
by other authors (Picchio et al. 2011), the research on
damage caused by forest operations to the remaining trees and/or to the regeneration in forest stands
started at the beginning of the twentieth century and
its importance has been rising with the increasing
use of mechanized wood harvesting.
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(LCI) analysis. Journal of Forest Research 10(2): 125–134.
doi: 10.1007/s10310-004-0126-7.
Sa`etak
Visoko mehanizirano pridobivanje {umske biomase iz eukaliptusovih panja~a
Glavni su ciljevi ove studije bili utvr|ivanje proizvodnosti, isplativosti i energetske bilance (izlaz/ulaz) strojne
sje~e primijenjene na eukaliptusovim planta`ama u sredi{njoj Italiji. Da bi se procijenila energetska bilanca,
odre|eni su: posredni ulazi, tj. energija kori{tena za proizvodnju; neposredni ulazi, tj. potro{nja goriva, maziva i
potro{nja energije radnika tijekom posla; izlaz, tj. energetska vrijednost ukupno proizvedenoga drva. Povr{ine pod
eukaliptusovim planta`ama danas po procjenama zauzimaju oko 72 000 hektara (54 000 ha ~iste, a 18 000 ha
mje{ovite sastojine). Istra`ivano je u okolici Rima, na nadmorskoj visini od 35 m, u ravni~nom predjelu (prosje~an
je nagib terena 3 %). Sastojina je bila panja~a eukaliptusa (Eukaliptus camaldulensis Dehnh.) posje~ena prvi
put 2000. godine. Prostorni je raspored panjeva bio kvadrati~an s 3 m izme|u panjeva (1111 panjeva po hektaru).
Od 2009. napadi kukaca (Phorachantha semipunctata) smanjili su gusto}u panjeva na 592 panja po hektaru.
Zna~ajke gospodarenja eukaliptusovim planta`ama u Italiji su:
Þ povratak autohtonoj {umskoj vegetaciji na podru~jima pod nisko proizvodnim planta`ama, posebno u
ju`noj Italiji
Þ pobolj{anje sastojina industrijskih planta`a radi pove}anja kakvo}e i koli~ine proizvodnje (sastojine srednjih i kratkih ophodnji namijenjenih proizvodnji drvnoga iverja); navedeno se namjerava posti}i selekcijom
klonova
Þ racionalizirana uporaba proizvoda u tzv. poljskom {umarstvu (eng. agroforestry), gdje planta`e mogu proizvoditi i tehni~ke drvne sortimente, ogrjevno drvo i drvni iver.
Primijenjena je stablovna metoda izradbe i krajnji je proizvod bio drvni iver za energiju. Nasadi za proizvodnju
energije dobar su izbor pri osiguravanju sirovine za bioenergane. Isplativost energetskih nasada uvelike je ovisna o
odgovaraju}oj logistici, planiranju proizvodnje i prinosa. Tro{kovi strojnoga rada bili su izra~unati pomo}u koeficijenata i matemati~kih formula preuzetih iz vode}ih metodologija koje su predlo`ili razni autori. Ti su podaci bili
upotrijebljeni za odre|ivanje ekonomske i energetske odr`ivosti strojne sje~e. Pro{lih godina mehanizacija se brzo
uvodila u {umske operacije. Pravilna je izobrazba radnika i planskoga osoblja nu`na, posebno kada se uvodi strojna
sje~a za odr`ivo kori{tenje {umske biomase kao obnovljivoga izvora energije uz smanjivanje emisije stakleni~kih
plinova. Energetska je bilanca bila procijenjena metodom GER (eng. Gross Energy Requirements). Metoda GER
tako|er je primijenjena za procjenu neposrednih i posrednih inputa za uoptrijebljene strojeve. Nadalje, kod posredne
metode procjene utro{aka energije u {umarskim operacijama u sastojini bila je procijenjena potro{nja energije radnika
Croat. j. for. eng. 33(2012)1
23
R. Picchio et al.
Mechanized Harvesting of Eucalypt Coppice for Biomass Production ... (15–24)
prema otkucajima srca tijekom rada. Dva su radnika bila pra}ena svakoga radnoga dana. Pri dolasku na posao
odabrani su radnici bili opremljeni s Polarovim mjera~em otkucaja srca. Za izra~un izlazne energije ve}a ogrjevna
vrijednost (HHV) bila je odre|ena na 30 uzoraka drvnoga iverja, koje se skupljalo nasumi~no s 10 kamionskih tovara.
Kalorimetri~ni su testovi bili izvedeni s adijabatskim kalorimetrom (Parr, model 6200). Prosje~na vi{a ogrjevna
vrijednost eukaliptusa bila je 20,14 MJ kgd.w.–1. Tijekom radnoga vremena prekidi rada harvestera bili su 18,1 %
ukupnoga radnoga vremena, prekidi rada pri iveranju zauzimali su manje vrijednosti (9 %), kao i premje{tanje i
zauzimanje polo`aja zbog dobre kretnosti na istra`ivanom podru~ju. U tim je planta`ama strojna sje~a omogu}ila
bitno pove}anje operativne proizvodnosti zabilje`ene za svaku sastavnicu radnoga procesa: ru{enje/uhrpavanje,
izvo`enje i iveranje, {to je pokazano visokom zabilje`enom proizvodno{}u (PSH15 = 6,5 td.w.h–1radnik–1) i povoljnom
energetskom bilancom (izlaz/ulaz = 23,8; 95,8 % u~inkovitosti sustava). Takva djelotvornost prema{uje onu
zabilje`enu kod sustava ni`e razine mehaniziranosti koji su i dalje vrlo popularni u Italiji. Cijena sje~e (6,76 € t–1)
svakako bi bila ni`a u slu~aju da je kori{ten feler ban~er (eng. feller buncher) koji ima ni`e tro{kove po satu rada i koji
mo`e osigurati vi{u proizvodnost. Neobi~na uporaba harvestera u tom slu~aju bila je odre|ena ~injenicom da je stroj
bio u blizini i da je radio na pridobivanju drva iz topolovih planta`a. U svakom je slu~aju cijena sje~e visoka (44,30 €
TF.w.–1) i mo`e se smanjiti samo pa`ljivim operativnim planiranjem. Prosje~na je visina panjeva bila 11,4 ± 3 cm (p<
0,05), odnosno to je vrijednost koja upu}uje na potrebu dodatnoga skra}ivanja panjeva uporabom motorne pile
lan~anice nakon strojne sje~e. To je vrlo va`no za fiziologiju panja~a ili planta`a. Tro{ak je iveranja bio iznimno nizak
zbog velike snage kori{tenoga stroja i u~inkovitoga sustava rada. Iveranje u sastojini isklju~uje privla~enje drva, {to
~esto rezultira du`im zastojima pri radu ivera~a. [tete na tlu i na povr{inskom sloju tla nisu detaljno analizirane u
ovom radu. Istra`ivanje i prou~avanje toga radili{ta i dalje je u tijeku te }e biti predmet budu}ih analiza.
Klju~ne rije~i: harvester, proizvodnost rada, operativni tro{kovi, energetska bilanca, ivera~, forvarder, {umske
planta`e
Authors’ addresses – Adrese autorâ:
Rodolfo Picchio, PhD
e-mail: r.picchio@unitus.it
Alessandro Sirna, MSc.
e-mail: sandrosirna@unitus.it
Raffaello Spina, MSc.
e-mail: rspina@unitus.it
Department of Science and Technology for
Agriculture, Forests, Nature and Energy
(DAFNE)
University of Tuscia
Via San Camillo de Lellis, 01100 Viterbo
ITALY
Giulio Sperandio, MSc.
e-mail: giulio.sperandio@entecra.it
Agricultural Research Council (CRA)
Research Unit for Agricultural Engineering
Via della Pascolare, 16, 00016 Monterotondo
(Roma)
ITALY
Received (Primljeno): November 29, 2010
Accepted (Prihva}eno): November 21, 2011
24
Stefano Verani, MSc.
e-mail: stefano.verani@entecra.it
Agricultural Research Council (CRA),
Research Unit for Wood Production Outside
Forests
Periferic Operative Structure of Roma
Via Valle della Questione, 27, 00166 Roma
ITALY
Croat. j. for. eng. 33(2012)1
Original scientific paper – Izvorni znanstveni rad
Productivity and Profitability of Forest
Machines in the Harvesting of Normal and
Overgrown Willow Plantations
Fulvio Di Fulvio, Dan Bergström, Kalvis Kons, Tomas Nordfjell
Abstract – Nacrtak
Forage harvesters used in Short Rotation Willow Coppice (SRWC) plantations in Sweden
suffer from an inability to efficiently harvest stems thicker than 6 – 7 cm at stump height. An
alternative, when harvesting in such plantations, might be to use forest machines fitted with
accumulating felling heads. This study aimed to measure the time consumption and to
compare the costs of two forest machine systems in a normal (N) and an overgrown (O)
SRWC, where the respective biomass densities were 36 and 56 Oven-Dry tonnes (OD t) per
ha. The first machine system included a harvester and a forwarder and the second consisted of
a harwarder (one-machine system). When harvesting and forwarding the biomass for 250 m,
the productivity of the two and one-machine system was on average 2.3 (sd = 0.6) and 0.9
(sd = 0.2) OD t/Productive Work hour, respectively. Biomass density or stem sizes had a marginal effect on the time consumption per hectare for the two-machine system, but were significant for the one-machine system. The productivity for the two-machine and one-machine
system in the O area, compared to the N area, was 40% and 36% higher, respectively. The net
income was positive when using the harvester–forwarder system but it was negative for the
harwarder. Increases in biomass density or stem sizes increased the profitability of the machine
systems studied. Thus, if dealing with more overgrown plantations than those studied, forest
machines, and especially a harvester-forwarder system, may offer an efficient and economical
alternative to conventional forage harvesters.
Keywords: System analysis, time study, productivity, harvester, forwarder, harwarder
1. Introduction – Uvod
Current field design of Short Rotation Willow
Coppice (SRWC) plantations for energy has increased the efficiency of cultural operations, allowing for
fully-mechanized cultivation and harvesting (Mola-Yudego 2011, Mitchell et al. 1999). The harvesting
operation accounts for about half the total cost of
SRWC production; the remainder of the cost is attributable to cultivation (25%) and biomass transportation (25%) (Sims 2002). Nearly all SRWC in Sweden
are harvested by direct chipping, using forage harvesters equipped with wood cutting headers and
shuttles for transporting the chipped biomass to the
road side (Nordh and Dimitriou 2003). The forage
harvesters tend to have problems with stems and
therefore the diameter at stump height (dsh) (i.e. the
cutting height) exceeds 6 – 7 cm. For instance, as
Croat. j. for. eng. 33(2012)1
such thick stems are relatively inflexible, they are not
readily bent to fit into and pass through the feeding
and cutting unit (Nordh and Dimitriou 2003). Spinelli et al. (2008) found that when the average dsh
exceeded ca. 4 cm, the mechanical stress on the machines increased and in turn reduced the machines’
work availability from 94% to 84% (Spinelli et al. 2008).
It is to be expected that future SRWC plantations will
achieve higher biomass yields due to the breeding of
new and better clones (Mola-Yudego 2011). As such,
it is likely that the average dsh of the harvested trees
will increase, requiring harvesters that can handle
larger stems (Nordh and Dimitriou 2003). In fact,
such a need already exists to some extent: the use of
conventional forage harvesters can be challenging
when harvesting SRWC that has become somewhat
overgrown (i.e. which contains a notable amount of
stems larger than 4 cm in dsh) (Magnusson 2009).
25
Fulvio Di Fulvio et al.
Productivity and Profitability of Forest Machines in the Harvesting ... (25–37)
One possible way to work around these problems
would be to use forest machines developed for harvesting small trees for bioenergy in first thinnings.
Such forest machine systems are highly reliable and
can handle stems/trees much larger than those found
in overgrown SRWC plantations. In the Nordic countries, two-machine systems consisting of a harvester
equipped with an accumulating felling head (AFH)
and a forwarder that transports the biomass to the
roadside are commonly used for such operations.
However, one-machine systems are also used consisting of a machine (a harwarder) that both fells and
transports the biomass to the roadside (cf. Talbot et
al. 2003).
A detailed understanding of the factors affecting
the productivity and operating costs of forest machines when used in SRWC plantations could facilitate the development of approaches that would
make their use more profitable than that of conventional forage harvesting systems when harvesting
significantly overgrown SWRC plantations.
Therefore the aim of this study was:
Þ to study the effect of work methods and biomass
density (normal and overgrown) on the work time
consumption of a harvester–forwarder system
and a harwarder system in willow plantations,
Þ to compare their productivity, costs and profitability.
2. Material and Methods – Materijal
i metode
The study site was located in Ransta, Sweden
(59°49'N, 16°38'E). A Salix viminalis L. clone »Tora«
plantation was established there in the year 2000 in a
double row pattern (Fig. 2). The plantation was intended to be harvested every five years on a regular
basis. At the time the study was conducted, it had
been grown by six years since it had last been harvested. The plantation covered an area of 17.2 ha, of
which 3.6 ha were used for the study. The study was
conducted in 2010, between the 29th of November
and the 9th of December. The ground surface was
partially frozen and covered with a snow layer to a
depth of ca. 5 cm and had a high bearing capacity.
The study area was inventoried in rectangular plots
with a width of 5 single rows (5 m) and a length of 4
stools (2.4 m) (i.e. a stool is a stump from which
stems sprout), giving a sample area of 12 m2. The
plots were regularly distributed in the direction of
the rows and separated from one another by 10 m,
giving a density of 80 plots per hectare. The study
area contained both normal (N) and overgrown (O)
areas (Table 1). The biomasses were estimated by
26
Table 1 Average values for the properties of the two study areas.
Standard deviations are quoted in parentheses. OD = oven-dry
Tablica 1. Prosje~ne vrijednosti zna~ajki dvaju istra`ivanih podru~ja.
Standardna je devijacija navedena u zagradama. OD = suha tvar
Properties – Svojstva
Density, stool/ha – Gusto}a, panj/ha
Density, stems/stool
Gusto}a, stabljika/ha
Diameter at stump height, cm*
Promjer na panja, cm*
Height, m* – Visina, m*
Biomass, OD t/ha – Biomasa, OD t/ha
Biomass, raw mass, t/ha
Biomasa, sirova masa, t/ha
Mean annual increment, OD t/ha, year
Srednji godi{nji prirast, OD t/ha, godina
Study areas
Istra`ivano podru~je
Normal
Overgrown
Normalno
Preraslo
13,815 (1,527) 12,765 (2,859)
3.5 (0.5)
3.7 (0.7)
2.7 (1.2)
3.1 (1.5)
5.4 (2.1)
36 (8)
6.0 (2.2)
56 (17)
72 (16)
114 (35)
6.0
9.3
*Arithmetic mean value – Aritmeti~ka srednja vrijednost
sampling 35 stems representing the full range of observed dsh; their dsh, height and fresh weight were
measured. A sub sample of stems was then chopped
into ca. 0.2 liters small pieces and their moisture
content (MC, wet basis) was determined according
to CEN/TS 14774-2 (2004). The MC was on average
50.4% (sd 1.6%). The oven-dry (OD) masses of stems
with different dsh were then used to generate a
biomass function [1] (cf. Verwijst and Telenius 1999):
Stem mass (OD kg) = 0.0001 ´ dsh2.603; R2 = 0.979 (1)
Where:
dsh diameter at stump height, mm
A harvester and forwarder system and a harwarder
system were studied. The harvester was a Valmet
911.1 (Komatsu Forest AB, Sweden) with 4 wheels, a
mass of 15.2 t, a power output of 129 kW and a width
of 2.7 m. The harvester crane was a Cranab CRH 16
(Cranab AB, Sweden) with a maximum reach of 9.8 m
and equipped with the Bracke C16.a (Bracke Forest
AB, Sweden) AFH with a mass of 500 kg which cuts
trees with a saw-chain attached to a rotating disc
with a diameter of 795 mm. The forwarder was a
Timberjack 1210B Pendo (John Deere Forestry Oy,
Finland) with 8 wheels, a mass of 15.5 t, a power
output of 114 kW and a width of 2.8 m. The load
capacity of the machine was 14 t and the load bunk
cross sectional area was 4.2 m2. The forwarder crane
was a Loglift F71 FT (Loglift Jonsered AB, Sweden)
with a maximum reach of 10.0 m. The forwarder was
Croat. j. for. eng. 33(2012)1
Productivity and Profitability of Forest Machines in the Harvesting ... (25–37)
Fulvio Di Fulvio et al.
Fig. 1 The number of stems (bars) and the biomass (polygons) per ha as a function of stem diameter at stump height for the normal (N) and overgrown (O)
areas. Dsh = diameter at stump height, OD = oven-dry
Slika 1. Broj stabljika (stupci) i biomasa (poligoni) po hektaru kao funkcija promjera stabala na visini panja za normalno (N) i preraslo (O) podru~je. Dsh
= promjer na visini panja, OD = suha tvar
equipped with a slash grapple (Hultdins AB, Sweden)
with a grapple-area of 0.36 m2. The same forwarder
was also used as a harwarder, and in this case it was
equipped with the Naarva Grip 1500-25 E (Pentin
Paja Oy, Finland) accumulating felling-grapple. During the experiments the harvester, forwarder and
harwarder were operated by one, two and one operator, respectively. All operators were professionals
and experienced with harvesting of small trees in
thinning operations.
The harvester felling and bunching work was
studied as a function of 3 factors, giving 8 different
treatment combinations: factor a, biomass density
(N and O); factor b, number of harvested double-rows (5 and 6 rows); and factor g, working method
(i.e. front and side to side; see Fig. 2 for an explanation of these terms). The cut stems were bunched
in piles positioned to the rear of the machine, at an
angle of ca. 45° to the strip road, on the side of the
harvester with the butt ends pointing towards the
machine (Fig. 2). For each treatment combination the
harvester’s operation was studied for at least 0.5
Productive Work hours (PW) hours (IUFRO 1995)
and for at most 1 PW-hour, short delays were also
recorded. A randomized block design with 3 blocks
was used; in total, 24 study units were harvested in
the experiment (12 in N and 12 in O) (Fig. 3). The
results of the experiment were analyzed by ANOVA,
using a general linear model of the form:
Croat. j. for. eng. 33(2012)1
yijkl = m + ai + bj + gk + c1 + ai ´ bk + ai ´ gk +
bj ´ gk + ai ´ bj ´ gk + eijkl
(2)
Where:
m
a
b
g
e
overall mean,
biomass density,
number of harvested double-rows,
working method,
error.
The forwarder loaded the piles into the bunk area
until a full load was achieved (up to the full length of
the stakes) and then hauled the biomass to roadside,
where the stems were unloaded perpendicular to the
direction of the road, with their butt ends pointing
towards the road. The forwarder’s work time consumption was analyzed in terms of the factors a and
b (see above) using a linear ANOVA model of the
form:
yijk = m + ai + bj + ck + ai ´ bj + eijk
(3)
The harwarder cut and directly loaded the stems
until the bunk area was loaded to the capacity and
then hauled the biomass to the roadside for unloading (Fig. 4). Each load corresponded to a study unit.
Six study units (three blocks) were harvested in the
O area and two in the N area (one block) (Fig. 3). The
results of the work in the O stand were analyzed
using a two-way ANOVA model:
27
Fulvio Di Fulvio et al.
yij = m + ti + bj + eij
Where:
m
overall mean,
ti
treatment main effect
(number of harvested rows),
Productivity and Profitability of Forest Machines in the Harvesting ... (25–37)
(4)
bj
eij
block main effect,
random error term.
The average work time consumption in the O
area (six study units) was compared to the average
work time consumption in the N area (two study
Fig. 2 The working methods used with the harvester when harvesting either 5(a) or 6(b) double-rows, in a direction parallel (a.1 and b.1) or perpendicular
(a.2. and b.2) to the orientation of the machine. The large hollow arrows on the right hand side of the drawings indicate the machine’s working direction.
The alphabetic sequence of capital letters in each drawing shows the sequence of crane cycles (i.e. the stools in the area marked »A« were felled first, then
those in the area marked »B«, etc.) The small black arrows in the drawings indicate the direction of the crane’s movement during felling and bunching; the
shaded oval regions denote approximately the area felled during each crane cycle
Slika 2. Metode rada primijenjene pri radu harvestera kod sje~e 5(a) ili 6(b) duplih redova, u paralelnom ili okomitom smjeru u odnosu na orijentaciju
stroja. Velike prazne strelice na desnoj strani crte`a prikazuju radni smjer stroja. Abecedni slijed velikih slova na svakom crte`u prikazuje slijed ciklusa
krana (panjevi na povr{ini A sje~eni su prvi, zatim oni na povr{ini B itd.). Male crne strelice na crte`u pokazuju smjer kretanja krana tijekom sje~e i vezanja
snopova; zasjen~ena ovalna podru~ja prikazuju pribli`no povr{ine koje su sje~ene u svakom ciklusu krana
28
Croat. j. for. eng. 33(2012)1
Productivity and Profitability of Forest Machines in the Harvesting ... (25–37)
Fig.3 The spatial layout of the study units (cells), with their treatments, in
the study area. The italic letter in each of the cells indicates the block
affiliation (i.e. »a, b, c« for the harvester–forwarder and »d, e, f, g« for
the harwarder). The capital letters indicate the biomass density (i.e.
normal (N) and overgrown (O)). Numbers indicate the number of
harvested double-rows (i.e. 5 and 6 rows and 2 and 3 rows). The letter
positioned after the numbers indicates the harvester’s working method
(i.e. in front (f) and side to side (s))
Slika 3. Prostorni raspored istra`ivanih jedinica (polja), s njihovim
postupcima, u istra`ivanom podru~ju. Kurzivno slovo u svakom polju
prikazuje pripadnost bloka (npr. »a, b, c« za forvarder–harvester i »d, e,
f, g« za harvarder). Velika slova pokazuju gusto}u biomase (npr.
normalno (N) i preraslo (O)). Brojevi pokazuju broj posje~enih duplih
redova (npr. 5. i 6. red te 2. i 3. red). Slova iza brojeva pokazuju radnu
metodu harvestera (npr. ispred (f) i sa strane na stranu (s))
units). The data were analysed using Tukey's t-test;
differences were considered significant if p < 0.05.
The work time consumption was recorded by
using the Allegro Field PC® and the SDI software
Fulvio Di Fulvio et al.
(Haglöf, AB). The individual work elements involved
in the operation of the harvester took relatively short
time and where therefore studied with frequency
measurements (cf. Harstela 1991). The harvester’s
operational state (i.e. the work element currently in
progress) was recorded once every 7 s, giving precedence to the element with the highest priority as
specified in Table 2. In addition, the total time consumption was recorded in order to control for missed observations.
The individual work elements in the operation of
the forwarder and harwarder took a relatively long
time and they were therefore studied with snap-back
timing (continuous time recording) rather than frequency registration (cf. Harstela 1991). The times
were recorded in cmin (i.e. 1 cmin = 1/100 min). The
work time was recorded separately for the various
work elements listed in Table 3.
The harvested area was subsequently inventoried in 28 rectangular sample plots (sized to contain 20
stools) and systematically laid out and spaced 30 m
along the strip roads. In each plot, the cutting height
of each stool was measured, the number of damaged
stumps was counted and the depth of the tire tracks
(i.e. the distance between the bottom and the rim
edge for each track section) in relation to the midsection of each sample plot was measured. A stump
was considered to be damaged if more than half of
its radius was cracked.
Fig. 4 The working methods used with the harwarder when harvesting either 3 (c.1) or 2 (c.2) double-rows. The large hollow arrows on the right hand side
of the drawings indicate the machine’s working direction. The alphabetic sequence of capital letters in each drawing shows the sequence of crane cycles
(i.e. stools in the area marked »A« were felled first, then those in the area marked »B«, etc.). The small black arrows indicate the direction of the crane’s
movement during felling and bunching; the shaded oval regions denote approximately the area felled during each crane cycle
Slika 4. Metode primijenjene pri radu harvardera kod sje~e 3 (c.1) ili 2 (c.2) duplih redova. Velike prazne strelice na desnoj strani crte`a prikazuju radni
smjer stroja. Abecedni slijed velikih slova na svakom crte`u prikazuje slijed ciklusa krana (panjevi na povr{ini A sje~eni su prvi, zatim oni na povr{ini B itd.).
Male crne strelice na crte`u pokazuju smjer kretanja krana tijekom sje~e i vezanja snopova; zasjen~ena ovalna podru~ja prikazuju pribli`no povr{ine koje
su sje~ene u svakom ciklusu krana
Croat. j. for. eng. 33(2012)1
29
Fulvio Di Fulvio et al.
Productivity and Profitability of Forest Machines in the Harvesting ... (25–37)
Table 2 Definitions of the work elements in the operation of the harvester
Tablica 2. Definicije radnih elemenata u radu harvestera
Work element
Radni element
Description
Opis
Priority*
Prioritet*
Boom out
Prazan kran
Starts when an empty crane moves towards the first stool to be harvested and stops when the first tree has been reached
Po~inje kada prazni kran kre}e prema prvomu panju gdje }e se sje}i i zavr{ava kada se dosegne prvo stablo
2
Felling and accumulating
Sje~a i kumuliranje
Starts when the first tree has been reached and stops when the last tree has been felled
Po~inje kada se dosegne prvo stablo i zavr{ava kada se zadnje stablo posije~e
1
Boom in
Puni kran
Starts when the last tree in the crane cycle has been felled and stops when trees have been dropped on the ground
(includes time spent arranging the bunch) – Po~inje kada je zadnje stablo u ciklusu krana posje~eno i zavr{ava kada su
stabla spu{tena na tlo (uklju~uje vrijeme ure|enja sve`nja)
2
Moving
Kretanje
Starts when the machine wheels begin turning and stops when the wheels stop
Po~inje kada se kota~i stroja po~inju okretati i zavr{ava kada se kota~i zaustave
3
Miscellaneous
Razno
Other activities e.g. cutting roots away from the bottom of the stems
Ostale aktivnosti, npr. rezanje korijena sa stabla
4
Delays
Zastoji
E.g. repairs and personal breaks
Npr. popravci i osobni odmori
4
*If work elements were performed simultaneously, the element with the highest priority (lowest number) was recorded
*Ako su radni elementi izvo|eni istodobno, element je s vi{im prioritetom (manji broj) zabilje`en
Table 3 Definitions of the work elements in the operation of the forwarder (F) and harwarder (H)
Tablica 3. Definicije radnih elemenata u radu forvardera (F) i harvardera (H)
Work element
Radni element
Boom out, H
Prazan kran, H
Description
Opis
Priority*
Prioritet*
Starts when an empty crane moves towards the first stool to be harvested and stops when the first tree has been reached
Po~inje kada prazni kran kre}e prema prvom panju gdje }e se sje}i i zavr{ava kada se dosegne prvo stablo
1
Felling and accumulating, H Starts when the first tree has been reached and stops when the last tree has been felled
Sje~a i kumuliranje, H
Po~inje kada se dosegne prvo stablo i zavr{ava kada se zadnje stablo posije~e
1
Loading, H
Utovar, H
Starts immediately after the felling of the last tree in the crane cycle and stops when the bunch of trees has been
transferred to the log bunk
Po~inje odmah nakon sje~e zadnjega stabla u ciklusu krana i zavr{ava kada je sve`anj stabala prenesen u utovarni prostor
1
Loading, F
Utovar, F
Starts when the empty crane move from its base position in the bunk area and stops when the crane returns to the load bunk
Po~inje kada prazan kran krene sa svoje osnovne pozicije u podru~ju le`i{ta i zavr{ava kada se vrati u utovarni prostor
1
Moving while loading, F–H Starts when the machine wheels begin turning and ends when the wheels stop moving to allow cutting/loading
Kretanje pri utovaru, F–H Po~inje kada se kota~i stroja po~inju okretati i zavr{ava kada se kota~i zaustave da omogu}e sje~u/utovar
2
Moving loaded, F–H
Puna vo`nja, F–H
Starts when the machine moves from the study unit and ends when the machine stops at the landing
Po~inje kada stroj kre}e s istra`ivane jedinice i zavr{ava kada se zaustavlja na stovari{tu
2
Unloading, F–H
Istovar, F–H
Starts when the machine stops at the landing and ends when the base machine starts to move from the landing
Po~inje kada se stroj zaustavi na stovari{tu i zavr{ava kada krene sa stovari{ta
1
Moving unloaded, F–H
Prazna vo`nja, F–H
Starts when the machine moves from the landing and ends when the machine stops at the cutting/loading area
Po~inje kada stroj kre}e sa stovari{ta i zavr{ava kada se zaustavlja na mjestu sje~e/utovara
2
Miscellaneous, F–H
Razno, F–H
Other activities, e.g. picking up dropped bunches, etc
Ostale aktivnosti, npr. podizanje ispalih sve`njeva
3
Delays, F–H
Zastoji, F–H
E.g. repairs and personal breaks
Npr. popravci i osobni odmori
3
*If work elements were performed simultaneously, the element with the highest priority (lowest number) was recorded
*Ako su radni elementi izvo|eni istodobno, element je s vi{im prioritetom (manji broj) zabilje`en
30
Croat. j. for. eng. 33(2012)1
Productivity and Profitability of Forest Machines in the Harvesting ... (25–37)
The system analysis boundaries were defined to
include harvesting and forwarding of the biomass
piled at roadside. The plantation size was set to 10 ha
(cf. Rosenqvist et al. 2000), giving a forwarding distance of 250 m. The analyses were based on the
average productivity of the harvester and harwarder
when harvesting six and three double rows, respectively. The conversion of PW into Work Time including delays shorter than 15 min (WT) (IUFRO 1995)
was based on the maximum proportion of delay
time recorded in the field study for each system. The
interest rate was set to 6% and the calculation was
made according to Harstela (1993). The purchase prices were set for the harvester, forwarder and harwarder to €285,000, €225,000 and €270,000, respectively
(cf. Laitila 2008). The annual utilization time (AU)
for the harvester, forwarder and harwarder were set
to 2,361 WT-hours/year, 2,500 WT-hours/year and
2,430 WT-hours/year, respectively (cf. Nurminen et
al. 2009). The AU for the harwarder was calculated
as an average of the harvester and forwarder values.
The economic lifetime was set to 6 years and the
salvage value was set to 20% of the purchase price.
The operator costs were set to 20 €/WT-hour. The
calculated hourly operating costs of the harvester,
forwarder and harwarder were 85.2 €/WT-hour,
70.4 €/WT-hour and 79.6 €/WT-hour, respectively.
The relocation cost was set to 200 € per machine and
relocation. The gross income was based on current
market price for un-comminuted tree parts delivered at road side of 21.0 €/m3solid (Anon 2010). A
conversion rate of 397 OD kg/m3solid was used (cf.
Nurmi 1995). The net income of the removal was
calculated as the difference between the roadside
gross income and the harvesting costs (including
relocation costs).
3. Results – Rezultati
The harvester was studied for 19.67 WT hours, of
which delay time accounted for 0.3%. The harvested
area was 1.46 ha. The PW time consumption per ha in
the N and O area was 13.2 (sd = 1.4) and 13.5 (sd = 1.2)
hours, respectively, which corresponds to respectively 0.36 and 0.24 PW-hours/OD t. The average productivity of the harvester was 3.5 OD t/PW-hour. The
biomass density (factor a) and the number of harvested rows (factor b) had significant effects on productivity (p < 0.001 and p = 0.036, respectively). Consequently, the productivity was 54.4% higher in the O
area than in N, and it was 9.3% higher when harvesting five rather than six rows. The working method
(factor g) had no significant effect on productivity (p =
0.132). No significant block or interaction effects on
PW time consumption per hectare were found.
Croat. j. for. eng. 33(2012)1
Fulvio Di Fulvio et al.
The average number of felled and accumulated
stools per crane cycle in the N and O areas was 13.2
and 8.8, respectively, and the difference was significant (p < 0.001). The average amount of biomass
harvested in a full crane cycle in the N and O areas
was 34.3 and 39.6 OD kg, respectively, and the difference was significant (p = 0.018). The total time consumption per stool did not differ significantly for
any of the eight examined combinations of the tree
factors (Table 4). However, the greater biomass density (factor a) in O areas (relative to N areas) resulted
in a 10.6% and significant increase (p = 0.019) in the
PW time consumption per stool. Harvesting five
rows instead of six (factor b) caused an 8.9% significant reduction (p = 0.029) in PW time per stool.
The forwarder was studied for 7.64 WT-hours, of
which delay time accounted for 8%. In total 25 full
loads were loaded, forwarded to roadside and un-loaded. At a hauling distance of 250 m, the time
required for forwarding averaged 21.8 PW-min per
load, which corresponds to a productivity of 7.2 OD
t/PW-hour. The corresponding PW time consumption per hectare in the N and O area is then 5.0 (0.5)
and 7.8 (0.7) hours, respectively. A full load averaged
2.6 OD t (5.3 fresh t), which corresponds to 38% of
the machine’s load capacity. The load size reached
2.5 and 2.7 OD t (4.8 and 5.7 fresh t), respectively, in
the N and O area, the difference in load size was not
significant (p = 0.100). To reach a full load in the N
and O area, in average 15 and 13 crane cycles were
required, respectively. The average forwarding distance was 163 m (min. 32 and max. 317 m). An average strip road length of 47 m was required to achieve
a full load. The forwarder’s average moving speed
during productive work was 1.2 m/s when unloaded and 1.0 m/s when loaded. The average calculated
bulk density of a full load was 109 OD kg/m3 (220
fresh kg/m3). Unloading took 4.66 PW-min per load
on average (1.79 PW-min/OD t) and required an
average of 10.8 crane cycles; the mass handled per
crane cycle was 0.25 OD t. Miscellaneous time accounted for 0.58 PW-min per load on average (0.22
PW-min/OD t). Loading and moving while loading
accounted for 7.39 and 1.36 PW-min per load (2.84
and 0.52 PW-min/OD t), respectively. The biomass
density and number of rows (factors a and b) did not
significantly affect the total time spent in loading
and moving while loading in terms of PW-time/OD t.
However, in the O area, the loading work element
took 18% longer than was the case in the N area, and
this difference was significant (p = 0.026) (Table 5).
The harwarder was studied for 15.09 WT-hours,
of which delay time accounted for 4%. It harvested
an area of 0.29 ha. In total, 8 full loads were produced. At a hauling distance of 250 m, the producti-
31
Fulvio Di Fulvio et al.
Productivity and Profitability of Forest Machines in the Harvesting ... (25–37)
Table 4 Productive work time (PW) consumed per stool (s/stool) during harvester operation
Tablica 4. Proizvodno radno vrijeme (PW) utro{eno po panju (s/panj) za vrijeme rada harvestera
Factor, a
Faktor, a
B
Normal, N
Normalno, N
5 rows – 5 redova
Overgrown, O
Preraslo, O
6 rows – 6 redova
5 rows – 5 redova
6 rows – 6 redova
Forward
Ispred
Side to side
Strana na stranu
Forward
Ispred
Side to side
Strana na stranu
Forward
Ispred
Side to side
Strana na stranu
Forward
Ispred
Side to side
Strana na stranu
n=3
n=3
n=3
n=3
n=3
n=3
n=3
n=3
Boom out
Prazan kran
0.304a
0.341a
0.341a
0.310a
0.434a
0.471a
0.461a
0.530a
Felling and accumulating
Sje~a i kumuliranje
2.415ab
2.241b
2.704ab
2.758ab
2.591ab
2.338b
2.907a
2.466ab
Boom in
Puni kran
0.461a
0.466a
0.521a
0.420a
0.593a
0.556a
0.621a
0.632a
Moving
Kretanje
0.120ab
0.120ab
0.080b
0.082b
0.121ab
0.179a
0.103b
0.096b
Miscellaneous
Razno
0.028a
0.000a
0.011a
0.022a
0.009a
0.017a
0.044a
0.035a
Total time
Ukupno vrijeme
3.327a
3.168a
3.657a
3.592a
3.747a
3.561a
4.135a
3.760a
G
Total PW time consumption per stool, p-values: Factor a = 0.019, Factor b = 0.029, Factor g = 0.176, Factor a × b = 0.769, Factor a × b = 0.551, Factor b × g = 0.866, Factor a × b × g
= 0.615, Block = 0.444
The p-values in bold indicate significant differences (p £ 0.05). Different superscript letters row-wise indicate significant (p £ 0.05) differences between treatments according to Tukey’s
simultaneously test of means
Ukupno PW utro{eno po panju, p-vrijednosti: faktor a = 0.019, faktor b = 0.029, faktor g = 0.176, faktor a × b = 0.769, faktor a × b = 0.551, faktor b × g = 0.866, faktor a × b × g =
0.615, blok= 0.444
p-vrijednosti ozna~ene poludebelo pokazuju zna~ajne razlike (p £ 0.05). Razli~ita slova u eksponentu po redovima pokazuju zna~ajne (p £ 0.05) razlike izme|u postupaka prema
Tukeyevu testu
Table 5 Productive work time (PW) consumed by individual work elements in the operation of the forwarder when loading and moving while loading. The
table shows the PW time consumed for different biomass densities (factor a, which can be either normal (N) or overgrown (O)) and the effects of
operational factors, including the biomass concentration along strip roads, pile size, number of piles per crane cycle, and machine position. Standard
deviations are given within brackets
Tablica 5. Proizvodno radno vrijeme (PW) utro{eno po pojedinim radnim elementima u radu forvardera kod utovara i kretanja pri utovaru. Tablica
pokazuje PW utro{eno za razli~ite gusto}e biomase (faktor a, koji mo`e biti ili normalno (N) ili preraslo (O)) i utjecaje radnih ~imbenika uklju~uju}i
koncentraciju biomase pored putova, veli~inu slo`aja, broj slo`aja po ciklusu krana i poziciju stroja. Standardne su devijacije dane u zagradama
Factor a – Faktor a
Normal, N – Normalno, N
Overgrown, O – Preraslo, O
n = 12
n = 12
min/OD t
%
min/OD t
%
2.61 (0.46)
a
Moving while loading – Kretanje pri utovaru
0.54 (0.13)
a
17.1
0.51 (0.09)
Sum of Loading and Moving while loading – Zbroj utovara i kretanja pri utovaru
3.15 (0.54)a
100
3.58 (0.53)a
Loading – Utovar
82.9
3.07 (0.47)
b
85.8
a
14.2
100
Biomass concentration, OD t/100 m – Koncentracija biomase, OD t/100 m
3.96 (0.38)
6.16 (0.59)
Pile size, OD t – Veli~ina slo`aja, OD t
0.17 (0.03)
0.23 (0.02)
No. crane cycles/pile – Broj ciklusa krana/slo`aj
1.00 (0.00)
1.08 (0.10)
No. piles/machine position – Broj slo`ajeva/pozicija stroja
1.15 (0.14)
1.12 (0.14)
Different superscript letters row-wise indicate significant (p £ 0.05) differences between treatments according to Tukey’s test of means
Razli~ita slova u eksponentu po redovima pokazuju zna~ajne (p £ 0.05) razlike izme|u postupaka prema Tukeyevu testu
32
Croat. j. for. eng. 33(2012)1
Productivity and Profitability of Forest Machines in the Harvesting ... (25–37)
vity in the N and O area was 0.75 and 1.02 OD
t/PW-hour, respectively. Consequently, the PW time
per ha in the N and O area was 47.8 (sd = 1.9) and 54.9
(sd = 4.7) hours, respectively. The average hauling
distance was 183 m (min. 45 m and max. 280 m). On
average, the harwarder moved at a speed of 1.2 m/s
while unloaded and 1.0 m/s while loaded. The average load mass was 1.8 OD t (3.6 t of fresh biomass),
which corresponds to 26% of the machine’s load
capacity. The average calculated bulk density of a
full load was 74 OD kg/m3 (148 fresh kg/m3). Unloading took 7.08 min/load (3.93 min/OD t) on average, and required an average of 17 crane cycles; the
mean handled mass per crane cycle was 0.11 OD t.
Miscellaneous time accounted for 0.44 minutes per
load (0.25 min OD/t). The number of harvested rows
(factor b1) had no significant effect on total PW time
consumption in the O area. The biomass density
(factor a) had a significant effect on PW time consumption (p < 0.001), and was 42% higher in the N
area compared to O area (Table 6). The mean handled mass per crane cycle during felling and loading
was 27 OD kg; for the N area (23 OD kg) it differed
significantly (p = 0.042) from that for the O area (28
OD kg). The mass moved by the crane during the
felling and loading cycle was 74% lower than the
corresponding mass while unloading. The number
of stools handled per crane cycle was 9.0 and 6.3 in
the N and O area, respectively, and the difference
was significant (p = 0.034).
Table 6 Productive work time (PW) consumed by individual work
elements in the operation of the harwarder and in total, for different
biomass densities (factor a; normal (N) and overgrown (O))
Tablica 6. Proizvodno radno vrijeme (PW) utro{eno po pojedinim
radnim elementima u radu harvardera i ukupno, za razli~ite gusto}e
biomase (faktor a, normalno (N) ili preraslo (O))
Factor a – Faktor a
Normal, N
Normalno, N
Overgrown, O
Preraslo, O
n=2
n=6
min/OD t
%
min/OD t
%
Boom out
Prazan kran
4.88 (0.76)a
6.8
4.23 (1.03)a
8.4
Felling – Sje~a
57.25 (1.36)a
80.4
38.34 (2.58)b
76.2
a
9.7
5.85 (0.70)
Moving while loading
2.19 (0.18)a
Kretanje pri utovaru
3.1
1.89 (0.43)a
3.8
71.23 (1.70)a
100
50.32 (2.99)b
100
Loading – Utovar
Sum – Zbroj
6.91 (0.24)
b
11.6
Different superscript letters row-wise indicate significant (p = 0.05) differences between
treatments according to Tukey’s simultaneously test of means
Razli~ita slova u eksponentu po redovima pokazuju zna~ajne (p = 0.05) razlike izme|u
postupaka prema Tukeyevu testu
Croat. j. for. eng. 33(2012)1
Fulvio Di Fulvio et al.
Table 7 Gross incomes, costs and net incomes for the two-machine and
harwarder systems in normal (N) and overgrown (O) willow plantations.
OD = oven-dry
Tablica 7. Bruto prihod, tro{kovi i neto dobit za sustav s dvama
strojevima i harvarder u normalnim (N) i preraslim (O) planta`ama vrba.
OD = suha tvar
Harvester and forwarder
Harwarder – Harvarder
Harvester i forvarder
Normal, N Overgrown, O Normal, N Overgrown, O
Normalno, N Preraslo, O Normalno, N Preraslo, O
Gross income, €/ha
Bruto prihod, €/ha
Cost, €/ha
Tro{kovi, €/ha
Cost, €/ODt
Tro{kovi, €/ODt
Net income, €/ha
Neto dobit, €/ha
Net income, €/ODt
Neto dobit, €/ODt
1 904
2 962
1 904
2 962
1 721
1 934
3 987
4 572
48
35
111
82
184
1 028
–2 082
–1 610
5
18
–58
–28
The mean height of the harvested stumps was
18.2 cm (min. 3 cm, max. 58 cm and median 17.5 cm).
The proportion of damaged stumps was 29.9%. No
significant differences in either stump height or proportion of damaged stumps was observed for any
treatment factors or machine/felling head types. The
average depth of the machines’ tracks after the work
was complete was 6 cm (min. 0 cm, max. 28 cm and
median 1.5 cm).
Economic Analysis
In the two-machine system, the harvester operation accounted for 75% of the total cost of the work in
the N area and 67% in the O area. The total operating
costs per hectare for the two-machine system in the
N and O areas were respectively 43% and 42% lower
than those for the harwarder (Table 7). In the O area,
the cost per harvested OD t for the two-machine
system and for the harwarder was respectively 73%
and 74% lower than the corresponding cost in the N
area. The cost to gross income ratio was below 100%
for the two-machine system, but above 100% for the
harwarder. The net income per OD t for the two
machine system was 2.6 times higher in the O area
than in the N area.
4. Discussion – Rasprava
The harvester
The biomass density (OD t/ha) (i.e. tree size) had
only a minor, non-significant, effect on the felling-bunching work time consumption per ha. The har-
33
Fulvio Di Fulvio et al.
Productivity and Profitability of Forest Machines in the Harvesting ... (25–37)
vester’s productivity was therefore 54% higher in
the O areas than in the N areas as the biomass density in O areas was 57% higher than that in N areas.
Similar results of increases in harvester productivity
have been reported in the thinning of forest stands
for energy-wood (Kärhä et al. 2005, Di Fulvio et al.
2011). Fewer harvested rows had a significant reduction effect on the harvester’s time consumption
per ha, which was due to the use of relatively shorter
crane extensions (cf. Ovaskainen 2009). In this case
the driver had a clearer view of the cutting device
and the progress of the work, resulting in more accurate control over the felling process. The working
method »forward« had no significant effect on the
harvester’s time consumption but with this method
it was easier to grab a single stool at a time than
working perpendicularly to the rows (side to side)
(cf. Fig. 2). Visual inspection indicated that the felling speed during a crane cycle was slightly reduced
cutting stems larger than ca. 3 cm dsh, which in turn
facilitated the possibility to manage a proper accumulation of the cut stems (i.e. at higher speeds it was
more difficult to manage a proper accumulation).
This suggests that modification of the accumulating
function might be necessary in order to fully exploit
the potential of this technology when harvesting at
higher speeds. To increase the potential of AFHs, the
felling and accumulation of trees must be performed
in a continuous movement, for instance by using the
boom-corridor technique (cf. Bergström 2009, Forsberg and Wennberg 2011). The harvester operator
experienced a more stressful work that required a
greater degree of concentration in the current study
(i.e. clear cutting of SRWC) compared to energy-wood thinning. This was mainly due to the handling of many more trees/stems per hour of work
time. This problem could possibly be reduced by
increasing the automation of the felling process, e.g.
by having the driver control only the felling direction and speed, with grabbing, cutting and the accumulation of stems being performed automatically.
The forwarder
The biomass density and number of harvested
rows did not significantly affect the work time required per load for the forwarder. However, the higher biomass concentration in the O area significantly
increased the loading time consumption per OD t.
This is because the pile size in the O area was 42%
larger than that in the N area; the piles in the O area
were thus larger than the grapple area and multiple
crane cycles were required per pile. The average
mass of the piles in the O area, when harvesting six
rows, was 487 kg. The force required to lift such
piles, when they are located ca. 3 m away from the
34
machine, is much less than the studied machine’s
capacity (1500 kg at 4.5 m from the crane base). The
grapple area was therefore deemed to be the limiting
factor in this work; it is expected that the efficiency of
forwarding in the O areas could be increased by
using a grapple with a larger grapple area that would
be able to load the larger piles using only one crane
cycle. In this case, estimates based on the field study
data suggest that the time consumption for loading
and moving while loading would have been decreased by 6% if all piles had been loaded with only
one crane cycle. On the basis of the field data, it was
determined that each stoppage of the machine consumed 3.5 s on average, which was added to the
»moving while loading« time element. Suppose that
in the O area, the harvester produced piles whose
sizes corresponded to either 1 or 2 full forwarder
grapples (0.216 or 0.432 OD t), with the density of
piles per loading position being high in the former
case and low in the latter. In this case, it would be
possible to describe the time spent moving while
loading as a function of the spacing between the
piles. The production of larger and more widely-separated piles would decrease the total time spent
on loading and moving while loading per OD t forwarded by 3%. Overall, these observations indicate
that the size of the piles produced by the harvester
must match the capacity of the forwarder’s grapple
in order to maximise the efficiency of forwarding, i.e.
the work of the harvester and the forwarder must be
synchronized (cf. Gullberg 1997).
The harwarder
The harwarder was equipped with an accumulating felling-grapple designed for both felling and
loading. However, because of its dual-purpose nature, the felling-grapple is less efficient at either task
than purpose-specific heads. That is to say, the number of stools felled per crane cycle with the felling-grapple was 30% lower than the corresponding
number achieved with the harvester’s AFH, and the
grapple load during unloading contained 57% less
biomass than that achieved using the slash grapple
employed in forwarding operations. In addition, the
mass of a full harwarder load was 32% lower than
that of a full forwarder load. The difference in load
mass can be explained by the fact that the forwarder
loaded pre-bunched stems, which were thus somewhat compressed, while the harwarder performed
direct-loading. It might be possible to increase the
harwarder payload by using load compression devices, such as flexible stakes attached to the bunk of
the machine (cf. Bergström et al. 2010). The time
spent on felling per stool was 3.9 times higher for the
harwarder than for the harvester (9.8 s/stool comCroat. j. for. eng. 33(2012)1
Productivity and Profitability of Forest Machines in the Harvesting ... (25–37)
pared to 2.5 s/stool). It is reasonable to assume that
the felling speed of the harwarder could be significantly increased by using more advanced technology that is better suited to industrial forestry, such
as the Ponsse EH25 felling-grapple. If we assume
that the harwarder’s felling speed could be doubled
in this way, the time consumption per stool would be
4.6 s and 5.2 s, respectively, in the N and O areas.
Such increases in felling efficiency would in turn
increase the machine’s productivity in the N and O
areas by 59% and 52%, respectively, relative to the
results obtained in the field study.
An additional increase in productivity could also
be expected with a purpose built harwarder; the one
used in this work was a standard forwarder with a
crane designed only for loading.
Work quality
The operators of the harvester and harwarder
were instructed to cut the stools to an above-ground
height of less than 10 cm. However, both felling
heads produced average stump heights in excess of
this level. This was partially due to the snow that
covered the soil when the harvesting was performed, which made it difficult to assess the true ground
level. It was also observed that when stools were cut
row-wise, the stump height rose as the boom reach
increased, i.e. the stumps were shorter close to the
machine and taller further away from it. The average
proportion of damaged stumps was 30%, which is
relatively high (cf. Hytönen 1994). It was observed
that, when using the harvester, it was possible to
grab more than one stool at a time with the AFH,
which caused the stems to bend slightly while being
cut; this in turn caused the stools to split. The tracks
left by the machines’ wheels were relatively shallow.
Harvesting was performed at a time when the soil
was partially frozen, which had a positive effect on
its bearing capacity. Using tracks on the forwarder’s
wheels (bogies) would significantly reduce the pressure it exerts on the ground, which would be especially useful on wet soils.
Economic Analysis
When using forest machines to harvest SRWC,
the productivity can be expected to increase with the
size of the stems up to a certain point. The two-machine system was found to be profitable in both
the normal and over-gown areas, while the harwarder produced a loss in both. The conventional direct
chipping system reaches an average productivity of
about 16 OD t/WT hour under conditions where the
crop yield is 25 OD t/ha (Danfors and Nordén 1995).
It would therefore be expected to achieve greater
incomes than with either of the studied forest machiCroat. j. for. eng. 33(2012)1
Fulvio Di Fulvio et al.
nes systems under normal and somewhat overgrown
conditions (cf. Danfors and Nordén 1995). However,
as the amount of biomass harvested increases, the
profitability of the forest systems increases while the
convenience and ease of operation of the conventional systems is expected to decline. This suggests that
the use of two-machine systems in more heavily
overgrown willow plantations could be even more
efficient than that of conventional direct chipping
systems.
5. Conclusions – Zaklju~ci
This study shows that a thinning harvester’s work
time consumption per hectare in the felling and
bunching of stems in SRWC plantations is meagerly
affected by stem sizes or biomass density, which
gives a harvesting productivity increase almost proportional to the increase in biomass density. The
work time consumption of the harwarder increased
significantly with biomass density, while the increase
was only minor for the forwarder. That suggests that
a harvester-forwarder system productivity would be
expected to increase significantly when harvesting
stands with average diameters greater than 5 cm at
stump height that are more overgrown than those
studied. The net income obtained using the harvester-forwarder system under the studied conditions
was positive; however, the net income achieved using the harwarder system was negative.
This study indicates that, when dealing with highly overgrown willow plantations, where ordinary
forage harvesters cannot be used, current forest machines adapted for harvesting small diameter trees may
offer an efficient and economically viable alternative. Further development of techniques and working
methods for the use of forest machines can be expected to increase their efficiency and reduce their
harvesting costs.
Acknowledgements – Zahvala
This study was financed by the Swedish Energy
Agency »Energimyndigheten«. We thank Mr. Hans
Eriksson, Västeräng Lantbruk AB, for the assistance
in field experiments.
6. References – Literatura
Anon. 2010: Prislista energisortiment. [Price list on energy
assortments] Prislista 158E 04. Norra Skogsägarna. http://
norraskogsagarna.se [accessed 2011-03-10].
Bergström, D., 2009: Techniques and systems for boomcorridor thinning in young dense forests. Doctoral thesis.
Acta Universitatis Agriculturare Sueciae, 87 p.
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Productivity and Profitability of Forest Machines in the Harvesting ... (25–37)
Bergström, D., Nordfjell, T., Bergsten, U., 2010: Compressing processing and load compression of young Scots pine
and birch trees in thinnings for bioenergy. International
Journal of Forest Engineering 21(1): 31–39.
CEN/TS 14774-2, 2004: Solid biofuels – Methods for the
determination of moisture content – Oven dry method –
Part 2: Total moisture – Simplified method.
Danfors, B., Nordén, B., 1995: Sammanfattande utvärdering av teknik och logistik vid salixskörd. Jordbrukstekniska institutet. [Summarizing evaluation of techniques
and logistic for harvesting of willow]. Uppsala, JTI-rapport, 210 p.
Di Fulvio, F., Kroon, A., Bergström, D., Nordfjell, T., 2011:
Comparison of energy-wood and pulpwood thinning systems in young birch stands, Scandinavian Journal of Forest
Research, 26(4): 339–349.
Forsberg, J., Wennberg, R., 2011: Teknikutveckling av aggregat för kontinuerlig ackumulerande skörd i unga skogar. [Technical development of a felling head for continuing accumulation at harvest in young forests] Examensarbete. Luleå tekniska universitet.
Harstela, P., 1991: Work studies in forestry. University of
Joensuu Faculty of Forestry. Joensuu. Finland. Silva Carelica 18, 41 pp.
Harstela, P., 1993. Forest work science and technology.
University of Joensuu Faculty of Forestry. Joensuu. Finland. Part 1. Silva Carelica 25, 113 pp.
Hytönen, J., 1994.: Effect of cutting season, stump height
and harvest damage on coppicing and biomass production of willow and birch. Biomass and Bioenergy 6(5):
349–357
IUFRO 1995: WP 3.04.02. Forest work study nomenclature.
Test edition valid 1995–2000. Department of Operational
Efficiency, Swedish University of Agriculture Sciences,
Garpenberg, 16 pp. ISBN 91-576-5055-1.
Laitila, J., 2008: Harvesting technology and the cost of fuel
chips from early thinnings. Silva Fennica 42(2): 267–283.
Magnusson, L., 2009: Teknik för skörd av Salix: status och
utvecklingsbehov [Technique for harvesting of willow:
status and need of development]. Slutrapport 2009–05–20.
EnerGia Konsulterande Ingenjörer AB. Stockholm.
Mitchell, C. P., Stevens, E. A., Watters, M. P., 1999: Short-rotation forestry – operations, productivity and costs on
experienced gained in the UK. Forest Ecology and Management 121 (1–2): 123–136.
Mola-Yudego, B., 2011: Trends and productivity improvements from commercial willow plantations in Sweden
during the period 1986–2000. Biomass and Bioenergy 35
(1): 446–453.
Nordh, N., Dimitriou, I., 2003: Harvest techniques in Europe. IEA Bioenergy, Task 30. Short Rotation Crops for
Bioenergy: New Zealand, pp. 115–120.
Nurmi, J., 1995: The effect of whole-tree storage on the
fuelwood properties of short-rotation Salix crops. Biomass
and Bioenergy 8(4): 245–249.
Nurminen, T., Korpunen, H., Uusitalo, J., 2009: Applying
the activity-based costing to cut-to length timber harvesting and trucking. Silva Fennica 43(5): 847–870.
Ovaskainen, H., 2009: Timber harvester operators’ working technique in first thinning and the importance of cognitive abilities on work productivity. Doctoral dissertation.
Dissertationes Forestales 79. ISSN 1795-7389. ISBN 978951-651-247-4.
Rosenqvist, H., Roos, A., Ling, E., Hektor, B., 2000: Willow
growers in Sweden. Biomass and Bioenergy 18(2): 137–145.
Sims, R., 2002: The brilliance of bioenergy in business and
in practice, James & James (Science Publishers) Ltd, Unithed Kingdom. ISBN 1-902916-28 X.
Spinelli, R., Nati, C., Magagnotti, N., 2008: Harvesting
Short-Rotation Poplar Plantations for Biomass Production.
Croatian Journal of Forest Engineering 29 (2): 129–139.
Talbot, B., Nordfjell, T., Suadicani, K., 2003: Assessing the
utility of two integrated harvester-forwarder machine concepts through stand-level simulation. International Journal of Forest Engineering 14(2): 31–43.
Verwijst, T., Telenius, B., 1999: Biomass estimation procedures in short rotation forestry. Forest Ecology and Management 121 (1–2): 137–146.
Sa`etak
Proizvodnost i profitabilnost {umskih strojeva u iskori{tavanju normalnih
i preraslih planta`a vrba
U [vedskoj se planta`e vrba u kratkim ophodnjama (PVKO) obi~no iskori{tavaju izravno iveranjem, uz primjenu krmnih kombajna opremljenih zaglavljima za rezanje drva i prijamnim bunkerima za transport usitnjene
biomase do ceste. Krmni kombajni kori{teni u PVKO imaju nedostatak u tome {to ne mogu u~inkovito prikupljati
stabljike deblje od 6 do 7 cm u visini panja. Mo`e se o~ekivati da }e u budu}nosti planta`e vrbovih panja~a postizati
vi{e prinose biomase zbog uzgajanja novih klonova te }e se prosje~ni promjeri pridobivanih stabala vjerojatno
pove}ati, {to }e stvoriti potrebu za takvim kombajnima koji mogu raditi s ve}im stablima. Mogu}a alternativa u
36
Croat. j. for. eng. 33(2012)1
Productivity and Profitability of Forest Machines in the Harvesting ... (25–37)
Fulvio Di Fulvio et al.
pridobivanju biomase na takvim planta`ama mogu biti {umski strojevi s ugra|enim akumulativnim sje~nim
glavama (ASG) razvijenim za sje~u malih stabala za bioenergiju u prvim proredama. Cilj je ovoga istra`ivanja bio
utvrditi utro{ak vremena i usporediti tro{kove primjene dvaju sustava {umskih strojeva u normalnim (N) i
preraslim (O) PVKO, pri ~emu je gusto}a promatrane biomase iznosila 36 i 56 tona suhe drvne tvari po hektaru.
Prvi strojni sustav uklju~io je harvester i forvarder, a drugi se sastojao od harvardera (sustav od jednoga stroja).
Sje~a i usnopljivanje pomo}u harvestera istra`ivani su kao funkcija gusto}e biomase, broja posje~enih redova i
smjera sje~a–usnopljivanje. Potro{nja radnoga vremena forvardera analizirana je s obzirom na gusto}u biomase i
broj po`etih redova. Potro{nja radnoga vremena harvardera analizirana je u ovisnosti o gusto}i biomase i broja
posje~enih redova. Proizvodnost je harvestera bila 54 % ve}a na O povr{ini nego na N povr{ini, i iznosila je 9 %
vi{e pri pridobivanju pet nego {to je pri pridobivanju {est duplih redova. Smjer sje~a–vezanje u snopove nije imao
zna~ajan utjecaj na proizvodnost harvestera. Gusto}a biomase i broj sje~enih redova nisu zna~ajno utjecali na utro{ak vremena po tovaru forvardera. Kod harvardera gusto}a je biomase zna~ajno utjecala na potro{nju vremena po
tovaru. Ono je u usporedbi s O povr{inom bilo 42 % ve}e na N podru~ju, dok broj posje~enih redova nije imao
signifikantan utjecaj. Harvarder je bio opremljen s akumulativnom sje~no-hvatnom glavom koja je dizajnirana za
oboje, i za sje~u i za utovar, i tada je vrijeme utro{eno na sje~u po panju bilo 3,9 puta ve}e nego za harvesterovu
ASG. Pri pridobivanju i izvo`enju biomase na udaljenosti od 250 m proizvodnost sustava s dvama odnosno s jednim {umskim strojem iznosila je prosje~no 2,3 (sd = 0,6) odnosno 0,9 (sd = 0,2) tona suhe drvne tvari/proizvodni
radni sat. Gusto}a biomase ili veli~ina stabla imali su sporedni u~inak na potro{nju vremena po hektaru za sustav s
dvama strojevima, ali su zato zna~ajni kod sustava s jednim strojem. Proizvodnost sustava s dvama strojevima i
sustava s jednim strojem u O podru~ju iznosila je u usporedbi s N povr{inom 40 % odnosno 36 % vi{e. Ukupni
tro{kovi rada po hektaru za sustav s dvama strojevima na N i O povr{inama bili su za 43 % odnosno 42 % ni`i nego
tro{kovi rada harvardera. Neto je dobit bila pozitivna kada je kori{ten sustav harvester–forvarder, a kada je
primijenjen harvarder, neto je dobit bila negativna. Neto dobit po toni suhe tvari kod sustava s dvama strojevima
bila je 2,6 puta ve}a u O podru~ju nego je to u N podru~ju. Zaklju~uje se da s pove}anjem koli~ine biomase koja se
pridobiva profitabilnost {umskih sustava raste, dok se za konvencionalne sustave o~ekuje da pogodnost i jednostavnost njihova rada opadaju. Prema tome, ako se radi o vi{e preraslih planta`a nego {to je to u primjeru, {umski
strojevi i posebno sustav harvester–forvarder mogu ponuditi u~inkovitu i ekonomi~nu alternativu uobi~ajenim
krmnim kombajnima. Daljnji razvoj tehnika i radnih metoda u upotrebi {umskih strojeva mo`e pridonijeti
o~ekivanomu pove}anju njihove u~inkovitosti i smanjenju tro{kova pridobivanja biomase.
Klju~ne rije~i: analiza sustava, studij vremena, proizvodnost, harvester, forvarder, harvarder
Authors’ address – Adresa autorâ:
Received (Primljeno): September 30, 2011
Accepted (Prihva}eno): February 07, 2012
Croat. j. for. eng. 33(2012)1
Fulvio Di Fulvio, PhD.
e-mail: fulvio.di.fulvio@slu.se
Dan Bergström, PhD.
e-mail: dan.bergstrom@slu.se
Kalvis Kons, MSc.
e-mail: kalvis.kons@slu.se
Prof. Tomas Nordfjell, PhD.
e-mail: tomas.nordfjell@slu.se
Swedish University of Agricultural Sciences
Department of Forest Resource Management
Skogsmarksgränd, SE-901 83 Umeå
Sweden
37
Original scientific paper – Izvorni znanstveni rad
Productivity of Processing Hardwood
from Coppice Forests
Christian Suchomel, Raffaele Spinelli, Natascia Magagnotti
Abstract – Nacrtak
Approximately half of the Italian forest area is classified as coppice forest, mostly managed
for the production of firewood. Chestnut (Castanea sativa Mill.) coppice stands make exception, as they also produce more valuable assortments, such as sawlogs, poles and fencing
materials. Hence the significantly higher industrial activity in chestnut coppice stands, and
the rapid introduction of mechanized harvesting. This study deals with four different harvester units used for processing (delimbing – bucking) chestnut trees from coppice stands, at
the landing. For these four different machines, time studies were conducted in order to estimate productivity and compare the performance. The results show that the processors can
reach high productivities (7.7 m3/PMH0 –19.8 m3/PMH0). In one study the influence of tree
form has been estimated, proving that the size of the branches and the shape of the stem have
a significant effect on machine productivity. The difference can reach 2.3 m3/PMH0 for
stems with a volume of 0.2 m3.
Keywords: coppice forests, processor, CTL, time study, chestnut, harvester
1. Introduction – Uvod
In Italy, coppice forests represent an important
landscape element and a significant economic resource. 54.5% of the Italian forest area is classified as
coppice forest. In the past, these stands were clear-cut
at 15 to 30 year intervals, leaving between 50 and 90
standards per hectare, with the purpose of: a) allowing the progressive regeneration of the stool base,
b) diversifying production and c) improving stand
structure. Since regeneration is obtained through stool
resprouting, these stands have a multiple stem structure. Despite a general trend towards conversion
into high forests, the majority of these stands are still
managed through coppicing. 21% of the Italian coppice forests are based on Mediterranean oaks, 18%
on chestnut (Castanea sativa Mill.), 16% on oaks, 15%
on beech (Fagus sylvatica L.), 19% on hornbeam (Carpinus betulus L.), 1% on riparian trees and 10% on
other species (INFC 2005, FAO 2005). Chestnut coppice is widespread all over Italy, but is particularly
common in the Regions of Piedmont, Tuscany, Latium, Campania and Calabria. Chestnut coppice is
seldom converted into high forest, because coppice
stands are much less vulnerable to chestnut blight
(Cryphonectria parasitica) compared to chestnut high
Croat. j. for. eng. 33(2012)1
forests. Assortments obtained from chestnut coppice
are: sawlogs, poles, fencing, firewood and woodchips. Trees from coppice generally have small size
and a basal sweep, since they grow as multiple stems
from the tree stump. Stem crowding and basal sweep
make mechanical felling difficult, which has slowed
down the introduction of modern machinery to coppice management. However, most forest companies
have recognized the crucial role of mechanization to
increase work productivity and safety, so that a growing number of harvesters and processor heads are
being deployed also in coppice operations. Felling is
done by chainsaw to guarantee that the stump is cut
near the ground level and that no fibers are pulled
out.
This research was conducted on four different
processors, in order to evaluate the factors affecting
the productivity of processing (delimbing – bucking)
pre felled chestnut trees from coppice stands, at the
landing. All trees were felled by chainsaw. Logging
was done by tractor or by cable yarder, but extraction was outside the scope of this study. The research
was conducted in cooperation between the Institute
of Forest Utilization and Work Science of the University of Freiburg and CNR IVALSA.
39
Christian Suchomel et al.
Productivity of Processing Hardwood from Coppice Forests (39–47)
2. Material and Methods – Materijal i
metode
2.1 Study layout – Prikaz istra`ivanja
Many studies have already dealt with the productivity of harvesters, showing that the main parameters influencing productivity are stem volume or
DBH (Diameter at Breast Height), tree species and
harvesting intensity (Heinimann 2001). This study is
specifically concerned with the processing (delimbing – bucking) of chestnut stems obtained from coppice stands. This work was generally conducted at
the landing and therefore the main parameters expected to affect machine productivity are: stem volume, number of logs obtained from the stem, machine
type. In addition, tree form was assumed to have a
potentially significant effect on machine productivity, and was tested as a covariate in one of the studies
composing the overall experiment.
2.2 Study sites and harvesting system
Radili{ta i sustavi pridobivanja drva
The authors studied four different harvesting machines processing pre felled chestnut trees from coppice at the landing in Northern (Piedmont) and Central
(Tuscany and Emilia Romagna) Italy. The machines
were: an Arbro 400S on a JCB 8052 excavator, a
Foresteri RH 25 on a CAT 312 L excavator, a Lako 55
Premio on a JCB JS 180 NL excavator and a Timberjack 1270B dedicated harvester with John Deere 762C
head. Even though one machine was a dedicated
harvester, all machines were part of this study. Trees
were processed at the landing so that all studied
machines had little need for moving. Therefore, locomotion technology (tracks or wheels) was likely to
have a very small impact on productivity levels. The
Foresteri Study is described as two separate experiments: in the treatment »Foresteri 1« the machine was
Table 1 Site and study conditions
Tablica 1. Mjesto i radni uvjeti
Study
Istra`ivanje
Foresteri 1
Foresteri 2
Area – Podru~je
Gaiole in Chianti (SI)
Machine – Stroj
Excavator – Bager
CAT 312 L
(71 kW, 16 t)
Head – Glava
Methods
Metoda
Species – Vrsta
Assortments
Sortimenti
DBH average
D1,30 prosjek
Lako
JohnDeere
Arbro
Abbadia S. Salvatore (SI)
Monzuno (BO)
Armeno (NO)
Signorino (PT)
Excavator – Bager
CAT 312 L
(71 kW, 16 t)
Excavator – Bager
JCB JS 180 NL
(92 kW, 19 t)
Harvester
Timberjack 1270B
(170 kW, 19 t)
Excavator – Bager
JCB 8052
(34 kW, 5 t)
Foresteri RH 25
Foresteri RH 25
Lako 55 Premio
John Deere 762C
Arbro 400S
Processing at cable
yarder landing
Izradba na pomo}nom
stovari{tu `i~are
Processing at landing
Izradba na pomo}nom
stovari{tu
Processing at landing
Izradba na pomo}nom
stovari{tu
Processing at landing
Izradba na pomo}nom
stovari{tu
Processing at landing
Izradba na pomo}nom
stovari{tu
Chestnut – Kesten
Chestnut – Kesten
Chestnut – Kesten
Chestnut with some birch
Kesten s brezom
Chestnut – Kesten
MDF pulpwood – Drvo za
plo~e
Poles
–
Stupovi
2,5 m, 15–20 cm
Poles
– Stupovi
3,5, 4,5 and 5,5 m (large
2 m, 8–12 cm
2.2 m long pulpwood;
end
up
to
20
cm,
small
end
3,5,
4,5
and
5,5 m (large
3 m, 10–15 cm
hornbeam and oak: 1,1 m
not smaller than 10 cm Process Random lengths – end up to 20 cm, small end
5 m, 15–23 cm
long firewood
promjer na debljem kraju Izradba slu~ajnih duljina
not smaller than 10 cm
5 m, 23–30 cm
promjer na debljem kraju
2,2 m celulozno drvo; grab Pulpwood – Celulozno drvo <20 cm, a na tanjem
>10 cm
<20 cm, a na tanjem
i hrast: 1,1 m ogrjevno drvo
Tops for chip production
>10 cm
Tops
for
chip
production
Ovr{ine se iveraju
Ovr{ine se iveraju
Tops for chip production
Ovr{ine se iveraju
11.9 ± 4.1 cm
19.8 ± 5 cm
15.2 ± 4.4cm
14.0 ± 3.7 cm
17.8 ± 4.3 cm
DBH (min.–max.)
4–33 cm
12–33 cm
8–34 cm
5–29 cm
8–38 cm
Cycles – Turnusi
528
136
242
840
195
Obs. time
Snimljeno vrijeme
9.1 h
2.1 h
9.4 h
13.7 h
5.8 h
40
Croat. j. for. eng. 33(2012)1
Productivity of Processing Hardwood from Coppice Forests (39–47)
working under a yarder, whereas in »Foresteri 2« it
was tending to a skidder. Table 1 shows a synthetic
description of study sites and machine characteristics.
2.3 Data collection – Prikupljanje podataka
Time-motion studies were carried out in order to
evaluate machine productivity and to identify the
variables that are most likely to affect it. Cycle times
were split into a number of time elements considered
as typical of the working process (Table 2). Time elements were recorded with a Husky Hunter hand held
field computer running Siwork3 timestudy software.
For the purpose of the study, the harvested volume was measured directly after processing or it was
calculated from the diameter at breast height (DBH),
using volume tables. In the later case, between 10
and 20 tree heights and diameters were measured
before processing the trees, in order to estimate a
DBH-height curve. Using the calculated heights and
measured DBH values, tree volumes could be estimated for each tree, using local volume tables. The
DBH of each tree to be processed was marked on the
stem or on the butt end, so that researchers could see
and note it when recording time study data. In this
study the productivity was estimated for the processed stem volume, excluding the volume eventually converted into chips (tops and branches). Waiting
times were also excluded from calculations, because
they originated from organizational causes and were
not specifically related to the stems being processed
or to the processing machines.
Data were pooled together for statistical analysis,
after adding an indicator variable describing the specific test, namely: Foresteri 1, Foresteri 2, Lako, John
Deere and Arbro. The use of indicator variables was
introduced in order to test the statistical significance
Christian Suchomel et al.
of categorical variables (here: machine type) in the
regression analysis.
The effect of tree form was investigated only in
one test (Arbro), by introducing an ordinal covariable with 5 different levels, namely: Level 1 – Small
branches, straight stems; Level 2 – Big branches or
bad form; Level 3 – Big branches and bad form, or
very big branches; Level 4 – Very big branches and
bad form, or fork and big branches; Level 5 – Forked
several times, or many big and very big branches.
This approach is widely accepted, and is recurrent in
the scientific literature on this specific subject (Spinelli et al. 2002).
2.4 Statistical analysis – Statisti~ka analiza
Analysis of variance was used to identify the influence of nominal variables on the model. Regression techniques were used to determine the relationship between productivity and work conditions. Statistical analysis was conducted with software package
SPSS 18.0 for Windows. The analytical procedure
developed as follows (as proposed by Stampfer et al.
2010): 1 – Determining the statistical significance of
co-variables through the analysis of variance; 2 –
Testing non-linear relationships of co-variables; 3 –
Analysis of the interactions between factors and co-variables; 4 – Regression analysis; 5 – Test of the
regression model (residual analysis).
3. Results – Rezultati
3.1 Model calculation – Model kalkulacija
Table 3 shows a first descriptive statistics of test
results, whereas Table 4 presents the results of the regression analysis. Net productivity excluding delays
can be modeled as follows:
Table 2 Time elements: definitions and breaking points
Tablica 2. Radni zahvati: definicije i fiksa`ne to~ke
Move
Premje{tanje
Grab
Zahvatanje
Process
Izradba
Stack
Slaganje
Product management
Uhrpavanje sortimenata
Other
Ostalo
Croat. j. for. eng. 33(2012)1
Machine starts moving – machine stops
Stroj se kre}e – stroj se zaustavlja
Machine turns into direction of tree – head arms close around the tree
Zauzimanje polo`aja – harvesterska se glava zatvara
Starts debranching and cross cutting – completes debranching and performs the last crosscut, severing the tree top
Po~etak kresanja grana i trupljenja – zavr{etak kresanja grana i zadnjega trupljenja, odrezivanje ovr{ine
Moves the top to the top pile – top falls on the pile, head arms open
Premje{tanje ovr{ine na slo`aj – ovr{ina pada na slo`aj, harvesterska se glava otvara
Take assortments and moves them to the appropriate pile – assortments dropped on the pile, head arms open
Uhrpavanje sortimenata – sortiment pada na slo`aj, harvesterska se glava otvara
Other working steps
Ostali radni zahvati
41
Christian Suchomel et al.
Productivity of Processing Hardwood from Coppice Forests (39–47)
PROD = 17.551 + 4.839ln(vol) + 0.552LOGS +
((9.707 + 1.203ln(vol) ´ DF1) +
((20.022 + 6.432ln(vol) ´ DF2) + (10.123 ´ DJD) (1)
where:
PROD
vol
LOGS
DF1
DF2
DJD
del can be used indifferently for Arbro and Lako,
after setting all dummy variables to 0.
3.2 Machine productivity – Proizvodnost
net productivity, m3/PMH0
stem volume, m3
number of logs per tree, n
Dummy variable Foresteri 1 (1 = yes, 0 = no)
Dummy variable Foresteri 2 (1 = yes, 0 = no)
Dummy variable John Deere (1=yes, 0 = no)
With an adjusted R2 of 0.667, the equation shows
a good fit. The p-value <0.001 demonstrates the high
statistical significance of our model. A dummy variable for the Lako was not included into the model
because the Arbro and the Lako had no significant
differences in productivity. That means that the mo-
Fig. 1 shows the relationship between net productivity and stem size, calculated with functions
presented above. The Foresteri appeared as the best
performer, outproducing even the dedicated harvester. However, one must keep in mind the very
wide spread of the data recorded for the dedicated
harvester, which leaves significant room for adjustment. The Lako on a JCB JS 180 NL and the Arbro on
a JCB 8052 excavator had the same productivity,
despite the very different size and mechanical characteristics. Operator effect was most likely to account for this odd result.
Table 3 Descriptive statistics
Tablica 3. Deskriptivna statistika
Cycle time [100/min]
Vrijeme turnusa, cmin
Productivity [m3/PMH0]
Proizvodnost, m3/h
Stem volume [m3]
Obujam debla, m3
Logs [n/tree]
Broj trupaca, n/stablu
Foresteri 1
Foresteri 2
Lako
John Deere
5% Quantile – Mean – 95% Quantile
5. percentile – aritmeti~ka sredina – 95. percentil
Arbro
45–78–136
50–82–132
93–160–247
30–78–169
96–153–261
1.8–7.7–17.4
8.6–19.8–34.4
0.9–5.4–10.3
8.3–16.8–34.6
4.1–9.2–14.9
0.02–0.10–0.26
0.09–0.28–0.60
0.03–0.13–0.30
0.11–0.22–0.39
0.08–0.23–0.44
3.0–7.1–14,7
1.7–3.3–5.0
1.0–2.0–3,0
1.0–2.2–4.0
1.0–2.8–4.0
Mean – Aritmeti~ka sredina
Trees/PMH0 [n]
Broj stabala, n/h
Logs/PMH0 [n]
Broj trupaca, n/efek. satu
83.9
72.8
41.8
77
39
517
241
83
168
110
Table 4 Statistical significance of model variables
Tablica 4. Statisti~ki zna~aj odabranih varijabli
Model
Model
Constant – Konstanta
ln(stem volume)
Logs – Trupci
Dummy Foresteri 1
Dummy Foresteri 2
Dummy John Deere
Dummy Foresteri 1 × ln(stem volume)
Dummy Foresteri 2 × ln(stem volume)
42
Non standardized coefficient
Standardized coefficient
Nestandardni koeficijenti
Standardni koeficijenti
Coefficient
Std. error
Beta
Koeficijent
Standardna pogre{ka
17.551
0.586
4.839
0.250
0.459
–0.552
0.055
–0.210
9.707
0.998
0.524
20.022
1.191
0.613
10.123
0.305
0.602
1.203
0.356
0.183
6.432
0.720
0.312
t-value
t-vrijednost
Significance
Zna~ajnost
29.926
19.386
–9.995
9.727
16.813
33.184
3.374
8.933
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
Croat. j. for. eng. 33(2012)1
Productivity of Processing Hardwood from Coppice Forests (39–47)
Christian Suchomel et al.
Fig. 1 Net productivity as a function of stem volume, for the different tests
Slika 1. Neto proizvodnost u ovisnosti o obujmu debla za razli~ite studije
3.3 Breakdown of Cycle times – Ra{~lamba
vremena turnusa
In all five studies, »moving« time had a very low
incidence over total cycle time, accounting for a proportion of 2.2% (Foresteri 1) to 8.5% (John Deere).
The time for »grabbing« trees represented between
15% and 24% of the total net work time. In terms
of absolute time, »grabbing« took between 12 and
23 100/min per cycle, with the Arbro and the Lako
needing the longest time (23 100/min). »Processing«
time represented the largest proportion of cycle time,
in all studies, its percent contribution increased with
tree DBH. In absolute terms, the average duration of
processing time per tree was: Foresteri 1: 40 100/min.
(with a average DBH of 11.9 cm), Foresteri 2:
49 100/min. (avg. DBH 19.8 cm), Lako: 96 100/min.
(avg. DBH 15.2, John Deere: 34 100/min (avg. DBH
14 cm, Arbro 78 100/min. (avg. DBH 17.8 cm).
»Stacking« tops after processing took between 6 and
11% of the total cycle time with the Foresteri, Lako
and Arbro machines, but grew up to 23% with the
John Deere dedicated harvester (18 100/min). The
Lako also needed 15 100/min per cycle in order to
stack tops after processing. »Product management«
included moving processed assortments to different
stacks and cleaning the work place. The contribution
of this work step to the total cycle time was the
highest with the Arbro, where it amounted to 18%
(28 100/min. absolute time per cycle). In that case, the
operator often grabbed the stems multiple times to
»organize« the woodpile. The incidence of »other«
Croat. j. for. eng. 33(2012)1
Fig. 2 Breakdown of net cycle time
Slika 2. Ra{~lamba vremena turnusa
time was the highest with Foresteri 1, because the
processor worked by the cable yarder and performed
additional ancillary tasks, such as moving the stems
away from the yarder chute and to the work area.
3.4 Delays and daily work production – Prekidi
i dnevni u~inak
Delay events lasting no more than 15 minutes
accounted for 10% to 20% of the total study time. The
incidence of delays increased to 14 to 19%, if all events
were included, regardless of their duration (Fig. 3).
The daily work production is calculated by the
equation (2):
voltotal
PRODday =
(2)
( ttotal ´ 1.44) ´ 8
where:
PRODday daily production (8 hour working day), m3
voltotal
total processed volume, m3
ttotal
total productive working time, PMH0
In this equation 31% delay time (multiplication
factor 1.44) is included as the result of a meta analysis of delay times for processing (Spinelli and Visser
2008). The daily work production derive 42.9 m3/day
for the Foresteri 1, 109.8 m3/day for the Foresteri 2,
93.1 m3/day for the John Deere, 30.0 m3/day for the
Lako and 51.1 m3/day for the Arbro.
43
Christian Suchomel et al.
Productivity of Processing Hardwood from Coppice Forests (39–47)
Fig. 3 Incidence of delay time on total study time
Slika 3. U~estalost prekida u snimljenom vremenu
3.5 Effect of tree form on machine productivity
Utjecaj oblika stabla na u~inak stroja
The effect of tree form on productivity was estimated by correlation test for the Arbro study only,
and it was taken as a general example. The five form
factors described above showed a significant effect
on productivity (confirmed by the Kendal-Tau and
Spearman-Rho tests at the 0.01 level). Form factor
was also used as an independent variable in multiple regression analysis, which returned an adjusted
R2 = 0.775. The equation is represented in Fig. 4 and
reads as follows:
PRODArbro = 22.47 + 6.25 ´ ln(vol) –
0.864 ´ LOGS – 0.573 ´ f
where:
PRODArbro Net productivity, m3/PMH0
vol
stem volume, m3
LOGS
number of logs per tree, n
f
tree form
(3)
An ANOVA shows that 68.1% of the scattering
can be explained by the variable stem volume, while
the tree form explains 2.4% of the total variability
and the number of logs 5%.
3.6 Costs – Tro{kovi
The calculated unit costs per m3 ranged from
5.05 €/m3 (for Foresteri 2) to 18.50 €/m3 (for Lako).
Detailed results and machine costs are shown in
44
Fig. 4 Net productivity as a function of stem volume and form, for the
Arbro study
Slika 4. Ovisnost neto proizvodnosti o obujmu i obliku debla za studiju
Arbro
Table 5. Very low cost was recorded especially for
highly productive machines (Foresteri and John Deere)
and cheap machines (Arbro). Hence, both strategies
seem to give good results: the choice between them
may depend on the annual work output.
Croat. j. for. eng. 33(2012)1
Productivity of Processing Hardwood from Coppice Forests (39–47)
Table 5 Machine and unit costs
Tablica 5. Tro{kovi stroja i jedini~ni tro{ak
Machine
Stroj
Foresteri 1
Foresteri 2
Lako
John Deere
Arbro
Machine costs, €/h
Tro{kovi stroja, €/h
100
100
100
130
70
Unit costs, €/m3*
Jedini~ni tro{ak, €/m3
12.90
5.05
18.51
7.74
7.60
* unit costs calculated on the basis of productivity per PMH0
* jedini~ni tro{ak izra~unat je na osnovi u~inka po efektivnom satu rada
4. Discussion and Conclusions
Rasprava i zaklju~ci
The excavator-base Foresteri deployed at a yarder
landing (Foresteri 1) processed chestnut trees with an
average diameter at breast height (DBH) of 11.9 cm.
Net productivity averaged 7.7 m3 and 89 trees per
productive machine hour (PMH0), excluding delays.
In most cases (457 cycles) the operator processed one
tree at a time. In some other cases he processed 2 (61
cycles), 3 (27 cycles) or 4 (1 cycle) trees at a time. The
calculation of different productivity functions for
total processed tree volume by cycles could not reveal
a difference in total productivity when processing
more than one tree at a time. However, the productivity was higher when processing several small trees
at a time, compared to processing them one by one.
When teaming with a skidder (Foresteri 2), the same
machine reached a net productivity of 19.8 m3 or
70 trees per productive machine hour. Productivity
was higher than in the previous study, because trees
were substantially larger, with an average DBH of
19.8 cm. Trees form was also better in the second
study. Finally, the first study was conducted at a
cable yarder landing, where the machine had to move
with much care in order to avoid damage to the
tower, the guy lines and other surrounding people
and equipment.
The productivity of the John Deere harvester was
16.8 m3 or 77 trees/PMH0. A single calculated correlation between stem volume and productivity was
weak, due to a number of factors, and especially to
the important and confounding effect of assortment
type, which was not included in the regression. Nevertheless, the significance of this function is very
high, due to the very large number of observations
used to calculate it.
The Lako harvester processed trees with an average DBH of 15.2 cm. The average tree volume was
0.13 m3. The productivity of this unit was 5.4 m3 or 41
trees per productive machine hour.
Croat. j. for. eng. 33(2012)1
Christian Suchomel et al.
The Arbro 400S was the only stroke harvester in
the study: as such, it fed stems through the delimbing knives using an alternating slide boom, rather
than rollers, like the other units observed. The average net productivity was 9.2 m3 and 39 trees/PMH0.
The range of tree DBH varied between 8 and 38 cm,
with an average of 17.8 cm.
The study showed that a full range of mechanical
processors can be successfully deployed for handling
whole chestnut trees, obtained from coppice harvesting. The processors reached high productivity and
incurred low costs. Therefore, CTL technology offers
a good alternative to motor-manual work in chestnut coppice stands to process trees at the landing
(Spinelli et al. 2009). Working at the landing and
using piles allowed the incidence of moving time,
and increasing the proportion of the actual processing (delimbing-bucking) time. Furthermore, all machines worked in coppice clearcuts (the most common
silvicultural treatment in coppice stands), with the
advantage of a concentrated volume removal.
On the other hand, coppice harvesting presents
all the disadvantages related to small tree harvesting. Stem quality is another significant factor affecting productivity, as shown in the Arbro study.
It should be particularly noted that different product strategies were followed in different studies,
and that a more accurate comparison of machine
productivity between tests could only be made if all
machines were used to produce the same assortment
range. The effect of assortment type on harvester
productivity has already been shown by other studies, reporting productivity differences between 12
and 34% as a result of different product strategies
(Emeryat et al. 1996 and 1997, Martin et al. 1996,
Sauter and Grammel 1996, Spinelli and Spinelli 2000).
Furthermore, productivity differences could partly
derive from different operator skills. The 5 machines
used for the study were operated by 5 different professionals, each representing a potential source of
unaccounted variability (Gellerstedt 2002, Purfürst
2009). The operator effect has already been shown to
affect machine productivity up to 40% (Ovaskainen
et al. 2004). Therefore, the results of these studies
must be interpreted with caution, avoiding definite
conclusions.
Acknowledgements – Zahvala
Thanks to the Deutsche Bundestiftung Umwelt
(DBU) that financed the travel costs to Italy and
made the exchange of information about harvesting
and coppice between FOBAWI and CNR IVALSA
possible. Special thanks also to the forest operators
for their help and support in the field.
45
Christian Suchomel et al.
Productivity of Processing Hardwood from Coppice Forests (39–47)
5. References – Literatura
Emeryat, R., Picorit, C., Reuling, D., 1996: L'allongement
des longueurs de billions du pin maritime. AFOCEL Fiche
Information-Forêt 531, 6p.
Emeryat, R., Picorit C. and Reuling D., 1997: Perspectives de
la mecanisation du bûcheronage du pin maritime. AFOCEL
Fiche Information-Forêt 561, 6p.
FAO, 2005: Global Forest Resource Assessment
<http://www.fao.org/forestry/static/data/fra2005/global_tables/FRA_2005_Global_Tables_EN.xls> (Accessed 1
November 2010).
Technique in Thinnings. International Journal of Forest
Engineering, 15(2): 67–77.
Purfürst, T., 2009: Der Einfluss des Menschen auf den
Harvester (The Influence of the operator on harvester).
PhD thesis at the University of Dresden, 1–307.
Sauter, U., Grammel, R., 1996: Konkurrierende Aufarbeitung von Nadelschwachholz in langer und kurzer Form
mit Kranvollerntern in der Durchforstung (Competitive
processing of conifer thinnings in long and short log lengths
by crane harvesters). Forsttechnische Informationen (6/7):
68–76.
Gellerstedt, S., 2002: Operation of the single-grip harvester: motor-sensory and cognitive work. International Journal of Forest Engineering 13(2): 35–47.
Spinelli R., Magagnotti N., Nati C. 2009: Options for the
mechanized processing of hardwood trees in Mediterranean forests. International Journal of Forest Engineering
20(1): 30–35.
Heinimann, H. R., 2001: Productivity of a cut-to-length
harvester family – an analysis based on operation data. In:
24th annual meeting of the Forest Council on Forest Engineering COFE.
Spinelli, R., Owende, P., Ward, S., 2002: Productivity and
cost of CTL harvesting of Eucalyptus globulus stands using excavator-based harvesters. Forest Products Journal
52(1): 67–77.
INFC, 2005: Ministero delle Politiche Agricole, Alimentari e
Forestali. Inventario Nazionale delle Foreste e dei Serbatoi
Forestali di Carbonio. <http://www.sian.it/inventarioforestale/jsp/home.jsp> (Accessed 1 November 2010).
Spinelli, R., Spinelli, R. 2000: L´allestimento meccanizzato
del ceduo di castagno (Mechanical cross-cutting in a chestnut coppice). Monti e Boschi 51(1): 36–42.
Martin, P., Lapeyre, D., Restoy, G., Martinez, F., Guegand,
G., 1997: Bûcheronage mécanisé en eclaircie de feuillus.
Chantier de Tournay (65), AFOCEL Note technique CW
02/97, 22p.
Ovaskainen, H., Uusitalo, J., Väätäinen, K. 2004: Characteristics and Significance of a Harvester Operators' Working
Spinelli, R., Visser, R. 2008: Analyzing and estimating delays in harvester operations. International Journal of Forest
Engineering 19(1): 35–40.
Stampfer, K., Leitner, T., Visser, R., 2010: Efficiency and Ergonomic Benefits of Using Radio Controlled Chokers in
Cable Yarding. Croatian Journal of Forest Engineering 31(1):
1–8.
Sa`etak
Proizvodnost strojne izradbe tvrdih lista~a iz panja~a
U Italiji su otprilike polovica {uma {ume panja~e ~ija je osnovna namjena proizvodnja ogrjevnoga drva. Za
razliku od ostalih, panja~e pitomoga kestena (Castanea sativa Mill.) slu`e za proizvodnju vrednijih sortimenata
kao {to su pilanski trupci, stupovi, kolje za ograde, ogrjevno drvo i drvno iverje. Stoga je proizvodna aktivnost puno
ve}a u kestenovim panja~ama te se uvode strojne metode pridobivanja drva.
Cilj je ovoga istra`ivanja odrediti proizvodnost ~etiriju razli~itih strojeva prilikom izradbe drva na pomo}nom
stovari{tu. Istra`ivane su ~etiri harvesterske glave Arbro 400S na bageru JCB 8052, Foresteri RH 25 na bageru
CAT 312L, a Lako 55 Premio na bageru JCB JS 180NL i harvester Timberjack 1270B s harvesterskom glavom John
Deere 762C. Istra`ivanje je provedeno na pet razli~itih radili{ta (tablica 1), a bavi se isklju~ivo samo izradbom drva
(kresanje grana i trupljenje). Svi su se radovi izvodili na pomo}nom stovari{tu, a glavni ~imbenici koji utje~u na
proizvodnost bili su: obujam stabla, broj sortimenata dobivenih iz stabla, vrsta stroja. Dodatno je istra`ivan utjecaj
oblika stabla (debla) na proizvodnost stroja. Za izra~unavanje u~inka uziman je samo obujam izra|ene oblovine.
Pri istra`ivanju je proveden studij rada i vremena u kojem su radni zahvati podijeljeni prema tablici 2. Obujam
je izra|enih sortimenata mjeren odmah nakon izradbe ili je bio ra~unat preko prsnoga promjera iz lokalnih
obujamnih tablica koje su napravljene samo za ovo istra`ivanje.
Nakon prikupljanja podataka napravljena je statisti~ka analiza kako je preporu~uju Stampfer i dr. (2010) te je
svakomu stroju dodijeljena opisna varijabla: Foresteri 1, Foresteri 2, Lako, Arbro, John Deer. Rezultati su statisti~ke analize prikazani u tablicama 3 i 4. Tablica 3 prikazuje rezultate deskriptivne statistike, dok tablica 4 prikazuje
rezultate regresijske analize te statisti~ki zna~aj odabarnih varijabli.
46
Croat. j. for. eng. 33(2012)1
Productivity of Processing Hardwood from Coppice Forests (39–47)
Christian Suchomel et al.
U~inak je strojeva prikazan na slici 1, na kojoj je vidljiva ovisnost u~inaka o obujmu stabla. Najve}i je u~inak
imao Foresteri 2, 109,8 m3/dan, koji je imao ve}i u~inak ~ak i od jednozahvatnoga harvestera (93,1 m3/dan). No, mora se imati na umu velik raspon snimljenih podataka za harvester, {to ostavlja mogu}nost za daljnju obradu. Iako su
priklju~ene na razli~ite bagere, harvesterske glave Lako i Arbro imale su istu proizvodnost. Usporedno s izradom
studija rada i vremena procjenjivan je utjecaj oblika debla na u~inak izradbe drva (slika 4), koja je obuhva}ena samo
u studiji Arbro. Oblik je debla kori{ten kao nezavisna verijabla, s vrijednostima od 1 do 5 (1 – male grane i ravno
deblo; 2 – debele grane ili lo{ oblik debla; 3 – debele grane i lo{ oblik debla ili vrlo debele grane; 4 – vrlo debele grane i
lo{ oblik debla ili debele grane i ra{ljavo deblo; 5 – vi{e ra{lji na deblu).
Ra{~lamba vremena turnusa za pojedine studije prikazana je na slici 2, gdje su radni zahvati podijeljeni kako je
opisano u tablici 2. Zna~ajno je da je studija za Foresteri 1 imala najve}i udjel »ostalih radnih zahvata« zato {to se
radilo o pomo}nom stovari{tu `i~are te je stroj uz osnovne zadatke morao obavljati i pomo}ne zadatke (othrpavanje
istovarne rampe `i~are). Raspon jedini~nih tro{kova strojne izrade debala kretao se od 5,05 €/m3 do 18,51 €/m3
(tablica 5).
Provedeno je istra`ivanje dokazalo da se u kestenovim panja~ama uspje{no mogu primijeniti mehanizirane
metode izradbe drvnih sortimenata, koje osiguravaju visoku proizvodnost uz niske tro{kove rada. Stoga su mehanizirane metode zadovoljavaju}a alternativa ru~no-strojnomu radu.
No, ~itatelji moraju uzeti u obzir izradbu razli~itih proizvoda koji su se izra|ivali u istra`ivanim studijama, {to
je ve} dokazano u prija{njim istra`ivanjima (Emeryat i dr. 1996, 1997, Martin i dr. 1996, Sauter i Grammel 1996,
Spinelli i Spinelli 2000), te isto tako moraju uzeti u obzir kvalitetu stabala koja utje~e na proizvodnost, {to je
dokazano u studiji Arbro. Nadalje, na razlike u proizvodnosti mo`e utjecati vje{tina operatera (Gellerstedt 2002,
Purfürst 2009) jer je svakim od istra`ivanih strojeva upravljao drugi operater. Iz navedenoga izlazi da se rezultati
ove studije moraju tuma~iti s oprezom kako bi se izbjegli kategori~ki zaklju~ci.
Klju~ne rije~i: panja~e, procesor, sortimentna metoda, studij vremena, kesten, harvester
Authors' address – Adresa autorâ:
Christian Suchomel, MSc.
e-mail: christian.suchomel@fobawi.uni-freiburg.de
Institute of Forest Utilization and Work Science
University of Freiburg
Werthmannstraße 6
79085 Freiburg
GERMANY
Received (Primljeno): November 10, 2010
Accepted (Prihva}eno): August 17, 2011
Croat. j. for. eng. 33(2012)1
Raffaele Spinelli, PhD.
e-mail: spinelli@ivalsa.cnr.it
Natascia Magagnotti, MSc.
e-mail: magagnotti@ivalsa.cnr.
CNR IVALSA
Via Madonna del Piano
50019 Sesto Fiorentino
ITALY
47
Original scientific paper – Izvorni znanstveni rad
Estimation of Machinery Market Size
for Industrial and Energy Wood Harvesting
in Leningrad Region
Yuri Gerasimov, Timo Karjalainen
Abstract – Nacrtak
The recent and coming development of forestry practices in Northwest Russia includes fast
implementation of cut-to-length (CTL) harvesting, transfer of technology, introduction of
commercial thinnings and energy wood harvesting. The market size for industrial and
energy wood harvesting machinery was assessed for the Leningrad region. The logging
machines fleet consisted of about 700 machines for traditional tree-length technology and
120 harvesters and forwarders for CTL technology. The domestic machinery fleet is obsolete;
manufacture of domestic forest machinery has dropped in both quantity and models, and
thus imported CTL machinery is replacing domestic tree-length machinery. The results
indicate that the market for CTL machinery could be 21 harvesters, 32 forwarders and 26
short-wood trucks per year and could increase to up to 30 – 40 machines each in the future.
The maximum need for the machinery in the Leningrad region could be 50 – 60 harvesters,
forwarders and short-wood trucks per year if allowable cut and commercial thinnings were
realized in full scale. The market for energy wood harvesting machinery could be 4 biomass
forwarders, 11 mobile chippers and 13 wood chip trucks per year and could be 6 and 15 – 20
machines per year in the future, respectively. The maximum need could be 30 – 40 biomass
forwarders, mobile chippers and wood chip trucks per year. Only one third of the logging
enterprises in the region had enough leased forest resources for applying the highly productive mechanized CTL technology. These 41 forest enterprises would need 270 machines, consisting of 90 harvesters, 100 forwarders and 80 short-wood trucks. Thirty-seven enterprises
would need about 50 biomass forwarders and chippers and 60 wood chip trucks for energy
wood harvesting. Sixty percent of the forest leasers had enough forest resources and could be
users of Nordic CTL technology if allowable cut was utilized completely and if commercial
thinnings were done in full scale. These 68 enterprises would need about 500 conventional
logging machines, consisting of 160 harvesters, 190 forwarders and 150 short-wood trucks,
and about 300 energy wood harvesting machines, consisting of 100 biomass forwarders, 100
chippers, and 110 wood chip trucks. In addition, the ten largest enterprises would need half
of the total fleet.
Keywords: Russia, industrial wood, energy wood, harvester, forwarder, truck, mobile chipper
1. Introduction – Uvod
A remarkable growth is expected in Russian forest machine markets in the long run mainly because
a thorough renewal of the current logging machines is required and because of a huge cutting potential within Russian forests. The development of
using different logging methods, such as cut-to-length (CTL), full-tree (FT), and tree length (TL)
method is going to have a significant influence on
Croat. j. for. eng. 33(2012)1
the share between Russian forest machine markets
(Karvinen at al. 2011).
The Leningrad region is one of the key customers
for wood harvesting machinery in Northwest Russia,
as this region is one of the major producers of forest
products. The total growing stock of the region is
approximately 797.7 million m3, of which at least 400
million m3 is available for wood supply. Approximately 35% of the growing stock is pine, 29% spruce,
25% birch, 9% aspen and 2% other tree species.
49
Y. Gerasimov and T. Karjalainen
Estimation of Machinery Market Size for Industrial and Energy Wood ... (49–60)
Fig. 1 Location of the largest logging and forest industry enterprises in Leningrad region
Slika 1. Polo`aj najve}ih poduze}a za izvo|enja radova pridobivanja drva i preradbu drva u Lenjingradskoj regiji
About 2.1 million hectares of the region’s forests are
considered to be commercial forests, where harvestable crops can be grown for timber purposes, while
2.4 million hectares are protected from harvesting
based on legislation and policy. The annual allowable cut has been about 7.9 – 9.6 million m3 under
bark (u.b.) in recent years; made up of 41% of coniferous and 59% of deciduous tree species. The actual
harvest in 2006 was 8.2 million m3, including 5.3 million m3 from final felling, 1.4 million m3 from thinnings, and 1.5 million m3 from other fellings (Gerasimov et al. 2009, Kareliastat 2010).
The region produces 4% of the industrial round
wood, 13% of the pulp and paper, and 5% of the sawn
timber in Russia. The forest industry contributes
significantly to the Leningrad region economy. The
forest industry makes up over 16% of the region’s total industrial production and employs 16% of the industrial workforce. The structure of forest industries
for this region is quite diverse. There are vertically
integrated holdings, including different combinations of pulp and paper mills, sawmills, and logging
enterprises. There are also independent companies,
50
including small and medium sized enterprises, supporting companies and organizations. The forest industry collapsed in 1990 after the dissolving of the
USSR, and stabilized between 1995 and 1998. There
was a growing period between 1998 and 2000 due to
the local currency default but there has been stagnation since 2004 in products other than lumber and
fiberboards.
Fig. 1 maps the key forest industry enterprises in
the Leningrad region. Pulp and paper mills are located in Svetogorsk (ZAO »International Paper«), Sovetsky (OAO »Vyborgskaya tseluloza«) and Syasstroy
(OAO »Syasky TsBK«). Svetogorsky P&P consumes
1.6 mill m3 u.b. of pulpwood per year, »Vyborgskaya
tseluloza« 0.4 million m3 per year, and Syasky P&P
0.5 million m3 per year, respectively. The sawmill
industry includes approximately 100 companies. The
three largest companies produce 80% of the total
sawn timber in the Leningrad region. The most important sawmills are OOO »SvirTimber« (Metsäliitto-Botnia, Podporozhye), OOO »Swedwood-Tikhvin«
(IKEA, Tikhvin), OOO »Mayr-Melnhof-Holz Efimovsky« (Efimovsky). The wood-based boards industry
Croat. j. for. eng. 33(2012)1
Estimation of Machinery Market Size for Industrial and Energy Wood ... (49–60)
in the Leningrad region includes fiberboard mill
»Lesplitinvest« in Priozersk and particleboard mill
»Zavod Nevsky Laminat« in Dubrovka. The energy
wood industry in the Leningrad region includes
wood pellet production. There are about 20 mills
with a total capacity of over 700 thousand tons per
year. Most of the forest industry capacity is concentrated in a few administrative districts with well-developed forest operations, such as Tikhvinsky,
Vyborgsky, Priozorsky and Podporozhsky.
The recent development of forest operations in
the Leningrad region includes a fast implementation
of cut-to-length (CTL) harvesting, transfer of technology, introduction of commercial thinnings and energy wood harvesting. Traditional Russian wood harvesting systems have been used side-by-side with
Nordic technology. Logging enterprises in the Leningrad region play an important role in wood procurement for relatively developed forest industry in
Northwest Russia. They have been among the most
important suppliers of the Russian regions for the
European forest industry, exporting up to 3 million
m3 of industrial round wood annually (Gerasimov
and Karjalainen 2006). Logging enterprises are deeply rooted in the local communities and involved in
the socio-economic development of rural districts in
the region.
This study has been prepared as a part of the
project »Possibilities for Energy Wood Procurement
and Use in Northwest Russia« at the Finnish Forest
Research Institute. The aim of the project was to
estimate the availability of different energy wood
sources as well as their technical and economic availability in the Leningrad region, to design cost effective energy wood procurement systems, and to
assess needs for technology development. In this
paper the machinery market size for industrial and
energy harvesting was estimated.
2. Methods and data – Metode i podaci
2.1 Identification of the market – Identifikacija
tr`i{ta
The total global market for forest machinery is
likely to be 6 000 – 8 000 machines per year, of which
3 000 could represent CTL machines (Asikainen
2005). If the logging business in Europe and Russia is
mechanized rapidly and if the marketing takeover in
South and North America is successful, the annual
volume may rise to 10 000 machines. The total
Russian market for wood harvesting machinery is
approximately $150 million per year; and imports
account for half of the total market (Belikov 2007).
Domestic machinery production has collapsed after
Croat. j. for. eng. 33(2012)1
Y. Gerasimov and T. Karjalainen
the collapse of the USSR in both quantity and models
(Eremeev 2010) e.g. from over 20 000 harvesting
machines per year in the Soviet time to 758 in 2008.
Therefore, importing of machinery has been increasing substantially and was estimated to reach 500
machines or over 200 million Euros in the near future (Grishkovets 2006). Relief of customs duties on
the imported high-tech equipment further improves
opportunities to sell overseas machinery to Russia.
The fleet of tree-length forest machines in Russia
was estimated to be 23 000 machines including the
machines imported from North America (Eremeev
2007, 2010). There are 22 enterprises producing wood
harvesting and supportive equipment in Russia
(Nekhamkin 2007), but the market has an oligopoly
character: over 90% of the machines were produced
by Onego (37%) and Altay (54%) tractor plants.
There were 26 domestic models of skidders and 16
models of feller-bunchers and delimbers. Western
forest machines for the full-tree method were available on the Russian market, such as John Deere and
Caterpillar with 12 models of feller-buncher, skidder
and delimber. However, the share of western machinery in the total Russian tree-length fleet was small;
only 8% (Eremeev 2010). The traditional producer of
wood harvesting machines, mostly cable skidders,
for Northwest Russia and Leningrad region was Onego tractor plant. Between 1970 and 1988, Onego tractor plant produced 10 – 12 thousand skidders per year
(50% of the total production in the USSR). Production dropped dramatically during the »perestroyka«
period. According to Derfler et al. (2003) the average
age of machines increased from 5 to 12 years between 1992 and 2000. Eighty percent of machines
were utilized over a standard lifetime (Eremeev 2010).
As a result, the availability rate of the machinery has
decreased from 0.9 to 0.5. This means that only half
of the total Russian harvesting machine fleet was in a
good state, i.e. that their operating/working conditions met the common requirements. The wear rate
of domestically made machines (depreciation loss) is
0.7 – 0.8.
The harvesting technology has been reorganized
all over Russia. The CTL method is getting more and
more common due to economical, ecological and
social pressures from both inside and outside of Russia. The traditional Russian wood harvesting systems are used side-by-side with Nordic technology.
Nowadays in Russia more than 24% of wood is
harvested with the CTL method including 18% harvested with a harvester and forwarder. The fleet of
CTL technology in Russia was estimated to be 2 000
machines; mostly imported machines (Nekhamkin
2007) including about 1 000 harvesters and forwarders
in Northwest Russia. The share of fully mechanized
51
Y. Gerasimov and T. Karjalainen
Estimation of Machinery Market Size for Industrial and Energy Wood ... (49–60)
CTL technology has been increasing since 2000. The
reason was the increasing import of harvesters and
forwarders mainly produced in Nordic countries.
Interchangeability of harvesters and forwarders was
constantly growing and machines were working in
2 – 3 shifts. Approximately 500 harvesters and forwarders were imported to Russia annually (Belikov
2007). Three manufacturers dominated on the CTL
machinery market in Northwest Russia: John Deere
Forestry with 55%, Ponsse with 20% and Komatsu
Forestry with 16% of the total market (Belikov 2007,
Nekhamkin 2007). Medium sized purpose-built machines such as John Deere Forestry (harvester 1270
and forwarders 1010/1410), Ponsse (harvesters Ergo
and Beaver, forwarders Buffalo) and Komatsu Forest
(harvesters Valmet 911/901, forwarder Valmet 860)
were the most common CTL machinery. Light or
small sized harvesters were not that common. Heavy
harvesters were usually based on excavators (Volvo
EC210B, Kobelco SK 135, Hitachi Zaxis 230) (Gerasimov and Sokolov 2008). Russian forest machine
manufacturers have tried to design and produce domestic harvesters and forwarders, but have been
unsuccessful.
2.2 Identification of the customers
Identifikacija korisnika
Once the key markets for wood harvesting technology in the Leningrad region were identified, the
next step was to identify segments and customers
that make up a large potential for forest machine
sales in the region. Russian end-users of forest harvesting machines were generally logging enterprises
with leased forests and in some cases contractors.
Some large enterprises had wood harvesting employees within the firm. Most of the enterprises that
contract out or hire wood harvesting employees were
large firms that specialized in producing sawn timber, pulp and paper, or both. Due to productivity and
environmental pressures, those end-users need mobile, versatile, efficient, and environmentally friendly wood harvesting machinery. Technological and
environmental changes and requirements mean continuing growth and development of this market. The
challenge of adhering to strict environmental regulations in the face of intense competition has increased
the demand for new CTL machinery systems for
wood harvesting in the region.
The total number of logging enterprises officially
registered in the Leningrad region was about 1 000
with over 12 000 employees (Kareliastat 2010); however, only 113 enterprises leased forests for wood
supply. Harvesting operations were concentrated into
large and medium-sized enterprises, which usually
belong to international pulp and woodworking mills.
52
Fig. 2 Distribution of logging enterprises (forest leasers) based on their
actual annual harvest
Slika 2. Podjela poduze}a za izvo|enje radova pridobivanja drva
(koncesionari {uma) s obzirom na njihov stvarni godi{nji etat
The annual allowable cut of the 30 largest forest
leasers was about 5 million m3 with the actual harvest of 3 million m3. The four largest logging companies accounted for the annual harvest volume of
more than 200 000 m3, OAO »Svetogorsk« (International Paper) and OOO »Metsyaliitto Podporozhje«
(Metsäliitto) representing the key players in pulp
and paper industry. They harvested about 26% of the
actual annual cut in the Leningrad region. The companies with 100 – 200 thousand m3 of harvested wood
per year, i.e. OOO »Svedwood-Tikhvin« (IKEA) and
ZAO »Efimovsky KLPKh« (Mayr-Melnhof-Holz),
represented the largest players in sawmilling. The
share of these companies was approximately 20% of
the actual annual harvest in the Leningrad region.
This means that only 9 key companies procured
approximately half of the region’s annual harvest.
The next 14 companies with 50 – 100 thousand m3 of
harvested wood per year provided about 30% of the
actual annual harvest in the region. Approximately
50 small companies harvested the remaining 20% of
the wood (Fig. 2). Fig. 1 maps the operation areas of
the largest logging enterprises in the Leningrad region. Most of the logging capacity was concentrated
among a few forest districts with well developed
forest industry, such as Tikhvinsky, Priozorsky and
Podporozhsky.
2.3 Scenarios for the estimation of machinery
market size – Scenariji za procjenu veli~ine
tr`i{ta strojeva
Gerasimov and Karjalainen (2011) have analyzed
the development of industrial and energy wood resources based on trends in logging and woodworking in Northwest Russia including the Leningrad
region. The overall development of wood procurement in the Leningrad region and woodchip proCroat. j. for. eng. 33(2012)1
Estimation of Machinery Market Size for Industrial and Energy Wood ... (49–60)
duction in particular will require a large amount of
forestry machines and wood transport vehicles. The
estimation of machinery market size for industrial
and energy harvesting in the region was based on
three scenarios (Gerasimov et al. 2007): »Actual«,
»Allowable«, and »Potential«.
Scenario »Actual« assumed continuing the current
level of wood harvesting. It means the current utilization of annual allowable cut with a 40% use of the
CTL method. The estimated potential for energy wood
from logging operations was 3.5 million m3/year
based on 7.9 million m3 of the actual harvest. About
2.3 million m3 was non-industrial round wood and
felling residues in the cutting areas and 1.2 million
m3 derived from the central processing yards. The
volume harvested with CTL technology was 3.2 million m3 within 40% of the total annual cut.
Scenario »Allowable« assumed increasing availability of energy wood resources based on full utilization of the annual allowable cut, utilizing the current logging technology and increasing production
of sawn timber in accordance with the green-field
projects, such as Svir-Timber sawmill, Mayr-Melnhof-Holz Efimovsky, etc.; see Fig. 1. The Allowable
scenario means that the volume of the annually harvested stem wood in the final felling would increase
from 5.1 million m3 to 9.5 million m3. It is assumed
that the current proportions in logging technologies
will remain the same, i.e. 40% of the CTL method,
but that the share of felling by harvesters will increase from 1/3 to 2/3. The amount of energy wood
Y. Gerasimov and T. Karjalainen
available from logging could be as high as 5.3 million m3 if the entire annual allowable cut of 9.5 million m3 were utilized, if collected. About 3.3 million m3
is non-industrial round wood and felling residues in
the cutting areas. The volume harvested by CTL
technology is 4.9 million m3 (40% of the total allowable cut).
Scenario »Potential« assumed increasing availability of energy wood due to the implementation of
intensive forest management; resulting from a significant increase of commercial thinnings, full utilization of annual allowable cut with CTL technology,
and increasing production of sawn timber in accordance with the available sawlog output in the region
(no export). According to the Potential scenario, commercial thinnings would increase from 1.5 million
m3 to 4.6 million m3 with 100% implementation of
mechanized CTL technology (harvester and forwarder). The amount of energy wood available from
logging could be as high as 7.2 million m3 if thinnings were also done in full scale, if collected. The
assumption is that all harvesting is carried out with
CTL technology, i.e. 15.3 million m3 of which 40% is
from thinnings.
The annual average productivity of wood harvesting machines was obtained from different statistical and companies' data in Russia and Finland
(Goltsev et al. 2010a, Goltsev et al. 2010b, METLA
2010, Gerasimov et al. 2011). Assumptions about the
annual productivity of CTL and energy wood
harvesting machines are presented in Fig. 3.
Fig. 3 Average annual productivity of CTL industrial and energy wood harvesting machines used to estimate the machinery market size
Slika 3. Prosje~na godi{nja proizvodnost strojeva za pridobivanje industrijskoga i energijskoga drva sortimentnom metodom koja se koristila za procjenu
veli~ine tr`i{ta strojeva
Croat. j. for. eng. 33(2012)1
53
Y. Gerasimov and T. Karjalainen
Estimation of Machinery Market Size for Industrial and Energy Wood ... (49–60)
Table 1 An estimation of the wood machinery fleet with three scenarios for the Leningrad region
Tablica 1. Procjena broja {umskih strojeva prema trima scenarijima za Lenjingradsku regiju
Source – Sredstvo
Logging, mill. m3 – Drvni obujam, mil. m3
Mobile chipper, units/year – Pokretni ivera~i, kom./god.
Chip trucks, units/year – Kamioni za prijevoz drvnoga iverja, kom./god.
Forwarders for round wood and loose logging residues, units/year
Forvarderi za oblo drvo i {umski ostatak, kom./god.
Harvesters, units/year – Harvesteri, kom./god.
Trucks, units/year – Kamioni, kom./god.
Scenario for harvesting round wood (RW) and energy wood (EW)
Scenarij za pridobivanje obloga drva (RW) i energijskoga drva (EW)
Actual – Trenutni
Allowable – Dopustivo
Potential – Mogu}e
RW
EW
RW
EW
RW
EW
3.2
2.3
4.9
3.3
15.3
7.2
–
77
–
110
–
240
–
92
–
132
–
288
93
31
144
44
451
240
28
74
–
–
88
114
–
–
417
356
–
–
mobile chippers, 132 chip trucks and 44 forwarders
for loose logging residues.
The maximum theoretical need for CTL machinery in the Leningrad region could be about 400 units
of forwarders, harvesters and short-wood trucks,
plus about 250 units of mobile chippers, chip trucks
and forwarders for loose logging residues.
Table 2 shows the estimated market size for the
CTL and energy wood machinery when the need to
renew traditional tree-length machinery is also taken
into account and replaced by CTL machinery:
Þ Scenario »Actual«. Actual annual harvest is stable; a traditional technology was replaced by CTL
technology according to machinery wear out; the
felling process was mechanized by 1/3; forest
machines were replaced every 7th year;
Þ Scenario »Allowable«. Actual annual harvest grew
from 7.9 to 15.3 million m3 by 5% per year; traditional technology was replaced by CTL technology according to machinery wear out; the felling
process was mechanized by 2/3; forest machines
were replaced every 7th year;
3. Results – Rezultati
3.1 Estimation of machinery market size for the
region – Procjena veli~ine tr`i{ta strojeva za
regiju
Table 1 shows the CTL machinery fleet for industrial wood harvesting, which was 93 for forwarders,
28 for harvesters and 74 for short-wood trucks for
the actual harvest, according to the average annual
productivity. The energy wood machinery fleet for
full utilization of the available energy wood resources at the cutting areas could be 77 for mobile chippers, 92 for chip trucks and 31 for forwarders for
loose logging residues.
If the allowable cut were realized in the Leningrad region based on the current degree of mechanization in the industrial wood harvesting, the need for
CTL machinery fleet would be about 144 forwarders
(+50%), 88 harvesters (+200%) and 110 short-wood
trucks (+50%). The theoretical energy wood machinery fleet in the Leningrad region would be 114
Table 2 An estimation of the wood machinery fleet with three scenarios for the Leningrad region
Tablica 2. Procjena veli~ine tr`i{ta {umskih strojeva prema trima scenarijima za Lenjingradsku regiju
Source – Sredstvo
Logging, mill. m3 – Drvni obujam, mil. m3
Mobile chipper, units/year – Pokretni ivera~i, kom./god.
Chip trucks, units/year – Kamioni za prijevoz drvnoga iverja, kom./god.
Forwarders for round wood and loose logging residues, units/year
Forvarderi za oblo drvo i {umski ostatak, kom./god.
Harvesters, units/year – Harvesteri, kom./god.
Trucks, units/year – Kamioni, kom./god.
54
Scenario for harvesting of round wood (RW) and energy wood (EW)
Scenarij za pridobivanje obloga drva (RW) i energijskoga drva (EW)
Actual – Trenutni
Allowable – Dopustivo
Potential – Mogu}e
RW
EW
RW
EW
RW
EW
3.2
2.3
4.9
3.3
15.3
7.2
–
11
–
16
–
34
–
13
–
19
–
41
32
4
40
6
64
34
21
26
–
–
30
30
–
–
60
51
–
–
Croat. j. for. eng. 33(2012)1
Estimation of Machinery Market Size for Industrial and Energy Wood ... (49–60)
Þ Scenario »Potential«. Actual annual harvest of
15.3 million m3; traditional technology was totally replaced by CTL technology; fully mechanized
felling process with harvester; forest machines
were replaced every 7th year.
According to the Actual scenario, the use of CTL
machinery would require an annual purchase of 32
forwarders, 21 harvesters and 26 short-wood trucks.
The annual market for energy wood machinery could
be 11 mobile chippers, 13 chip trucks and 4 forwarders for loose logging residues, if energy wood
from the current logging operations were collected.
If the allowable cut is realized in the Leningrad
region based on the current level of mechanization,
the annual market for CTL machinery could be 40
forwarders (+20%), 30 harvesters (+40%) and 30
short-wood trucks (+20%). In this case, the market
for energy wood machinery in the Leningrad region
could be 16 mobile chippers, 19 chip trucks and 6
forwarders for loose logging residues per year.
If thinnings were also done in full scale, the market for energy wood machinery in the Leningrad
region could be 50 – 60 units/yr of forwarders, harvesters and short-wood trucks, plus 30 – 40 units/yr
of mobile chippers, chip trucks and forwarders for
loose logging residues.
3.2 Estimation of machinery market size for
logging enterprises with leased forests
Procjena veli~ine tr`i{ta strojeva za
poduze}a za izvo|enje radova pridobivanja
drva s koncesijom nad {umama
Many small size enterprises with minor leased forests are operating in the Leningrad region without
financial possibilities to make investments into modern CTL technology. Therefore, it is useful to make
the detailed estimation of the harvesting machinery
fleets for a company level. Tables 3 – 5 show the need
for CTL and energy wood machinery fleets based on
assumptions in Table 1, but at the company level, i.e.:
Þ Number of harvesters, forwarders and short-wood
trucks (CTL machinery) and mobile chippers, biomass forwarders and chip trucks (energy wood
machinery), calculated based on Actual (Table 3),
Allowable (Table 4), and Potential (Table 5) scenarios in the leased forests of individual enterprises,
Þ Energy wood potential of forest units of the Leningrad region where leased forests are taken
into account (Gerasimov et al. 2007),
Þ Data about leased forests provided by the Federal
Forest Agency of Russia,
Þ Whole volume harvested by fully mechanized CTL
technology (using harvesters and forwarders),
Croat. j. for. eng. 33(2012)1
Y. Gerasimov and T. Karjalainen
Þ Annual productivity of machines as presented in
Fig. 3,
Þ Number of machines (rounded).
Fig. 4 Number of perspective forest leasers in Leningrad region and
their need for CTL machinery fleet in three scenarios
Slika 4. Broj koncesionara {uma u Lenjingradskoj regiji i njihova potreba za {umskim strojevima za pridobivanje drva pri sortimentnoj metodi
izrade drva prema trima scenarijima
Fig. 5 Number of perspective forest leasers in Leningrad region and
their need for energy wood harvesting machinery fleet in three scenarios
Slika 5. Broj koncesionara {uma u Lenjingradskoj regiji i njihova potreba za {umskim strojevima za pridobivanje energijskoga drva prema
trima scenarijima
55
Y. Gerasimov and T. Karjalainen
Estimation of Machinery Market Size for Industrial and Energy Wood ... (49–60)
Fig. 4 shows the number of perspective forest
enterprises with leased forests in the Leningrad region and their need for CTL machinery fleet in three
scenarios. Fig. 5 shows the number of perspective
forest enterprises and their need for an energy wood
machinery fleet.
Table 3 Estimation of the machinery fleet by forest leasers according to »Actual« scenario
Tablica 3. Procjena brojnosti {umskih strojeva kod koncesionara {uma prema »trenutnom« scenariju
Number of leasers
AC, 1000 m3
Broj koncesionara
Harvesters
Harvesteri
Forwarders
Forvarderi
Timber trucks
Kamioni za
prijevoz drva
Mobile chippers Biomass forwarders
za prijevoz
Pokretni ivera~i Forvarderi
{umskoga ostatka
Woodchip trucks
Kamioni za prijevoz
drvnoga iverja
3
> 200
21
23
18
12
12
15
5
100 – 200
20
22
17
11
11
13
14
50 – 99
27
32
23
15
15
18
19
30 – 49
20
21
20
16
16
16
Total: 41
–
88
98
78
54
54
62
AC – Actual harvest in leased area – Stvarni etat na povr{ini {uma pod koncesijom
Table 4 Estimation of the machinery fleet by forest leasers according to »Allowable« scenario
Tablica 4. Procjena brojnosti {umskih strojeva kod koncesionara {uma prema »dopustivom« scenariju
Number of leasers
AAC, 1000 m3
Broj koncesionara
Harvesters
Harvesteri
Forwarders
Forvarderi
Timber trucks
Kamioni za
36
39
31
prijevoz drva
Woodchip trucks
Mobile chippers Biomass forwarders
Forvarderi
za
prijevoz
Kamioni
za prijevoz
Pokretni ivera~i
{umskoga ostatka
drvnoga iverja
3
> 400
20
20
24
1
300 – 399
9
10
8
5
5
6
5
200 – 299
32
35
28
20
20
24
8
100 – 199
27
28
22
17
17
17
24
50 – 99
47
51
38
24
24
28
27
30 – 49
27
27
27
15
15
15
Total: 68
–
178
190
154
101
101
114
AAC – annual allowable cut in leased area for final fellings – Godi{nji dopustivi etat dovr{nih sje~a na povr{ini {uma pod koncesijom
Table 5 Estimation of the machinery fleet by forest leasers according to »Potential« scenario
Tablica 5. Procjena brojnosti {umskih strojeva kod koncesionara {uma prema »mogu}em« scenariju
Number of leasers
AAC, 1000 m3
Broj koncesionara
Harvesters
Harvesteri
Forwarders
Forvarderi
Timber trucks
Kamioni za
prijevoz drva
Woodchip trucks
Mobile chippers Biomass forwarders
Forvarderi
za
prijevoz
Kamioni
za prijevoz
Pokretni ivera~i
{umskoga ostatka
drvnoga iverja
1
> 700
20
21
17
9
9
11
2
600 – 699
34
38
30
21
21
25
2
400 – 499
25
27
21
14
14
17
4
300 – 399
37
40
32
23
23
27
2
200 – 299
13
14
11
6
6
8
20
100 – 199
72
74
61
39
39
47
24
50 – 99
47
54
36
25
25
32
16
30 – 49
16
16
16
15
15
15
Total: 71
–
264
284
224
152
152
182
AAC – annual allowable cut in leased area for final fellings and commercial thinnings – Godi{nji dopustivi etat dovr{nih sje~a i proreda na povr{ini {uma pod koncesijom
56
Croat. j. for. eng. 33(2012)1
Estimation of Machinery Market Size for Industrial and Energy Wood ... (49–60)
4. Conclusions – Zaklju~ci
The results indicated that the annual market for
CTL machinery in the Leningrad region can be approximately 20 – 30 medium sized purpose-built
harvesters/forwarders and short-wood trucks, respectively. The market could be 30 – 40 units per year
in the future, if the allowable cut were utilized or
even 50 – 60 harvesters, forwarders and short-wood
trucks per year, if commercial thinnings were also
done on a full scale. The current market for energy
wood machinery can be approximately 4 biomass
forwarders, 10 mobile chippers and wood chip trucks
per year. The market could be about 15 – 20 units per
year in the future, if allowable cut were utilized or
30 – 40 biomass forwarders and mobile chippers per
year, if commercial thinnings were also done on a
full scale.
The total number of enterprises registered for
wood harvesting operations in the Leningrad region
was about one thousand, but only one hundred enterprises had leased forests and could be taken into
account as major customers of CTL machinery manufacturers. Only one third of the current forest leasers
in the Leningrad region had enough leased forest
resources and could be the users of fully mechanized
CTL technology based on the Actual scenario. These
41 enterprises needed 270 CTL machines altogether
– 90 harvesters, 100 forwarders and 80 trucks. Thirty-seven companies needed 50 chippers, 50 biomass
forwarders, and 60 woodchip trucks for energy wood
harvesting. The share of the 10 largest enterprises
would be half of the total fleet.
Sixty percent of forest leasers in the Leningrad
region had enough leased forest resources and could
be the users of fully mechanized CTL technology
based on the Allowable scenario. These 68 enterprises needed 500 CTL machines altogether – 160
harvesters, 190 forwarders and 150 trucks. Fifty-six
companies needed 100 chippers, 100 biomass forwarders, and 110 woodchip trucks for energy wood
harvesting. The share of the 10 largest enterprises
would be half of the total fleet.
Sixty percent of the current forest leasers in the
Leningrad region had enough leased forest resources and could be the users of fully mechanized CTL
technology based on the Potential scenario. These 71
enterprises would need 770 CTL machines altogether – 260 harvesters, 280 forwarders and 230 trucks.
Seventy companies would need 150 chippers, 150
biomass forwarders, and 180 woodchip trucks for
energy wood harvesting.
The wood harvesting machinery fleet in the Leningrad region was estimated at about 700 logging
machines for the traditional tree-length technology
Croat. j. for. eng. 33(2012)1
Y. Gerasimov and T. Karjalainen
and approximately 120 harvesters and forwarders
for CTL technology. In the Leningrad region the fleet
of domestic logging machinery was obsolete; the
wear rate of fixed assets was about 50% and needs an
improvement.
The actual harvest in the Leningrad region has
been about 8 million m3 in recent years and may not
increase in the near future. This study presented the
most recent publicly available official governmental
statistical data on wood harvesting and forest leasing in the Leningrad region in 2006. However, the
actual harvest volume is not a constant for various
reasons. In the period 2008 – 2010, the actual harvest
volume slightly decreased due to challenges in implementation of the new Forest Code, increasing
custom duties for round wood export, the financial
crisis of 2008 and environmental impacts (Gerasimov
and Karjalainen 2008, Karvinen et al. 2011). The same
statement is true for the annual allowable cut. Nevertheless, considering that the scenario of forest use can
have variants, the methodology of using the techniques described in this study gives some flexibility
for determining the need for harvesting machines.
The wood harvesting industry in Northwest Russia continues at the Onego tractor plant with the production of two models of traditional caterpillar skidders, but the production dropped in 1988 from
12 000 to 100 machines per year. The imported CTL
machinery is replacing domestic tree-length machinery supporting the recent development of forestry
practices in the Leningrad region including fast implementation of CTL harvesting, transfer of technology, introduction of commercial thinnings and energy wood harvesting.
The economic indexes of technology development
in wood harvesting showed positive signs, as the
renewal rate for harvesting machinery has been increasing since 2005 from 14% (2005) to 36% (2009)
(Kareliastat 2010). This means that logging enterprises are now in a better position to renew machinery and technology than in the past. Nowadays
there are also better possibilities to finance the purchase of new technology. This means that the methodology, presented in the study, is timely and able to
support the development of strategies, concepts and
programs related to the forestry mechanization in both
the Leningrad region and other regions of Russia.
Acknowledgements – Zahvala
The work was carried out for the project »Wood
Harvesting and Logistics«, financed by the European
Union through the Finnish Funding Agency for Technology and Innovation (TEKES).
57
Y. Gerasimov and T. Karjalainen
Estimation of Machinery Market Size for Industrial and Energy Wood ... (49–60)
5. References – Literatura
Asikainen, A., Ala-Fossi, A., Visala, A., Pulkkinen, P., 2005:
Metsateknologiasektorin visio ja tiekartta vuoteen 2020
(Forest technology vision and roadmap for 2020). Working
Papers of the Finnish Forest Research Institute 8, 92 p.
Belikov, D., 2007: Tehnika stvola (Stem techniques). Business Guide 70(3646): 35–36.
Derfler, A. A., Bykov, V. V., Golubev, I. G., 2003: Osnovnxe
Napravleniq Tehni~eskoj Politiki OAO Alttrak
(Main directions of technological policy of OAO Alttrak).
Timber Industry 2: 25–28.
Eremeev, N. S., 2007: Po~emu neobhodimo sohranenie i
razvitie ote~estvennogo lesnogo ma{inostroeniq
(Why necessary to safe and develop the manufacture of
domestic forest machinery). Forest Business 5: 56–58.
Eremeev, N. S., 2010: Lesnxe ma{inx iz Rossii vpolne
mogut bxty konkurentosposobnxmi na mirovom rxnke
(Forest machines from Russia can be quite competitive on
the world market). Special Machinery 3: 56–58.
METLA, 2010: Statistical Year Book of Finnish Forestry.
Helsinki: Finnish Forest Research Institute. 470 p.
Gerasimov, Y., Karvinen, S., Leinonen, T., 2009: Atlas of the
forest sector in Northwest Russia 2009. Working Papers of
the Finnish Forest Research Institute 131, 43 p.
Gerasimov, Y., Karjalainen, T., 2006: Development of wood
procurement in Northwest Russia: Round wood balance
and unreported flows. European Journal of Forest Research
125(2): 189–199.
Gerasimov, Y., Karjalainen T., 2008: Development program
for improving wood procurement in Northwest Russia
based on SWOT analysis. Baltic Forestry 14(1): 85–90.
Gerasimov, Y., Karjalainen, T., 2011: Energy wood resources
in Northwest Russia. Biomass Bioenergy 35(5): 1655–1662.
Gerasimov, Y., Karjalainen, T., Ilavský, J., Tahvanainen, T.,
Goltsev, V., 2007: Possibilities for energy wood procurement in north-west Russia: Assessment of energy wood
resources in the Leningrad region. Scand. J. For. Res. 22(6):
559–567.
Gerasimov, Y., Senkin, V., Väätäinen, K. 2011. Productivity
of single-grip harvesters in clear-cutting operations in the
northern European part of Russia. European Journal of
Forest Research. DOI: 10.1007/s10342-011-0538-9. 8 p.
Gerasimov, Y., Sokolov, A., 2008: Ergonomic characterization of harvesting work in Karelia. Croatian Journal of
Forest Engineering 30(2): 159–170.
Goltsev, V, Ilavský, J, Gerasimov, Y, Karjalainen, T., 2010:
Potential for biofuel development in Tihvin and Boksitogorsk districts of the Leningrad region – The analysis of
energy wood supply systems and costs. Forest Policy and
Economics 12(4): 308–316.
Goltsev, V., Ilavský, J., Karjalainen, T., Gerasimov Y., 2010:
Potential of energy wood resources and technologies for
their supply in Tihvin and Boksitogorsk districts of the Leningrad region. Biomass and Bioenergy 34(10): 1440–1448.
Grishkovets, E., 2006: Topornaq rabota (Clumsy work).
Business Guide 194(3525): 36–37.
Kareliastat, 2010: Lesopromx{lennxj kompleks regionov Severo-Zapadnogo Federalynogo okruga Rossii
(Forest Sector of Northwest Russian regions). Petrozavodsk, 212 p.
Karvinen, S., Välkky, E., Gerasimov, Y., Dobrovolsky, A.,
2011: Northwest Russian Forest Sector in a Nutshell. Metla,
Joensuu, 144 p.
Nekhamkin, V., 2007: Celesoobraznosty primeneniq
zarube`noj lesozagotovitelynoj tehniki (Advisa-
bility of import wood harvesting machinery utilization).
Forest Business 2 (2007): 60–63.
Sa`etak
Procjena veli~ine tr`i{ta strojeva za pridobivanje industrijskoga i energijskoga drva
u Lenjingradskoj regiji
Lenjingradska je regija jedna od najve}ih proizvo|a~a {umskih proizvoda u Rusiji te je stoga najve}e tr`i{te
{umskih strojeva za pridobivanje drva. Ukupna je drvna zaliha u regiji oko 797,7 milijuna m3. Godi{nji dopu{teni
sje~ivi etat je oko 7,9 – 9,6 milijuna m3, od ~ega na crnogori~ne vrste drva otpada 41 %, a na bjelogori~ne vrste drva
59 % etata. Stvarni sje~ivi etat u 2006. iznosio je 8,2 milijuna m3, od toga 5,3 milijuna m3 iz dovr{nih sje~a, 1,4 milijuna m3 iz proreda te 1,5 milijuna m3 iz ostalih vrsta sje~a (Gerasimov i dr. 2009, Kareliastat 2010).
Regija proizvodi 4 % industrijskoga obloga drva, 13 % celuloze i papira i 5 % od piljene gra|e u Rusiji. Poduze}a,
koja se bave pridobivanjem drva, godi{nje izvezu 3 milijuna m3 te stoga imaju zna~ajnu ulogu na drvnu industriju u
sjeverozapadnoj Rusiji i na europsku drvnu industriju (Gerasimov i Karjalainen 2006). [umarstvo i drvna industrija
Lenjingradaske regije ~ine vi{e od 16 % ukupne industrijske proizvodnje i zapo{ljavaju 16 % radne snage.
Zbog potrebe za obnovom {umske mehanizacije te zbog golemih mogu}nosti ruskih {uma o~ekuje se velik rast
tr`i{ta {umskih strojeva. Razlike izme|u metoda izrade drva (sortimentna, stablovna, deblovna metoda) imat }e
zna~ajan utjecaj na raspodjelu tr`i{ta {umskih strojeva u Rusiji.
58
Croat. j. for. eng. 33(2012)1
Estimation of Machinery Market Size for Industrial and Energy Wood ... (49–60)
Y. Gerasimov and T. Karjalainen
Daljnji razvoj sustava pridobivanja drva u Lenjingradskoj regiji razumijeva uvo|enje sortimentne metode
izrade drva i komercijalnih proreda te ve}e pridobivanje energijskoga drva. Usporedno s novim sustavima primjenjuju se i tradicionalne metode pridobivanja drva.
Na svjetskom tr`i{tu {umskih strojeva i opreme godi{nje se proda 6000 – 8000 strojeva, od ~ega 3000 otpada na
strojeve koji se koriste pri sortimentnoj metodi izrade drva (Asikainen 2005). Ako se nastavi ubrzano mehaniziranje {umskih radova u Europi i Rusiji, te ako se tr`i{tu pridodaju Sjeverna i Ju`na Amerika, godi{nje bi se moglo
prodavati i do 10 000 {umskih strojeva. U Rusiji se godi{nje tro{i oko $150 milijuna eura na kupovinu {umskih
strojeva, a polovica te vrijednosti otpada na uvoz (Belikov 2007). Doma}a industrija {umskih strojeva i opreme
naglo je propala raspadom SSSR-a – proizvodnja je pala s 20 000 proizvedenih strojeva godi{nje na samo 758
strojeva u 2008. godini. Stoga je uvoz bitno rastao te se procjenjuje da bi mogao dose}i vrijednost od 200 milijuna
eura/god. odnosno 500 strojeva/god. (Grishkovets 2006).
Procjenjuje se da sada u Rusiji ima 23 000 {umskih strojeva, uklju~uju}i uvezene strojeve iz Sjeverne Amerike
koji su ve}inom prilago|eni za deblovnu metodu izrade drva (Eremeev 2007, 2010). Prema Derfleru i dr. (2003)
strojevi imaju prosje~no izme|u 5 i 12 godina. Osamdeset posto strojeva koristi se dulje od amortizacijskoga roka
(Eremeev 2010).
Krajnji su korisnici {umskih strojeva uglavnom poduze}a koja imaju koncesiju nad {umama ili privatni
izvo|a~i radova. Zbog potrebe za pove}anjem proizvodnosti i stro`ih ekolo{kih propisa pove}ava se potreba za raznovrsnijim, u~inkovitijim i okoli{no pogodnijim {umskim strojevima. Zbog toga u posljednje vrijeme sortimentna
metoda izrade drva postaje sve u~estalija. Procjenjuje se da u primjeni sortimentne metode izrade drva u Rusiji ima
2000 ve}inom uvezenih strojeva. Njihov je broj od 2000. godine u stalnom porastu te se procjenjuje da se danas u
Rusiju uveze oko 500 harvestera i forvardera na godinu.
Za potrebe procjene veli~ine tr`i{ta {umskih strojeva u ovom su radu postavljena tri scenarija: »trenutni«,
»dopustivi« i »mogu}i«.
Þ »Trenutni« se scenarij zasniva na postoje}em stupnju pridobivanja drva, tj. na godi{njem etatu od
7,9 mil. m3/godi{nje od ~ega se 40 % etata izra|uje sortimentnom metodom, a 3,5 mil. m3 odnosi se na
energijsko drvo.
Þ »Dopustivi« se scenarij temelji na pove}anju pridobivanja energijskoga drva te time pove}anju godi{njega
etata na 9,5 mil. m3, a da se 40 % etata izra|uje sortimentnom metodom uz ve}u uporabu harvestera.
Þ »Mogu}i« se scenarij temelji na primjeni isklju~ivo sortimentne metode izrade drva i pove}anju koli~ine
drva iz proreda, {to }e rezultirati godi{njim etatom od 15 milijuna m3 (od ~ega bi 40 % etata trebalo biti iz
proreda, odnosno 7,2 mil. m3 energijskoga drva).
Proizvodnost strojeva s kojom su ra|ene procjene dobivena je iz raznih statisti~kih podataka te iz podataka koje
su ustupila {umarska poduze}a iz Rusije i Finske (slika 3).
U tablici 1 prikazane su potrebe za {umskim strojevima prema svim trima predlo`enim scenarijima. Najve}i
mogu}i broj strojeva za rad pri sortimentnoj metodi izrade drva procjenjuje se na 400 forvardera te isto toliko harvestera i kamionskih skupova za prijevoz drva, te dodatno po 250 komada pokretnih ivera~a, forvardera i kamiona
za privla~enje i prijevoz drvnoga ostatka.
Tablica 2 tako|er prikazuje potrebu za {umskim strojevima prema svim trima predlo`enim scenarijima kada se
uzme u obzir zamjena starih strojeva za rad pri stablovnoj metodi izrade drva s nabavom novih strojeva za primjenu sortimentne metode izrade drva te uz zamjenu strojeva svakih 7 godina.
U tablicama 3 – 5, na temelju procjena iz tablice 1, prikazane su potrebe poduze}a (koncesionara {uma) za {umskom mehanizacijom.
Rezultati pokazuju da je godi{nja potreba za {umskom mehanizacijom u Lenjingradskoj regiji izme|u 20 – 30
komada srednje velikih forvardera, harvestera i kamiona za prijevoz drva. Potreba bi se u budu}nosti mogla pove}ati
na 30 – 40 strojeva godi{nje, ako se sije~e planirani godi{nji etat ili ~ak 50 – 60 strojeva godi{nje ako se intenzivno
provode prorede. U proizvodnji energijskoga drva sada{nja je potreba 4 forvardera, 10 ivera~a i 10 kamiona za
prijevoz drvnoga iverja. Kada bi se izvr{io planirani etat i kada bi se provodile intenzivne prorede, potreba za
strojevima iznosila bi 30 – 40 strojeva godi{nje.
Od pribli`no tisu}u poduze}a, koja se bave poslovima u {umarstvu, samo njih stotinu imaju koncesiju na {umama
te dovoljno sredstava za nabavu nove mehanizacije i primjenu sortimentne metode. Samo tre}ina koncesionara ima
mogu}nosti za potpunu primjenu sortimentne metode izrade drva. Njihova je potreba prema »trenutnom«
scenariju 270 strojeva: 90 harvestera, 100 forvardera, 80 kamiona za prijevoz drva. Samo se 37 poduze}a bavi proizvodnjom energijskoga drva i imaju potrebu za 50 ivera~a, 50 forvardera i 60 kamiona za prijevoz drvnoga iverja.
Prema »dopustivom« scenariju 60 % koncesionara {uma ima dovoljnu povr{inu {uma i u mogu}nosti je potpuno primijeniti sortimentnu metodu izrade drva. Njihova potreba za {umskim strojevima ogledala bi se u 160 harve-
Croat. j. for. eng. 33(2012)1
59
Y. Gerasimov and T. Karjalainen
Estimation of Machinery Market Size for Industrial and Energy Wood ... (49–60)
stera, 190 forvardera i 150 kamiona za prijevoz drva. Ukupno 56 poduze}a koja se bave proizvodnjom energijskoga
drva imalo bi potrebu za 100 ivera~a, 100 forvardera i 110 kamiona za prijevoz drvnoga iverja.
Prema »mogu}em« scenariju 60 % koncesionara {uma, uz dovoljnu povr{inu {uma i potpunu primjenu sortimentne metode izrade drva, imalo bi potrebu za 260 harvestera, 280 forvardera i 230 kamiona za prijevoz drva. Broj
poduze}a koja se bave proizvodnjom energijskoga drva pove}ao bi se na 70, a imali bi potrebu za 150 ivera~a, 150
forvardera i 180 kamiona za prijevoz drvnoga iverja.
Ekonomski pokazatelji u tehnolo{kom razvoju pridobivanja drva pokazuju pozitivne rezultate kako se od 2005.
godine sve vi{e obnavlja {umska mehanizacija u Rusiji. Iz toga se zaklju~uje da se metode opisane u radu mogu
koristiti kao podloga za razvoj nabavnih strategija i programa {umske mehanizacije i u Lenjingradskoj regiji i u ostatku Rusije.
Klju~ne rije~i: Rusija, industrijsko drvo, energijsko drvo, harvester, forvarder, kamion, pokretni ivera~
Authors' address – Adresa autorâ:
Received (Primljeno): July 21, 2011
Accepted (Prihva}eno): January 09, 2012
60
Yuri Gerasimov, PhD.
e-mail: yuri.gerasimov@metla.fi
Prof. Timo Karjalainen, PhD.
e-mail: timo.karjalainen@metla.fi
Joensuu Research Centre
Finnish Forest Research Institute
Yliopistokatu 6
Box 68
FIN-80101 Joensuu
FINLAND
Croat. j. for. eng. 33(2012)1
Original scientific paper – Izvorni znanstveni rad
Productivity Models for Operational
Planning of Timber Forwarding in Croatia
Igor Stanki}, Tomislav Por{insky, @eljko Toma{i}, Ivica Tonkovi}, Marko Frnti}
Abstract – Nacrtak
In the area of Croatian lowland forests, forwarders are usually used for extraction of timber
assortments. Within the project »Systematization of norms for the production of timber
assortments«, which was financed by the state company »Hrvatske {ume« d.o.o. (»Croatian
Forests«), the process of development and implementation of new productivity norms for
forwarders was carried out.
Initially, for the execution of the research, it was necessary to gather data about technical
characteristics of forwarders most frequently used in Croatia, but also around the world. The
morphological analysis was performed and it was the basis for the classification of forwarders
into classes. Three classes of forwarders were obtained after cluster analysis and load capacity
appeared to be the most important factor. Machine performance was evaluated on 30 research
sites. The standard method of time study (snap-back chronometric technique) was used.
During the recording process, data of factors influencing forwarding (stand and terrain conditions) were collected.
After analyzing the collected data, it was determined that the forwarding productivity depends on the forwarder class, average extraction distance, load characteristics, terrain and
stand conditions. Regression analysis was used for identifying the time consumption of individual work components, and the productivity model for forwarding was developed.
The obtained model was implemented into the application HsPPI. This is a part of the information system developed by IT Department of the state enterprise »Hrvatske {ume« d.o.o.
and is used for production planning in timber harvesting. The system is based on dBase IV
databases and two main program modules. The main parts of the system are: tree marking
data, assortment structure plan, production plan (felling, processing and extraction) and
sales plan. Within a part of the production plan there is a module for calculating productivity norms for timber forwarding.
Keywords: forwarder; productivity norms; planning; lowland forests, Croatia
1. Introduction – Uvod
In the Republic of Croatia, state forests and forestland cover an area of 2,106,917 ha and most of them
(96%) are managed by the state enterprise »Hrvatske
{ume« d.o.o. (»Croatian Forests«; H[; Anon 2006).
From the economic aspect, selection and even-aged
forests are the most significant forests of high silvicultural form. In the Republic of Croatia timber extraction is mainly mechanized, while felling and processing is motor-manual and carried out by chainsaws
(Bojanin and Krpan 1997). In Croatian mountainous
selection forests, skidders are used for timber extraction (Sabo and Por{insky 2005). On the other hand,
in cases of even-aged forests in hilly and lowland
Croat. j. for. eng. 33(2012)1
areas, depending on the stand and terrain conditions,
skidders and forwarders are used for timber extraction, while the use of adapted farming tractors and
tractor assemblies has decreased (Krpan 1996; Beuk
et al. 2007). The lowland area of forests and forestland owned by the state amounts to something more
than 322 thousand ha (Pentek et al. 2011). The lowland forests are of particular importance for this research, as forwarders are mainly used in this part of
Croatia. Lowland forests consist of forest stands of the
pedunculate oak (Quercus robur L.), narrow-leaved ash
(Fraxinus angustifolia Vahl.), black alder (Alnus glutinosa [L.] Gaertn.), willows (Salix sp.), poplars (Populus
alba L., Populus x euramericana clones) and common
hornbeam (Carpinus betulus L.). Annual removal
61
I. Stanki} et al.
Productivity Models for Operational Planning of Timber Forwarding in Croatia (61–78)
amounts to more than 1 mill m³ of wood (Anon
2011). The figures might not be impressive; however,
wood from these forests (pedunculate oak) has been
achieving high prices on the roundwood market,
which is where the importance of the lowland forests
can be seen at its best. The aim of this research is to
establish the system of planning timber extraction
from late thinning and shelterwood felling of lowland forests in Croatia.
2. Problematics – Problematika
Forwarders are self-propelled vehicles intended
for the transport of trees and their parts loaded in the
vehicle bunk area (ISO 2009). The development of
the first forwarder started in Sweden around 1950s,
and their use in Croatia started in 1971 (Slabak 1983).
Forwarders were originally used in cut-to-length timber harvesting, where the felling of trees was performed by harvester, and extracting by forwarder. In
Croatian forestry forwarders are mostly used in lowland forests, particularly for the extraction of timber
from shelterwood felling and late thinning (Por{insky 2002). Therefore, for investigating forwarders’
performance in Croatia, the lowland forests are the
most significant as they cover almost 25% of the total
area covered with high forests (Krpan 1996). Secondary (technical) productivity in forestry is significant
for the research of forest operations (Löffler 1989).
From a scientific point of view, the research of forest
operations includes the study of timber harvesting,
ergonomics, mechanization, construction, economic
aspect and planning of operations, all within the
framework of a sustainable forestry development
(Samset 1992). The research of forestry operations,
and hence also timber forwarding, is based on time
study and on monitoring the influencing (quality and
quantity) factors, data analysis, and mathematical
modeling of time consumption of individual components of the working process (Samset 1990). Similarly as other forms of timber extraction, forwarding
also has the characteristics of a cyclic working process.
Forwarder efficiency is affected by numerous factors. The most important factors influencing the efficiency of timber forwarding is the travel distance
(Sever 1988). With the increase of the travel distance,
the impact of the load volume on the vehicle productivity is also increased (Raymond 1989). Apart
from the forwarding distance, productivity is also
affected by the average assortment volume (number
of pieces in the load) and quantity of timber on a felling site, which is more pronounced in thinning stands
(Tufts and Brinker 1993; Tufts 1997). The highest
share of time consumption in forwarder operations
is related to the so-called terminal times, and namely
loading and unloading of timber (Minette et al. 2004).
62
Optimization of load volume and forwarding distance, and giving preference to downhill forwarding
are the key factors for improving the productivity of
forwarders (Tiernan et al. 2004). Terrain slope higher
than 30% considerably decreases the productivity of
forwarders because on such terrains vehicle mobility is limited (Zimbalatti and Proto 2010). Terrain
classification aimed at determining the optimum
machine for timber extraction shows that in hilly-mountainous area, too, the share of timber forwarding is quite considerable (Miheli~ and Kr~ 2008; Pentek et al. 2008). On steep terrain, up to 60%, it is
possible to use forwarders with winch, the so-called
cable forwarders (Kühmaier and Stampfer 2010). The
use of semi-tracks in conditions of limited soil bearing strength increases fuel consumption but provides vehicle mobility (Wästerlund et al. 2011). Apart
from travel distance, load volume and terrain conditions, forwarder productivity is also affected by the
type of felling, length and type of assortment, driver’s skill and knowledge, as well as characteristics
of hydraulic crane and vehicle load space (White
2004). The increase of the average assortment volume and terrain slope in travel direction (downhill
forwarding) result in the decrease of time consumption (Ghaffarian et al. 2006). The density of secondary forest roads (forest trails) also affects the forwarding productivity (Mederski 2006). Up to date
planning methods, i.e. spatial optimization of working
cycle shifts based on data on quantity and locations
of assortments and possible travel areas of the felling
site also increase the timber forwarding productivity
(Flisberg et al. 2007). Comparative research of skidding/forwarding machines carried out in stands of
small coniferous trees showed that, in terms of costs,
figures speak in favour of timber forwarding, as
forwarder productivity is twice higher than the productivity of the skidder with winch (Li et al. 2006).
Forwarder efficiency depends on the type of the
vehicle used, i.e. on its nominal carrying capacity, as
forwarders of higher carrying capacity achieve lower costs and higher productivity per product unit
(Jirou{ek et al. 2007). Nowadays forwarders are not
conceptually different from those of half a century
ago, but they have made serious progress in terms of
environmental soundness, ergonomics and steering
automation (Pandur et al. 2009). One of the ways to
increase productivity is the use of dynamic system
for changing the volume of the bunk area (Brunberg
1999), i.e. its height and width (Brunberg 2001). Attaching the trailer with the loading space behind the
rear end of the standard forwarder may increase the
system productivity (Lindroos and Wasterlund 2011).
Investigations were performed of the use of »flats«
or »swop bodies«, where timber is not unloaded
Croat. j. for. eng. 33(2012)1
Productivity Models for Operational Planning of Timber Forwarding in Croatia (61–78)
from the forwarder nor loaded into the truck, as they
are used with both kinds of transport, thus increasing productivity and simplifying primary transport
of timber, but with increased costs (Freitag and Warkotsch 2011). Considering the productivity and costs
of timber harvesting machines at an annual level, the
share of the travel of machines between felling units
is quite considerable, so when planning, the possibility of leasing trucks for the transport of machines
should be taken into account (Väätäinen et al. 2006).
Productivity of timber forwarding is higher than
the productivity of timber skidding in lowland forests of Croatia, and the increase depends on stand
and terrain conditions and ranges between 28 and
126% (Bojanin and Krpan 1994). The operation of
forwarders in Croatia, unlike the Scandinavian assortment method (CTL), makes no use of felling and
processing machines. This is the effect of natural
factors (natural forests, trees of large size, considerable share of broadleaved trees, etc.), but also of
tradition (Bojanin and Krpan 1997). The above said
is the cause of a different approach to gathering and
processing data, selecting the influencing factors and
modelling the working process. One of the problems
arising is the definition and determination of the
mean distance of timber forwarding. Some authors
consider that the distance of timber forwarding is
the distance between the roadside landing and the
point in the felling site when the bunk area is half
loaded with timber (Kuitto et al. 1994; Nurminen et
al. 2006). Accordingly, the mean distance of timber
forwarding would be equal to the sum of travel
distance of unloaded vehicle and half the travel in
timber loading i.e. the travel between the loading
points (Suvinen 2006; Väkevä et al. 2001). When
investigating forwarders in Croatian lowland forests,
the distance of timber forwarding was considered to
be the arithmetic mean of the sum of distances tra-
I. Stanki} et al.
velled by fully loaded and unloaded forwarder, while
the time consumption of the vehicle movement during loading process was defined depending on felling density, i.e. net timber volume per hectare (Por{insky 2002, 2005; Stanki} 2010).
The production of timber assortments has been
supported by information systems used by the state
company H[ for monitoring and recording the production of timber assortments. The information system has been continuously developing for twenty
years, since the founding of the company, and it is the
result of the development program of the company’s
IT Department. At the beginning of the development, the system was based on personal computers
with programs made in computer language FoxPro
2.6 for DOS (dBase IV as database). Although the
computerization of the company has gone a long
way from those times, a part of these programs and
FoxPro2.6 as program language are still being used,
while new programs are being developed for Windows operating systems in Visual FoxPro 9.0 and
on.NET platform with MS SQL database.
A part of the information system of the company
H[ is the production subsystem, by which all timber
harvesting processes are monitored – from production planning to issuing bills to buyers. HsPPI and
HsPro are important parts of this subsystem. HsPPI
refers to the production planning, while HsPro refers
to the monitoring of timber assortments production.
The basis of the information flow is in the forest
database HsFond that basically represents digitalized Management Plan Prescriptions. One of the factors is the Harvesting Plan, which represents the
beginning of the production planning. On that basis,
the harvesting (sub)compartment is selected, tree
marking data is prepared, distribution of marked
trees is entered, harvest is planned out, cut block is
established, the technology of timber processing is
chosen along with the production plans, where the
felling and processing norms, as well as the primary
transport, have to be determined. At the end of the
planning process, the sales plan is developed. All
these processes are carried out within the HsPPI
application that H[ uses for the preparation of production within harvesting.
3. Materials and methods – Materijal i
metode
3.1 Classification of forwarders – Razredba
forvardera
Fig. 1 Forwarding in Croatian lowland forests
Slika 1. Izvo`enje drva u hrvatskim nizinskim {umama
Croat. j. for. eng. 33(2012)1
A good knowledge of forwarders as means of
work in the forestry production is of crucial significance. Many research methods are already known,
63
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Productivity Models for Operational Planning of Timber Forwarding in Croatia (61–78)
Table 1 Some technical features of investigated forwarders
Tablica 1. Neke tehni~ke zna~ajke istra`ivanih forvardera
Forwarder type
Tip forvardera
Number of wheels
Broj kota~a
Engine power
Snaga motora
Length
Duljina
Width
[irina
Height
Visina
Mass
Masa
Payload
Nosivost
Crane reach
Dohvat dizalice
n
kW
mm
mm
mm
kg
kg
m
Timberjack 1210
6
114
9,060
2,640
3,710
11,720
12,000
10.3
Timberjack 1410B
8
9,205
2,705
3,700
16,500
14,000
8.5
Timberjack 1710B
Valmet 840
6
129
156.5
10,450
3,010
3,900
17,400
17,000
7.2
6
124
9,007
2,650
3,780
13,800
12,000
9.2
Valmet 860
6
140
9,170
2,740
3,789
14,300
14,000
9.2
from those that determine borderline usability, to
those that study the historical development of its
construction. One of the studying methods for the
machines used in forestry is the morphological analysis based on the selected geometrical, mass and
other factors, on which basis dependencies are calculated and opinion on validity of machine selection
is made (Por{insky 1997). One of the first morphological analyses of off-road vehicles was carried out by
Bekker in 1956 (Sever 1980). Gradually, the method
was accepted and is used even today for the evaluation of forestry machines or tools, especially by researchers from Department of forest engineering of
the Forestry Faculty Zagreb for investigation of chippers ([u{njar 1998), farming tractors (Horvat and
[u{njar 2001), skidders (Horvat et al. 2007), hydraulic cranes ([u{njar et al. 2007), chainsaws (Por{insky
et al. 2008), farmer winches ([u{njar and Bori} 2008).
In the Croatian forestry, the following forwarders
are used most frequently: Timberjack 1210, Timberjack 1410, Timberjack 1710, Valmet 840 and Valmet
860 (Table 1). Modeling of productivity individually
for each forwarder would be cost-ineffective, so it
was necessary to group them in classes and analyze
them on that basis. Many forwarder classifications
are already known, and according to them forwarders are classified by net mass, load capacity or gross
mass (vehicle + load, (Por{insky 1997)). The latest
forwarder classification found in literature is made
based on their loading capacity (payload) to light
(<10 t), medium (10 t – 14 t) and heavy forwarders
with the load capacity over 14 t (Brunberg 2004). In
this case, the morphological analysis of forwarder
families according to their numerical values (dimensions, mass, load capacity, etc.) will be used as a basis
for grouping vehicles in classes. The data have taken
from the obtained and adapted database, only for
the vehicles of the new generation (Lugmayr et al.
2009).
64
3.2 Assortments characteristics – Zna~ajke
sortimenata
The Croatian lowland forests are characterized
by a great variety of stand conditions. There is a
wide range of tree species, from willows and poplars, over black alder and narrow-leaved ash, to
pedunculate oak and common hornbeam. The area
is characteristic by the assortment method of processing, with forwarding as a special way of timber
extraction. The assortment volume is important for
obtaining the correct figures of the mean load volume that impact the forwarder productivity. The aim
was to obtain the mean assortment dimension, so it
was formed on the basis of trees taken from the tree
marking data, that is by connecting the data from
two applications of the information production subsystem HsPPI and HsPro. Data on trees marked to be
felled and data on processed timber assortments in
the work yards were collected for the yards where
the extraction has been carried out with forwarders
over the last couple of years (Fig. 2). Data on tree
species whose share in the lowlands is low (fruit
trees, common maple, lowland elm, walnut, etc.)
were left out from the analysis, as well as cutting
blocks with small number of samples. Only the data
for the most important species, based on their share
in the prescribed removal of the Croatian lowland
forests, were taken into analysis: pedunculate oak,
common hornbeam, narrow-leaved ash and black
alder. The goal of the analysis is to determine the
mean assortment volume, mean diameter and length
from the volume of marked tree by the tree species.
The stated is necessary to determine the productivity
of forwarders in this system of harvesting.
3.3 Forwarder productivity – Proizvodnost
forvardera
The research of forwarder productivity was carried out in the area of Croatian lowland forests (Fig.
2). In this research, the term Object of Study (OS) is
Croat. j. for. eng. 33(2012)1
Productivity Models for Operational Planning of Timber Forwarding in Croatia (61–78)
I. Stanki} et al.
Fig. 2 Research sites of forwarder productivity and timber assortments characteristics
Slika 2. Mjesta istra`ivanja proizvodnosti forvardera i zna~ajki sortimenata
used, which refers to individual stand, that is the
compartment/subcompartment where harvesting is
carried out. Raw data for productivity analysis were
taken from the previous investigations of a total of 30
objects; 5 OS (Por{insky 2000) + 3 OS (Por{insky 2005)
+ 22 OS (Stanki} 2010). Average removal per OS was
199.79 m3/ha, average tree size was 3.22 m3/tree and
average area of OS was 27.70 ha.
The research of the machine work is based on the
time and work study. The basis is the work and time
study, division of work process or work phase into
consisting parts of the shortest possible time duration that can still be measured precisely enough.
Contemporary approach to time study presupposes
the implementation of analytical measuring methods,
whereby work process is divided under particular
schemes into work components with the goal of
synthesis during data and results processing.
Extraction of timber by forwarders has the characteristics of cyclic work. Each cycle (turn) consists
of four main cyclic work components (unloaded traveling, timber loading, loaded traveling and unloading of timber), plus work pauses or time consumptions whose character is not cyclic, but periodic.
Forwarder productivity is modeled by the following module:
Croat. j. for. eng. 33(2012)1
ìï
t = fa í sof
ïî
ü
æ 60 60 ö
æ
ö
÷ + son × ç 60 + 60 ÷ + tl + tu ïý é min ù
× çç +
÷
ç
÷
ïþ êë turn úû
è v1 v2 ø
è v3 v4 ø
P=
60 × Vl ém 3 ù
ê ú
t ë h û
where:
t – total time, min/turn
sof – forwarding distance (offroad), km
v1 – unloaded vehicle speed (offroad), km/h
v2 – loaded vehicle speed (offroad), km/h
son – forwarding distance (forest road), km
v3 – unloaded vehicle speed (forest road), km/h
v4 – loaded vehicle speed (forest road), km/h
tl – loading time, min/turn (tl=tl1+tl2)
tu – unloading time, min/turn (tu=tu1+tu2)
fa – additional time factor
Vl – load volume, m3/turn
P – productivity, m3/h
The study of forwarder work time was carried
out by snapback method, using manual digital chronometer. Besides the time study, data were collected
of all factors influencing the work process. Forwarding distance was measured by hand GPS devices. In
order to establish the forwarder performance, loaded
65
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Productivity Models for Operational Planning of Timber Forwarding in Croatia (61–78)
Table 2 Correlation table of studied values (those bold are significant at p < 0.05)
Tablica 2. Korelacijska tablica prou~avanih vrijednosti (podebljane su signifikantne za p < 0,05)
Characteristics
Zna~ajke
Means
Std. Dev.
Artimeti~ke Standardne
sredine
devijacije
Engine
power
Snaga
motora
Length
Duljina
Width
[irina
Height
Visina
Clearance
Odignutost
vozila od
podloge
Mass
Masa
Payload
Nosivost
Crane
reach
Doseg
dizalice
Lifting moment
(gross)
Bruto podizni
moment
dizalice
Engine power, kW
Snaga motora, kW
138.24
28.51
1.00
0.60
0.72
0.53
0.53
0.82
0.81
0.08
0.79
Length, mm
Duljina, mm
9,314.38
874.15
0.60
1.00
0.63
0.32
0.60
0.66
0.67
–0.02
0.67
Width, mm
[irina, mm
2,716.63
170.42
0.72
0.63
1.00
0.59
0.47
0.80
0.84
0.12
0.82
Height, mm
Visina, mm
3,710.45
133.33
0.53
0.32
0.59
1.00
0.34
0.64
0.65
0.35
0.70
Clearance, mm
Odignutost vozila od
podloge, mm
637.36
57.64
0.53
0.60
0.47
0.34
1.00
0.58
0.60
–0.08
0.61
Mass, kg
Masa, kg
15,183.75 3,038.63
0.82
0.66
0.80
0.64
0.58
1.00
0.85
0.11
0.84
Payload, kg
Nosivost, kg
12,672.46 2,702.39
0.81
0.67
0.84
0.65
0.60
0.85
1.00
0.12
0.89
Crane reach, m
Doseg dizalice, m
Lifting moment
(gross), kN
Bruto podizni
moment dizalice, kN
8.88
1.21
0.08
–0.02
0.12
0.35
–0.08
0.11
0.12
1.00
0.27
107.10
24.42
0.79
0.67
0.82
0.70
0.61
0.84
0.89
0.27
1.00
assortments were counted and the number of the
identification plastic tag was recorded in case of
large sawtimber and veneer assortments. In other
cases (with small assortments – pulpwood and long
firewood), direct measurement of processed assortments took place, whereby data on tree species, mean
diameter and length were entered into a corresponding form. The ground bearing capacity was determined for each individual cycle, by visual estimate
of the recorder. The soil bearing capacity was studied in line with the modified classification of ground
bearing capacity that was already used in similar
form within the research of machine performance in
areas of the Croatian lowland forests (Por{insky 2000).
Under this classification, forest soils were classified
into the following load-bearing groups, and it was
applied in further analyses:
Þ Soil of good load-bearing capacity – firm and
moderately firm soil. It includes dry, frozen or
occasionally wet soil which presents no problems
for moving vehicles. By a single pass of the vehicle, the tracks depth amounts to less than 5 cm,
66
and by multiple passes the depth amounts up to
25 cm, maximum 30 cm. When walking on such
soil, shoe soles are dry or humid.
Þ Soil of limited load-bearing capacity – soft and
very soft soil. It is a soil that is partly to fully
saturated with water. Walking on it is difficult,
tracks of shoes are fully visible. Sinking of vehicles into the ground and slipping of wheels are
appeared, vehicle speed is reduced, and after a
single pass, the mineral layer of the soil can be
exposed. Implementation of semi-tracks on the
rear wheels of bogie axle and chains on the front
wheels of single axle is recommended to obligatory (in extremely unfavorable conditions).
Before starting the recording, an online form for
the input of recorded data was developed. The form
was developed using.NET technology and it could
be found at the address http://norme.hrsume.hr. At
the end of the work process recording, each recorder
would register to the stated webpage and enter the
data into the integral database. MSSQL database
was used.
Croat. j. for. eng. 33(2012)1
Productivity Models for Operational Planning of Timber Forwarding in Croatia (61–78)
4. Results of the research – Rezultati
istra`ivanja
4.1 Forwarder classification – Razredba
forvardera
Forwarder analysis was carried out in the program package Statistica 08. In this analysis, the following vehicle morphological values were used:
length, width, height to the cab roof, clearance of the
vehicle from the ground, mass, payload, reach and
lifting moment of the hydraulic crane. For the values
whose data were not available in the established
database, substitution was made with the value of
the arithmetic mean of that variable. Database contains variables for 56 forwarders. Through a thorough
consideration of the effect of available data on morphological characteristics of vehicles, the connection
of the vehicle mass with most other values is evident
(Table 2), which is logical due to the fact that the
existence of mass determines the occurrence of other
features. Vehicle mass is mostly correlated to the
power of the engine and to payload and it is the key
parameter, on which all other forwarder characteristics, except the hydraulic crane reach, are dependent. If the mass value increases, all other vehicle
characteristics increase, too.
Payload (PL, load capacity) is one of the most
important exploitation characteristics of forwarders.
By reviewing the vehicles’ technical characteristics
database it can be determined that mass and load
capacity of forwarders are approximately the same.
The highest correlation to other values is indicated
precisely by the PL of the vehicle (Table 2). For this
reason, PL was used for the classification of forwarders.
The k-mean algorithm was used for grouping of
forwarders. This algorithm assigns each item to the
group whose centroid is closest to it. Centroid is a
point created by calculating the arithmetic mean for
each dimension, separately for each item in the
group. By implementing the mentioned algorithm,
grouping of data into groups based on PL was made.
The first group includes forwarders whose PL is
closest to the centroid of 9,929 kg. The second group
includes those whose PL is closest to the centroid
value of 12,125 kg, while the third group is formed
by forwarders whose PL is closest to the value of
15,571 kg. Distribution of variables, payload and
other technical features according to forwarder class
are shown in Fig. 3.
Through further analysis for the needs of operative classification of forwarders, rough borderlines
can be set among three forwarder classes by their PL,
and those are: 11,000 kg and 14,000 kg. The first class
Croat. j. for. eng. 33(2012)1
I. Stanki} et al.
consists of vehicles whose PL is less than 11,000 kg,
the second of those whose PL amounts from 11,000
to 14,000 kg, while the third class consists of forwarders whose PL is above 14,000 kg.
As it is obvious that the increase of PL in the
forwarder family results in the increase of other studied dimensions, it can be concluded that there are
three forwarder classes – light, medium and heavy
forwarders. In line with the performed classification
it can be determined that light forwarders are not
used in the Croatian forestry. Therefore further research will be focused on the medium and heavy
forwarders. Timberjack 1210 and Valmet 840 fall into
the class of medium forwarders, whereas Timberjack
1410, Timberjack 1710 and Valmet 860 are in the class
of heavy forwarders.
4.2 Characteristics of assortments and vehicle
load – Zna~ajke sortimenata i tovara
forvardera
In order to gain insight into the load characteristics (mean volume and mean diameter), data
from 1532 working sites were analysed, where timber extraction was carried out by forwarders over
the last few years (since the beginning of full implementation of information production subsystem
HsPPI and HsPro). Work sites were situated in the
area of the Croatian lowland forests, and they
are characterized by motor-manual felling and assortment method of timber processing along with
the timber extraction by forwarders. Each point in
Fig. 4 represents average value for individual felling
site.
Two groups of assortment size can be detected
(Fig. 4). The first group is formed by the classes of
large assortments of bigger dimensions – veneer logs,
sawlogs (1st, 2nd and 3rd class) and logs for peeling.
The second group includes small assortments, usually of smaller dimensions – long firewood, mining
wood and thin industrial roundwood. Both assortment groups show a large dissipation of raw data,
which is a consequence of buck-to-quality (BTQ)
and assortment method of timber processing.
Dependence of the number of loaded assortments
on the decrease of soil bearing capacity has been
determined (Fig. 5). By decrease of soil bearing
capacity, the number of loaded roundwood assortments is reduced as well. In some cases, the overload
of forwarder was noticed in conditions of limited
soil bearing capacity, aimed at increasing productivity in spite of the decrease of vehicle speed. This can
be explained by the subjective influence of some
forwarder operators and their overloading of the
vehicle in unfavourable conditions, all with the goal
of increasing the work efficiency. Reduction of load-
67
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Productivity Models for Operational Planning of Timber Forwarding in Croatia (61–78)
Fig. 3 Some technical features according to forwarder class
Slika 3. Neke tehni~ke zna~ajke pojedinih razreda forvardera
68
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Productivity Models for Operational Planning of Timber Forwarding in Croatia (61–78)
I. Stanki} et al.
Fig. 4 Characteristics of roundwood from Croatian lowland forests
Slika 4. Zna~ajke oblovine iz hrvatskih nizinskih {uma
Fig. 5 Number of roundwood pieces in the bunk area of forwarder
Slika 5. Broj komada oblovine u tovarnom prostoru forvardera
ed assortments in conditions of reduced soil bearing
capacity was more expressed with the large than
with the medium size forwarders.
The analysis that was carried out, i.e. the modelling of the mean assortment volume, is the input
Croat. j. for. eng. 33(2012)1
indicator for determining further load characteristics.
One of the most important parameters is also the
number of loaded assortments (Fig. 5). The product of
mean assortment volume and number of assortments
gives the load volume (Vl = Va × n).
69
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Productivity Models for Operational Planning of Timber Forwarding in Croatia (61–78)
4.3 Modeling of the forwarder productivity
Oblikovanje proizvodnosti forvardera
The forwarding productivity was studied using
the time study on totally 1440 recorded work cycles,
out of which 651 cycles were performed with medium, and 789 with heavy forwarders.
4.3.1 Time consumption of loaded and unloaded
vehicle travel – Utro{ak vremena vo`nji
optere}enoga i neoptere}enoga vozila
Based on the dependence of time on the travel
distance, the average speed of (un)loaded forwarders on forest road and off-road was calculated. The
assumption was that forwarders move at uniform
speed (Fig. 6). Medium size forwarders have a better
mobility in the conditions of limited soil bearing
capacity than heavy forwarders when they are
unloaded. This is not the case in the conditions of
good soil bearing capacity where heavy forwarders
reach higher speeds. Larger differences in the vehicle
speeds on the forest road between the forwarder
classes are caused by bigger variety of conditions on
the monitored sites in the areas of roadside landings.
Based on the modeled driving speeds (arithmetic
means of recorded speeds per turn, Fig. 6) of for-
warders and average traveling distances off-road
(sof) and on the forest road (son), time consumption of
a traveling is obtained.
4.3.2 Time consumption of timber loading
Utro{ak vremena utovara drva
Timber loading time covers the time of forwarder’s work in the felling area during loading, and the
characteristic of this variable is that it does not change
with the change of the forwarding distance. Forwarder’s work in the felling area starts with the end
of the unloaded vehicle travel, or in other words, on
the spot of the first loading. After loading the processed assortments within the reach of the hydraulic
crane, the forwarder moves towards the next loading place, and continues doing so until reaching the
optimal load. During timber loading (tl), two significantly different groups of work components can be
detected (tl = tl1 + tl2):
Þ Timber loading with crane (tl1) – the operator
loads the timber into the bunk area using only the
hydraulic crane,
Þ Relocation of forwarder (tl2) – forwarder moves
from one loading area to the other.
Fig. 6 Forwarders’ speed
Slika 6. Brzine kretanja forvardera
70
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I. Stanki} et al.
Fig. 7 Time consumption of timber loading
Slika 7. Utro{ak vremena utovara drva
Time consumption of timber loading by the hydraulic crane is dependent on the forwarder class
and the number of loaded assortments. The recorded
data are equalized by a linear model line from the
source (Fig. 7, left). Timber loading expressed the
influence of the »Volume-Piece Law«, as the smaller
dimensions of the loaded roundwood, the number
of loaded pieces and the crane time consumption
have increased.
Time consumption of forwarder relocation is impacted by the »Production Law«, i.e. by the quantity
of the cut and processed timber per unit of area
(Fig. 7, right). It is reflected in the exponential
increase of time consumption of forwarder relocation due to diminished felling density (thinning) and
vice versa (shelterwood and clear cutting). Relocation time consumption is higher within the group of
heavy than medium forwarders. This is due to the
fact that medium forwarders have larger hydraulic
crane reach than heavy forwarders (Table 1).
4.3.3 Time consumption of timber unloading
Utro{ak vremena istovara drva
When the loaded forwarder ends its travel, its
work starts on the roadside landing aimed at unloading, stacking and sorting of timber. Similar to
the loading, the unloading at the roadside landing
(tu) is additionally divided into two groups of work
components (tu = tu1 + tu2):
Þ Crane work time (tu1, where the operator works
solely with the hydraulic crane with the goal of
unloading the timber), and
Croat. j. for. eng. 33(2012)1
Þ Relocation time during unloading (tu2, where the
forwarder moves from pile to pile with the goal
of separating timber by tree species and quality
classes).
Time consumption of crane unloading depends
on the forwarder class and number of roundwood in
the load. During unloading, the operators classify
the timber according to tree species and quality classes, piling the unloaded timber onto separate stacks.
The regression curve of recorded data is shown in
Fig. 8. The asymptotic model was used. The increase
of time consumption of crane unloading with reference to the increase of number of loaded assortments can be observed. It is decreased with the larger number of loaded assortments of smaller mean
volume. This is explained by the fact that when unloading, the crane grips two or more pieces of roundwood assortments.
The absence of wood classification and relocation
has been noticed on a smaller part of observed research sites. This was conditioned by the stand characteristics (pure stands), silvicultural treatment (type
of cutting), type of processing firewood, quality and
dimensions of assortments and landing space. In the
cases when timber was sorted on the roadside landing,
higher time consumption of this work component
was recorded. Mean time consumption for heavy
forwarders was 0.84 min/turn, whereas for medium
forwarders it amounted to 0.73 min/turn (Fig. 8,
right). This phenomenon can be explained with the
higher initial acceleration of medium forwarders.
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Productivity Models for Operational Planning of Timber Forwarding in Croatia (61–78)
Fig. 8 Time consumption of timber unloading
Slika 8. Utro{ak vremena istovara drva
The sorting of assortments at the roadside landing
has affected the decrease of forwarder efficiency in
relation to its efficiency when not performing the
timber separation when unloading. By the increase
of forwarding distance, the negative effect of timber
separation on forwarding efficiency is diminished,
due to the growth of vehicle relocating share in the
total cycle time.
4.3.4 Delays (downtime) and additional time
factors – Prekidi rada i faktori dodatnoga
vremena
Delays consist of unavoidable and avoidable of
work times. Various technological and organizational measures are taken to try and reduce it to the
necessary level. The unavoidable delays are classified as preparatory time, occasional works and breaks.
The avoidable delays include unnecessary conversations among workers, conversations between workers
and passers-by and recorders, and excessive resting
time. Vehicle breakdowns that cannot be eliminated
without the intervention of a mechanic are also included into the avoidable delays. Avoidable and unavoidable delays per turn were taken into analysis together and they are shown in Fig. 9 (left).
The additional time and additional time factor
are determined through the analysis of unavoidable
delays only. It was determined by this study that the
additional time factors vary in a wide range and that
they are higher than in previous studies. The average additional time was determined for each individual OS (Fig. 9, right). The value of the mean
72
additional time factor amounts to 1.33, or 33% of the
effective time. Considering the structure of the additional time, it can be determined that the preparatory
time accounts for 33%, occasional works for 33%,
and personal breaks for 33% of the total unavoidable
delays.
5. Implementation of the model into the
information system – Ugra|ivanje modela
u informacijski sustav
One of the components of production planning
process is the determination of norms for felling and
processing, as well as for timber extraction. The existing norms (official and still in use) are inherited from
times before the company H[ was founded (before
1990), and there are still a couple of regional systems
functioning.
In order to unify the norm system on the level of
the company, »new norms« as a result of work of the
Forestry Faculty Zagreb (project bearer) and H[ (project investor) were created. New norms have been
integrated into the HsPPI program (Fig. 10). Determination of norms starts with the selection of the
management unit (gospodarska jedinica) and type of
yield (vrsta prihoda), followed with the list of the
marked compartments/subcompartments from the
Management Plan with all the data needed for norm
calculation. Those are: type of yield (prihod), silvicultural form (uzgojni oblik) and total area of the compartment/subcompartment (povr{ina). For each compartCroat. j. for. eng. 33(2012)1
Productivity Models for Operational Planning of Timber Forwarding in Croatia (61–78)
I. Stanki} et al.
Fig. 9 Share of delays in relation to effective time and additional time factor
Slika 9. Udjeli prekida rada prema efektivnomu vremenu i faktor dodatnoga vremena
Fig. 10 Screenshot of tab for norm calculation for forwarders in HsPPI
Slika 10. Prikaz zaslona ra~unala pri izra~unu normativa za forvardere u aplikaciji HsPPI
ment/subcompartment from the list there is norm
calculated for individual work phase, and this is
made by selecting tabs: »Felling and Processing«
(sje~a i izrada), »Extraction – Skidders« (privla~enje –
Croat. j. for. eng. 33(2012)1
traktori) or »Extraction – Forwarders« (izvo`enje –
forvarderi).
The first step in the norm calculation process is
the calculation of felling and processing norm, due
73
I. Stanki} et al.
Productivity Models for Operational Planning of Timber Forwarding in Croatia (61–78)
to the fact that by selecting the work method, the final
assortment structure is obtained, for whose extraction
the norm is to be developed. From other data necessary for the development of forwarding norms, a part
is taken from the Felling Plan (main tree species –
glavna vrsta; volume of mean stand tree – SKS; net
marked wood volume per unit of area – neto dozna~eno), while other parameters are entered (Fig. 10):
machine type (tip stroja),
equipped with semi-tracks (upotreba polugusjenica),
soil-bearing capacity (nosivost tla),
mean off-road forwarding distance (srednja udaljenost kretanja vozila po bespu}u),
Þ mean forwarding distance on roadside landing
(srednja udaljenost kretanja vozila po pomo}nom stovari{tu).
Output data are norms for large (tehnika) and
small assortments (TO i VM) per hour and per workday (8 hours) for selected work conditions.
Through a thorough analysis carried out by forestry experts it was established that the productivity model presented in this study plans higher
norms and decreased delay times than the existing
ones (Tomi} 2007).
Þ
Þ
Þ
Þ
6. Conclusions – Zaklju~ci
This research covered the analysis of the factors
impacting forwarding, as a special aspect of primary
transport of timber in the lowland forests of the
Republic of Croatia. It is characteristic of timber
harvesting systems in the area that felling is performed motor-manually and timber is processed by
power chainsaws, timber is bucked according to its
quality, and extraction of timber to roadside landings is fully mechanized. The method used is not the
traditional cut-to-length (CTL), but buck-to-quality
(BTQ) method.
Aiming to develop an operationally implementable system of timber forwarding planning, forwarders were classified according to their technical characteristics. The most important factor appeared to
be the payload, so this variable was used for clustering the vehicle types. Three classes of forwarders
were determined: light, medium and heavy forwarders. Light forwarders have a load capacity of up to
11,000 kg, medium from 11,000 kg to 14,000 kg, and
heavy forwarders above 14,000 kg. Light forwarders
are not used in the Croatian forestry, and farm tractors with semi-trailers equipped with winch and
hydraulic crane are used instead.
Loaded roundwood features were determined
with the goal of calculating productivity (norm projection) by modeling the volume of large and small
74
assortments from an average marked tree volume
for all species represented in the lowland forests. The
data were gathered by joining together two information subsystems HsPro and HsPPI. By the increase
of marked tree volume, the average volume of large
assortments grows exponentially, whereas with small
assortments, after the initial growth, the relations
take values closer to the asymptote of the curve
(0.34 m3/pcs).
The results of the forwarding productivity study
are under a strong influence of the interaction of
important factors prevailing in the Croatian lowland
forests, and the study came to the following conclusions:
Þ The forwarder class influences the level of forwarder productivity, and it does so primarily
through its payload, or load volume, but also
through its speed and time consumption during
loading and unloading.
Þ Diminished levels of timber extraction by forwarders are influenced by conditions of off-road
soil-bearing capacities as a result of the increase
of time consumption of forwarding, i.e. lower
speed and lower load volume.
Þ The use of semi-tracks, which provide the mobility of forwarders in unfavorable conditions, additionally lower the speed, increasing the time
consumption of forwarding.
Þ The increase of forwarding distances diminishes
forwarder’s productivity, as the share of the time
spent moving grows within the structure of the
total time consumption of the work shift. However, the influence of distance on the forwarding
productivity should be viewed through its interaction with the classes of soil-bearing capacity
and classes of forwarders. Likewise, with the increase of forwarding distance, the load volume
becomes more significant.
Þ Stand conditions and forest management guidelines demonstrated the impact on the productivity of timber forwarding through the well known
Laws of Mechanizing Forest Works, i.e. through felling density (Productivity Law), features and dimensions of processed roundwood (Volume-Piece
Law and Product Type Law).
Based on the obtained research results and requests
of the company H[, a model of forwarder productivity for lowland forests was established and finally incorporated into the production information subsystem. Real data from the first planning stage (forest
inventory data, tree marking plan, assortment structure plan, etc.) and developed forwarder productivity
model, together with input work parameters ensures
the objectivity of norms used in timber forwarding.
Croat. j. for. eng. 33(2012)1
Productivity Models for Operational Planning of Timber Forwarding in Croatia (61–78)
Acknowledgements – Zahvala
The research was conducted with the support of
the company »Hrvatske {ume« d.o.o. that provided
the financial support and insured the material and
human resources for the execution of the project
»Systematization of Norms for the Production of Timber
Assortments – Norms for Forwarding«. The project
bearer was the Faculty of Forestry of the University
of Zagreb.
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Sa`etak
Modeli proizvodnosti pri operativnom planiranju izvo`enja drva
forvarderima u Hrvatskoj
U podru~ju hrvatskih nizinskih {uma za skupljanje i privla~enje drvnih sortimenata primjenjuje se poseban
oblik primarnoga transporta drva, za koji je znakovita potpuna odignutost tereta (oblovine) od tla, pri ~emu se
koriste forvarderi. Forvarderi su samopogonjena vozila namijenjena pomicanju stabala ili njegovih dijelova koji
drvo izvoze utovareno u tovarnom prostoru vozila iz {umskoga bespu}a do pomo}noga stovari{ta, odnosno {umske
ceste. U sklopu istra`iva~koga projekta »Usustavljenje normi i normativa«, koji financiraju Hrvatske {ume d.o.o.,
razvijene su nove proizvodne norme izvo`enja drva forvarderima.
Proizvodnost izvo`enja drva ovisi o kori{tenom tipu vozila. Stoga je za provedbu istra`ivanja bilo potrebno prikupiti podatke o tehni~kim zna~ajkama novijih forvardera u Republici Hrvatskoj, ali i u svijetu. Potom se pristupilo
morfolo{koj ra{~lambi na osnovi koje su se vozila razvrstala u razrede, jer je neodr`ivo projektirati normu za svaki
tip vozila zasebno. Klasterskom analizom dobivena su tri razreda forvardera. To su laki, srednje te{ki i te{ki forvarderi. Kao najva`niji ~imbenik pri razvrstavanju pokazala se nosivost forvardera. Laki su nosivosti do 11 t, srednje
te{ki od 11 do 14, a te{ki forvarderi imaju nosivost ve}u od 14 t. U hrvatskom {umarstvu koriste se uglavnom
srednje te{ki i te{ki forvarderi, dok se umjesto lakih forvardera koriste razne ina~ice traktorskih ekipa`a.
Primjena izvo`enja drva razumijeva sortimentnu metodu izradbe oblovine. Stoga su zna~ajke tovara (prosje~an obujam komada i njegove dimenzije) posredno uvjetovane i prosje~nim dimenzijama dozna~enih stabala za
sje~u i izradbu. Spojeni su podaci iz dviju aplikacija (HsPPI i HsPRO) za ona radili{ta na kojima se od po~etka primjene tih aplikacija izvozilo forvarderima. Na osnovi podataka o doznaci stabala oblikovane su zna~ajke oblovine u
etatu najzastupljenijih vrsta drva.
Informati~ka slu`ba poduze}a Hrvatske {ume d.o.o. preuzela je zadatak izrade sustava za prikupljanje i pohranu snimljenih podataka. Za pohranu se koristila baza podataka MS SQL Server 2000. Kao korisni~ko su~elje za prihvat podataka slu`ila je web-aplikacija zasnovana na dinami~nim mre`nim stranicama koje se u potpunosti izvr{avaju na poslu`iteljskom ra~unalu i izravno komuniciraju s bazom podataka. Sustav je izra|en pomo}u tehnologije
Microsoft ASP.NET, programiran u Visual Basic.NET-u, a izvr{ava se na poslu`itelju Windows Server 2003.
Rad je forvardera istra`en na 22 radili{ta metodama studija rada i vremena, primjenom povratne metode
kronometrije. Radi {to korektnijega oblikovanja utro{aka vremena tim su podacima pridru`eni i podaci prethodnih
istra`ivanja, opsega 8 radili{ta, te je oblikovanje utro{aka vremena rada zasnovano na podacima s ukupno 30 radili{ta. Pri ra{~lambi su upotrijebljeni prikupljeni podaci o sastojinskim i terenskim utjecajnim ~imbenicima izvo`enja drva.
Pri planiranju privla~enja drva, kao najzahtjevnijoj sastavnici pridobivanja drva, postavljaju se zahtjevi za
poznavanjem prisutnih utjecajnih ~imbenika odre|enoga podru~ja te njihova djelovanja na djelotvornost kori{tenih sredstava privla~enja drva. Va`niji utjecajni ~imbenici izvo`enja drva iz sje~ina hrvatskih nizinskih {uma
nastali iz ovoga istra`ivanja svakako su srednja udaljenost privla~enja, nosivost podloge (tla), obujam prosje~noga
komada oblovine u tovaru, sje~na gusto}a te nosivost forvardera. Regresijskom ra{~lambom utvr|ena je ovisnost
trajanja pojedinih sastavnica rada o utjecajnim ~imbenicima te je izra|en model proizvodnosti forvardera.
Po zavr{etku istra`ivanja dobiveni je model prema zahtjevima naru~itelja ugra|en u program HsPPi. Tu je
aplikaciju razvila Informati~ka slu`ba poduze}a Hrvatske {ume d.o.o., a koristi se za planiranje proizvodnje.
Glavni su dijelovi sustava za pripremu proizvodnje: priprema doznake, plan sje~a, plan proizvodnje i plan prodaje.
Croat. j. for. eng. 33(2012)1
77
I. Stanki} et al.
Productivity Models for Operational Planning of Timber Forwarding in Croatia (61–78)
Unutar dijela za izradu plana proizvodnje nalazi se i modul za izra~un normativa izvo`enja drva forvarderima.
Ovdje razvijen i opisan sustav za planiranje normativa izvo`enja drva forvarderima uskoro zapo~inje s operativnom primjenom u hrvatskom dr`avnom {umarstvu.
Klju~ne rije~i: forvarder, norme proizvodnosti, planiranje, nizinske {ume, Hrvatska
Authors’ addresses – Adresa autorâ:
Igor Stanki}, PhD
e-mail: igor.stankic@sumfak.hr
Assoc. Prof. Tomislav Por{insky, PhD
e-mail: porsinsky@sumfak.hr
Department of forest engineering
Forestry Faculty, University of Zagreb
Sveto{imunska 25, HR-10000 Zagreb
CROATIA
Received (Primljeno): September 25, 2011
Accepted (Prihva}eno): May 22, 2012
78
@eljko Toma{i}, PhD
e-mail: zeljko.tomasic@hrsume.hr
Ivica Tonkovi}, dipl. ing.
e-mail: ivica.tonkovic@hrsume.hr
Marko Frnti}, dipl. ing.
e-mail: marko.frntic@hrsume.hr
Hrvatske {ume d.o.o. (Croatian forests LLC)
Directorate
Vukotinovi}eva 2, HR-10000 Zagreb
CROATIA
Croat. j. for. eng. 33(2012)1
Original scientific paper – Izvorni znanstveni rad
Energy Use of and Emissions from the
Operation Phase of a Medium Distance
Cableway System
Radomír Klva~, Radek Fischer, Alois Skoupý
Abstract – Nacrtak
This paper presents an assessment of the life cycle operation phase of forest cableways Larix
550 and Larix 3T with respect to energy requirements and environmental pollution caused
by emissions. Energy audit quantifies energy use based on the consumption of fuels and
lubricants. Energy balance includes both the energy content and the energy needed for the
production of fuels and lubricants. Fuel consumption measured for one year ranged from
1.2 – 1.4 l/m3. Based on the consumption of fuels and lubricants the paper quantifies the
amount of emissions in two scenarios (minimum consumption and maximum consumption) with a special focus on GHG emissions. Calculations are made of emissions for diesel
fuel and for the alternatively applicable rape-seed methyl ester (RME), and a calculation is
also made of emissions originating from fossil sources. By using RME as a fuel, the amount
of CO2 emissions from fossil sources discharged into the environment can be reduced by
3.4 kg per a cubic meter over the bark of timber extracted by cableway.
Keywords: GHG emissions, energy audit, fuel consumption, oil consumption
1. Introduction – Uvod
Anthropogenic greenhouse gases essentially affect the climate and a reduction of their emission into
environment is one of primary objectives of the current EU environmental policy. In order to achieve the
goal, it is absolutely necessary to increase the share
of energy from renewable sources, where in fact a
zero balance of CO2 originating from fossil resources
can be expected. However, clear zero balance of carbon dioxide is impossible in this case because of fossil
fuel consumption during production of renewable
energy sources.
Nowadays each product is loaded with a certain
share of primary fossil resources and hence with a
share of Green House Gas (GHG) emissions into
environment. The impact of any technology (system)
or product onto environment can be assessed by LCA
methodology, which can identify inputs and outputs
including their environmental impact (ISO 14040-2
standards, revised in 14044).
Also the main source of energy for logging and
hauling machines used in forest operations are fossil
fuels. Klvac et al. (2003) quantified the share of indiCroat. j. for. eng. 33(2012)1
vidual phases of the machine life cycle in the total
energy consumption of fully mechanized technology in the conditions of Ireland. Phases included in
the calculations were as follows: machine manufacture, repairs (including maintenance) and operation.
The phase of disposal or recycling, which also participates in the energy balance, was not included. Results of research showed that the share of machine
operation phase in the total energy balance amounts
to approximately 80%. Athanassiadis (2000) established the energy use and the amount of emissions
from a fully mechanized technology in Sweden at 82
MJ per cubic meter of wood processed, presenting
the values of emissions for three fuel types: EC3, EC1
and RME. However, in his work the emissions are
only quantified without establishing their share of
fossil resources.
Berg (1996 and 1997) compared emissions from
motor-manual and mechanized technologies in clear
felling and shelterwood felling on the basis of the
amount of combusted fuel. His works demonstrate
that mechanized technology loads environment with
emission substances rather more than motor-manual technology, and that shelterwood system puts
79
Radomír Klva~ et al.
Energy Use of and Emissions from the Operation Phase of a Medium Distance System (79–88)
on environment a greater load of CO2 and NOx emissions than clear-felling system due to a higher number of machine passes and their lower productivity.
Karjalainen and Asikainen (1996) and Sambo (1997)
estimated fuel consumption in the forestry of Finland and Canada. Based on the estimates, Karjalainen and Asikainen (1996) established the amount
of emissions into environment.
The expected CO2 emissions can be determined
on the basis of molecular formula, carbon-hydrogen
ratio (C:H), energy content and other factors (Calais
and Sims 2006). However, as they mentioned, the
simple calculation of CO2 emissions based on the
C:H ratio on stoichiometric basis is rather naive because the emissions and their composition are also
affected by other factors. Moreover, the energy content in fuels was published by many authors with
different results. Grägg (1994, 1998, 1999) and Furuholt (1995) established fuel energy content as follows: EC3 (Swedish Environmental Class 3 Fuel) =
36 MJ/l, EC1 (Swedish Environmental Class 1 Fuel)
= 35.3 MJ/l, and RME (Rapeseed Methyl Ester) =
33.1 MJ/l. Altin et al. (2001) determined the energy
Table 1 Emission factors of diesel engine (g/MJ of engine output) generated in combustion (Athanassiadis 2000)
Tablica 1. Faktori emisije dizelskih motora pri sagorijevanju, g/MJ
(Athanassiadis 2000)
CO2
CO
HC
NOX
PM
Diesel
260
1.26
0.114
2.342
0.197
RME
260
0.87
0.022
2.917
0.148
content of diesel fuel at 36.14 MJ/l, McDonell (1996)
mentions the value of 36.55 MJ/l for diesel and
35.67 MJ/l for a mixture with 25% of semi-refined
rapeseed oil and 75% of diesel.
Emissions generated in combustion can be related to the engine output power, where they depend
on thermal efficiency, i.e. on the capacity of transforming fuel energy to engine efficiency. Thermal
efficiency of engines depends on the rate of compression and on the octane or cetane number of the fuel.
Hamilton (2000) presented the relation between thermal efficiency, compression ratio and octane number
for carbureted spark-ignition engines.
Table 2 Emission factors of compression–ignition engines (C) and spark–ignition engines (S) in various machines as related to engine output power
(kg/kWh) (USEPA 1985)
Tablica 2. Faktori emisije dizelskih (C) i benzinskih (S) motora kod razli~itih strojeva s obzirom na snagu motora (kg/kWh) (USEPA 1985)
Wheeled tractor
Kota~ni traktor
Scraper
Skrejper
S
Wheeled
dozer
Kota~ni dozer
C
S
1.90E-01
4.70E-03
3.28E-03
3.28E-03
2.06E-03
3.78E-04
3.41E-04
2.15E-04
3.75E-04
3.75E-04
1.62E-04
1.05E-02
1.60E-02
8.54E-03
1.09E-02
1.00E-02
1.00E-02
9.57E-03
PM10
9.28E-04
1.70E-03
4.84E-04
5.51E-04
1.06E-03
1.06E-03
8.38E-04
SO2
1.14E-03
1.14E-03
3.04E-04
1.16E-03
1.21E-03
1.21E-03
1.17E-03
VOCs
1.01E-03
2.36E-03
7.16E-03
5.00E-04
7.40E-04
7.40E-04
4.80E-04
Off-highway
truck
Terenski
kamion
C
S
C
S
Pollutant
Zaga|iva~
Track-type
tractor
Vrsta stroja
C
CO
2.88E-03
9.84E-03
Formaldehyde
2.28E-04
NOX
C
S
Tracked
loader
Utovariva~
gusjeni~ar
CO
3.63E-03
2.19E-01
3.03E-03
4.70E-03
8.08E-03
2.71E-01
6.16E-03
2.66E-01
Formaldehyde
2.64E-04
2.98E-04
1.34E-04
2.95E-04
2.63E-04
3.43E-04
2.72E-04
2.98E-04
NOX
1.18E-02
7.27E-03
1.25E-02
1.09E-02
1.75E-02
7.08E-03
1.48E-02
6.48E-03
PM10
1.08E-03
4.21E-04
8.78E-04
6.73E-04
1.04E-03
5.27E-04
1.21E-03
4.06E-04
SO2
1.15E-03
3.19E-04
1.14E-03
1.19E-03
1.34E-03
3.73E-04
1.25E-03
3.54E-04
VOCs
1.59E-03
7.46E-03
1.49E-03
5.00E-04
1.30E-03
1.24E-02
1.35E-03
8.70E-03
Pollutant
Zaga|iva~
Wheeled loader
Kota~ni utovariva~
Grader
Grejder
Roller
Valjci
Miscellaneous
Razni strojevi
Conversion from kWh to MJ: 1 kWh = 3.6 MJ – Pretvorba iz kWh u MJ: 1 kWh = 3,6 MJ
PM10 – particular matters up to 10 microns and less – Sitne ~estice <10 mikrona
VOCs – volatile organic compounds – [tetni organski spojevi
80
Croat. j. for. eng. 33(2012)1
Energy Use of and Emissions from the Operation Phase of a Medium Distance System (79–88)
Radomír Klva~ et al.
Table 3 Total emissions generated in petroleum (P) and diesel (D) manufacture by individual countries (Davison and Lewis 1999)
Tablica 3. Ukupna emisija iz proizvodnje benzinskih i dizelskih goriva, po dr`avama (Davison i Lewis 1999)
Country
Dr`ava
Austria / Austrija
Belgium / Belgija
Denmark / Danska
Finland / Finska
France / Francuska
Germany / Njema~ka
Greece / Gr~ka
Ireland / Irska
Italy / Italija
Netherlands / Nizozemska
Portugal / Portugal
Spain / [panjolska
Sweden / [vedska
Switzerland / [vicarska
UK / Engleska
CO2
(kg/GJ)
P
9.4
9.2
9.0
9.3
9.3
9.2
9.5
8.9
9.3
9.2
9.3
9.3
9.2
9.0
9.3
D
6.8
6.8
7.2
7.0
6.7
6.9
7.2
7.2
7.0
6.8
6.9
6.9
7.0
7.2
6.8
CO
(g/GJ)
P
5.4
5.1
5.1
5.6
5.1
5.1
5.8
5.0
5.4
5.1
5.4
5.4
5.5
5.4
5.1
D
5.0
4.6
4.6
5.1
4.6
4.6
5.3
4.5
4.9
4.6
4.9
4.9
5.0
4.8
4.6
NOX
(g/GJ)
P
45.7
42.2
43.2
45.6
42.2
43.2
49.3
42.5
46.0
42.4
45.2
45.2
44.7
45.8
42.4
D
39.1
36.0
38.0
39.4
35.8
37.1
43.2
37.4
39.9
36.2
39.0
39.0
38.8
40.5
36.1
VOCS
(g/GJ)
P
213.0
211.5
203.5
208.7
212.3
208.3
208.9
203.5
208.8
209.8
210.2
210.0
208.0
203.5
211.4
D
87.9
87.6
86.1
87.4
87.8
87.3
87.2
86.2
87.3
87.6
87.4
87.5
87.0
86.1
87.8
SO2
(g/GJ)
P
62.7
65.6
93.3
77.7
62.7
78.1
79.5
93.1
77.9
72.2
72.2
73.3
78.4
95.1
66.9
D
45.1
48.4
77.7
57.5
44.9
57.8
62.7
77.5
59.0
51.8
55.2
54.5
61.8
79.4
47.6
CH4
(g/GJ)
P
17.4
17.4
17.2
17.3
17.3
17.3
17.3
17.0
17.2
17.4
17.3
17.3
17.1
16.9
17.4
D
15.7
15.7
15.6
15.6
15.7
15.7
15.7
15.5
15.6
15.7
15.7
15.7
15.5
15.3
15.8
PM
(g/GJ)
P
2.7
2.4
1.8
2.4
2.5
2.2
2.4
1.8
2.3
2.3
2.4
2.4
2.3
1.9
2.4
D
1.1
1.0
1.4
1.3
1.0
1.2
1.4
1.4
1.2
1.1
1.2
1.2
1.3
1.4
1.1
PM – particular matters – Sitne ~estice
VOCs – volatile organic compounds – [tetni organski spojevi
Emission factors of compression-ignition engines
in combustion for harvester technologies were studied by Grägg (1999). They were established on engine
Perkins 1006-T (133.5 kW) for EC3 fuel and on engine
Valmet 420 DS (135.8 kW for EC3 and EC1 fuels).
RME emission factors were established by Grägg
(1994) on engine Scania DSC 1127 (144 kW). Based
on the measurements, Athanassiadis (2000) determined emission factors of compression-ignition engines per engine output in MJ – these are presented
in Table 1. In this study engine thermal efficiency
was set up for both fuels at a level of 40%.
Emission factors need to be expressed at the best
for each machine separately or the machines should
be at least put together to form appropriate groups.
Emission factors of various machine groups are studied and regularly updated by the United States Environmental Protection Agency (USEPA 1985). Table
2 presents emission factors for various machine
groups with both spark- and compression-ignition
engines.
Emissions generated by combustion however do
not include all noxious substances emitted into the
environment from the use of fuels. A general comparison must take into account leakages of operation
fluids and the share of emissions generated in the
extraction, production, transport and distribution of
Croat. j. for. eng. 33(2012)1
fuels. Emissions developing during the production
of fuels were studied by Davison and Lewis (1999)
and Table 3 presents these emissions in some selected countries.
The study was focused on the most energy demanding part of the machine life cycle i.e. production
phase. The objective was to quantify the amount of
energy required for an extraction of functional unit
of production (m3) by cableways and to establish the
amount of emission load on environment.
2. Material and Methods – Materijal
i metode
Cableway types assessed within the study were
Model Larix 550 and Model Larix 3T. The powering
and transport unit was a farm tractor.
The cableway Model Larix 550 is designed as a
complete superstructure on the farm tractor (ZETOR
8540, 9540, 10540, or comparable types NEW HOLLAND, SAME, STEYR, JOHN DEERE), which provides a considerable advantage for passability through
the terrain and alleviates laboriousness of cableway
construction in the field. The cableway can be used
universally with a possibility of timber skidding
down the hill (100 – 550 m), up the hill and on the
81
Radomír Klva~ et al.
Energy Use of and Emissions from the Operation Phase of a Medium Distance System (79–88)
plain, with a fully suspended or semi-suspended
load. Based on the terrain character the assembly can
be made with a running line or with a skidding line.
Basic technical parameters: pulling force 35 kN, reach
550 m, carrying capacity 2 tons, time consumption
for track construction 48 hrs.
The cableway Model Larix 3T is a follow-up to
Model LARIX 550 from which the concept was adopted with the running line, capstan and suspension
onto the rear and front three-point linkage of a tractor. It differs in a reinforced load-bearing structure,
simplified design and operation, greater capacity of
drums and line boards. Carrying capacity of the
Model LARIX 3T is increased to 3 tons and reach up
to 850 m.
The system boundaries were set for the extraction
chain from stump to road side (felling, delimbing
and cross-cutting was not taken into the account) in
operation phase of cableway life cycle. The Functional Unit (FU) used in the analyses was cubic meter of
wood over bark (m3). In cases when the calculated
values were too small the unit 1000 m3 was used.
The model that was calculated in this study had
the following data inputs:
Þ Fuel, engine oil and transmission oil consumption, liters,
Þ Grease consumption, kg,
Þ Type of fuel: mineral or rape methyl esterm, RME,
Þ Type of oil in respect to biodegradability: mineral, synthetic or vegetable.
Note: Biodegradability is defined by CEC-L-33A-93, which is an international assignation of fuel
and grease production. A product is regarded as
biodegradable if it is degraded by at least 80% in 21
days (CEC 1995). Raw vegetable oils have a biodegradability of around 98% (if there are additives
included, it is 90–98%). Mineral oils have a biodegradability of about 20% and biodegradability of synthetic oils varies from 20 to 92% depending on the
type (Anon. 1994).
An energy audit should include the combustion
energy value of fuels and oils, and the energy used
during their production. Athanassiadis (2000) estimated a combined fuel and oil energy use for harvesting and forwarding of 82 MJ per m3ub (cubic
meter under bark), however the calculation failed to
include the energy used during the production of
oils. The energy consumed during the production of
diesel fuel is reported as ca. 4.5 MJ/l and 15.6 MJ/l
for biodiesel.
The energy value of mineral oil has also been
reported. Anon. (2000) presented lubricant mineral
oil as 38.5 MJ/l. Goering et al. (1982) designated the
energy value of vegetable oils (rapeseed oil used for
82
hydraulics and lubrication) as 39.6 MJ/kg (density
0.912 kg/l). In this study rapeseed oil was taken as
representative of vegetable oils. Synthetic oils are
usually produced from vegetable oil bases, with only
the »holder« (usually alcohol) of the fatty acid changed (Våg et al. 2000). Therefore, the same energy
value (39.6 MJ/kg by density 0.912 kg/l) may be assumed for synthetic oils. Våg et al. (2000) presented
energy consumption during the production of various lubrication oils as follows: mineral oil 45 MJ/l,
synthetic ester 22 MJ/l and rapeseed oil 12 MJ/l.
The energy audit of the cableway operation phase
in MJ/m3 of wood production was done as the sum of:
Þ Energy content of the fuel plus energy used in its
production.
The energy inputs were calculated as follows (listed respectively): mineral diesel fuel as 36.14 + 4.5 =
40.64 MJ/l and rape methyl ester as 33.1 + 15.6 =
48.70 MJ/l.
Þ Energy content of oils plus energy used during
their production.
In the current study, these energy inputs were
calculated as follows (listed respectively): vegetable
oil as 36.1 + 12 = 48.1 MJ/l, synthetic oil as 36.1 + 22 =
58.1 MJ/l and mineral oils as 38.5 + 45 = 83.5 MJ/l.
Exhaust emissions generated from the fuel were
calculated as a sum of emissions produced by fuel
combustion (Efc) and emissions produced during
the fuel production, transport and distribution (Efp).
With fuels that are products of photosynthesis in
which plants assimilate carbon dioxide from the atmosphere, the total balance is calculated without the
share of CO2 assimilated in this way. Anon. (2002)
informs in the section on greenhouse gas balances
that the fossil carbon content in RME amounts to
3.6% and the biomass carbon content is 69.7%.
The calculated exhaust emissions resulting from
fuel combustion (Efc) take into account the energy
content of fuel, emission factors related to the engine
output power, and the thermal efficiency of the fuel
combustion process. The calculation was made using the below formula:
Efc = Fc ´ Ef ´ Cv ´ Te
(1)
Where:
Efc Exhaust emissions from fuel
combustion, g/FU
Fc Fuel consumption, l/FU
Ef Emission factor, g/MJ of engine output
Cv Calorific value, MJ/l
Te Thermal efficiency
Emission factors used for the calculation were
those of wheel tractors (Table 2), only the calculation
of CO2 emissions was made with the emission factor
Croat. j. for. eng. 33(2012)1
Energy Use of and Emissions from the Operation Phase of a Medium Distance System (79–88)
at 263 g/MJ of engine output adopted from Athanassiadis (2000).
The calculation of emissions generated during
the fuel production, transport and distribution (Efp)
was based on the fuel energy content and emission
factors.
Efp = Fc ´ Ef ´ Cv
(2)
Where:
Efp Emissions generated in the phase
of extraction, production, transport and
distribution, g/FU
Fc Fuel consumption, l/FU
Ef Emission factor, g/MJ of engine output
Cv Calorific value, MJ/l
The emission factors used were those holding for
Austria (Table 3). Only the emission factor of 0.0862
used for HC was adopted from Athanassiadis (2000).
Emission load related to the consumption of oils
was calculated as a sum of emissions emanated in
the production of oils (Eop) and emissions generated
in the reprocessing of used oils for the purposes of
combustion (Eor). Emissions arisen in production
were calculated on the basis of emission factors
adopted from Ragnarsson (1994) and Marby (1999),
see Table 4. Emissions generated in the transport and
reprocessing of used oils for the purposes of combustion were calculated on the basis of emission
factors adopted from Lenner (1990) and from Stripple and Wennsten (1997), see Table 5.
Table 4 Total emissions from oil production phase, g/l (Ragnarsson
1994; Marby 1999)
Tablica 4. Ukupna emisija iz proizvodnje ulja, g/l (Ragnarsson 1994,
Marby 1999)
RBO
MBO
CO2
747.25
260.92
CO
1.1294
0.077
HC
0.9288
2.64
NOX
5.6169
2.662
PM
0.315
0.31
RBO – rapeseed based oils – Ulje uljane repice
MBO – mineral based oils – Mineralno ulje
Table 5 Total emissions from oil transport and reprocessing, g/l (Lenner
1990; Stripple and Wennsten 1997)
Tablica 5. Ukupna emisija iz transporta i prerade ulja, g/l (Lenner
1990, Stripple i Wennsten 1997)
Transport
Prijevoz
Reprocessing
Prerada
Total
Ukupno
CO2
CO
HC
NOX
PM
20.4
0.09
0.022
0.27
0.01
64.1
0.01
0.0001
0.13
0.01
84.5
0.1
0.0221
0.4
0.02
Croat. j. for. eng. 33(2012)1
Radomír Klva~ et al.
Emission load by oil production (Eop) was calculated on the basis of oil consumption data and on the
basis of emission factors as:
Eop = Oc ´ Ef
Where:
Eop Emissions emanated in the production
of oils, g/FU
Oc Oil consumption, l/FU
Ef Emission factor, g/l
(3)
Emission load from the transport and reprocessing of used oils for combustion was calculated on
the basis of emission factors and oil consumption.
Emission load from the transport for combustion
was calculated only in oils used for this purpose.
Eor = Oc ´ Ef
Where:
Eor Emissions emanated during transport
and reprocessing, g/FU
Oc Oil consumption, l/FU
Ef Emission factor, g/l
(4)
3. Results – Rezultati
Values calculated on the basis of one-year measurement were as follows:
Þ Productivity: 6 000 m3/year
Þ Fuel consumption: 1.2 – 1.4 l/m3
Þ Gear oil consumption: 6.7 l/1000 m3
Þ Engine oil consumption: 6.7 l/1000 m3
Þ Consumption of lubricants: 1.7 kg/1000 m3
Þ Greasing spray: 1 l/1000 m3
Total energy consumed during the operation phase in the form of fuels and lubricants, including the
energy required for their production, transport and
distribution was calculated for two scenarios. With
the use of minimum values (scenario 1) and maximum values (scenario 2) the energy consumption
was 50 MJ/m3 and 58 MJ/m3, respectively.
The highest share in total energy use was that of
the fuel – ca. 98%. The total energy use by consumed
fuel was calculated at 48.8 MJ/m3 for scenario 1 (fuel
consumption 1.2 l/m3) and 56.9 MJ/m3 for scenario
2 (fuel consumption 1.4 l/m3), respectively.
Energy use of 556.7 MJ/1000 m3 is associated with
gear oil consumption. Since the used engine oil was
of semi-synthetic character, there were two scenarios
of calculation, according to the ratio of mineral and
synthetic components in the oil. Energy consumption at a mineral-to-synthetic ratio of 80:20 and 35:65
was calculated to be 522.8 MJ/1000 m3 and 446.6
MJ/1000 m3, respectively. Energy use for lubricants
was calculated at 149.6 MJ/1000 m3. Energy con-
83
Radomír Klva~ et al.
Energy Use of and Emissions from the Operation Phase of a Medium Distance System (79–88)
Table 6 Emissions generated from fuel consumption, g/m3
Tablica 6. Emisija nastala potro{njom goriva, g/m3
Scenario 1 – Slu~aj 1.
Efc Diesel
Efp Diesel
Total Diesel
Efc RME
Efp RME
Total RME
Total RME*
CO2
4510.27
294.90
4805.17
4510.27
1187.63
5697.90
1420.59
CO
47.41
0.24
47.65
32.71
1.43
34.14
3.12
HC
1.82
3.74
5.56
0.36
1.27
1.63
1.29
NOX
77.09
1.70
78.79
94.82
8.18
103.00
103.00
Scenario 2 – Slu~aj 2.
PM
8.19
0.05
8.24
6.31
0.40
6.71
6.71
CO2
5261.98
344.05
5606.03
5261.98
1385.57
6647.55
1657.35
CO
55.31
0.28
55.59
38.16
1.67
39.83
3.65
HC
2.13
4.36
6.49
0.43
1.48
1.91
1.50
NOX
89.95
1.98
91.93
110.64
9.55
120.19
120.19
PM
9.56
0.06
9.62
7.36
0.46
7.82
7.82
Scenario 1: Fuel consumption 1.2 l/m3 – Slu~aj 1: Potro{nja goriva 1,2 l/m3
Scenario 2: Fuel consumption 1.4 l/m3 – Slu~aj 2: Potro{nja goriva 1,4 l/m3
Efc RME is calculated on the basis of emission increase or decrease between RME and EC3 adopted from Athanassiadis (2000)
Efc RME izra~unat na osnovi pove}anja ili smanjenja emisije izme|u RME i EC3 iz Athanassiadis (2000)
Efp RME calculated on the basis of emission factors adopted from Ragnarsson (1994) – Efp RME izra~unat na osnovi faktora emisije prema Ragnarsson (1994)
RME* calculated emissions which originate only from the fossil sources – RME* izra~unate emisija samo iz fosilnih goriva
Table 7 Emissions generated from the consumption of lubricants (g/1000 m3)
Tablica 7. Emisija nastala potro{njom maziva, g/1000 m3
Scenario 1 – Slu~aj 1.
Eop
Eor
Total
CO2
4885.88
1132.30
6018.18
CO
2.66
1.34
4.00
HC
40.55
0.30
40.84
Scenario 2 – Slu~aj 2.
NOX
47.16
5.36
52.52
PM
5.04
0.27
5.31
CO2
6352.17
1132.30
7484.47
CO
5.83
1.34
7.17
HC
35.39
0.30
35.69
NOX
56.07
5.36
61.43
PM
5.05
0.27
5.32
Scenario 1: Fully mineral gear oils, semi-synthetic engine oil (mineral-to-vegetable ratio 80:20) and fully mineral lubricants
Slu~aj 1.: Mineralna motorna ulja, polusinteti~ka motorna ulja (omjer mineralnih i biljnih ulja 80 : 20) i mineralna maziva
Scenario 2: Fully mineral gear oils, semi-synthetic engine oil (mineral-to-vegetable ratio 35 : 65) and fully mineral lubricants
Slu~aj 2.: Mineralna motorna ulja, polusinteti~ka motorna ulja (omjer mineralnih i biljnih ulja 35 : 65) i mineralna maziva
sumption from the greasing spray was calculated at
78.4 MJ/1000 m3.
The calculation of emission load on environment
was made separately for emissions emanated from
the use of fuels and for emissions arisen from the use
of oils. In both cases the calculation was made for two
scenarios. The scenarios in fuels were established
according to fuel consumption, i.e. scenario 1 with a
minimum consumption (1.2 l/m3) and scenario 2
with a maximum consumption (1.4 l/m3). RME can
be used as an alternative fuel and therefore a calculation was carried out of emissions emanated in using RME, too. As to the use of diesel oil, it can be
stated that all emissions originated from fossil sources. In the case of RME, however, a certain amount of
emissions originates from renewable sources and
therefore, emissions from fossil sources were calculated for the use of RME (in tables designated as
RME*). Scenarios for oils were set up according to
different types of oils used, i.e. scenario 1 is based on
using fully mineral gear oils, semi-synthetic engine
84
oil with ratio 80:20 and mineral lubricants, while
scenario 2 is based on using fully mineral gear oils,
semi-synthetic engine oil with the ratio 35:65 and
mineral lubricants.
The minimum total CO2 emission load on environment by cableway operation was determined
at 4.8 kg/m3 of wood extracted from stump to roadside in case of scenarios most favorable regarding
emissions. Detailed calculated emissions associated
with the consumption of fuels and the consumption
of oils and lubricants are presented in Table 6 and
Table 7, respectively.
4. Discussion and Conclusions
Rasprava i zaklju~ci
Energy and emissions generated from oil consumption are almost irrelevant compared to energy
and emissions related to fuel consumption.
Sheehan et al. (1998) enumerated the amount of
energy used and emissions in using fuels based on
Croat. j. for. eng. 33(2012)1
Energy Use of and Emissions from the Operation Phase of a Medium Distance System (79–88)
Radomír Klva~ et al.
Table 8 Inputs of primary energy for production, transport and distribution of diesel-based fuels and SME
Tablica 8. Ulo`ena energija za proizvodnju, prijevoz i distribuciju dizelskih i biolo{kih goriva
Stage – Faza proizvodnje
Domestic production of diesel, U.S.A. – Doma}a proizvodnja dizela, SAD
Production abroad – Inozemna proizvodnja dizela
Transport of diesel from domestic resources – Prijevoz dizela iz doma}ih izvora
Transport of diesel from foreign resources – Prijevoz dizela iz stranih izvora
Refining – Rafiniranje
Fuel transport – Prijevoz goriva
Total – Ukupno
Soy production – Proizvodnja soje
Soy transport – Prijevoz soje
Soy pressing – Prerada soje
Soy oil transport – Prijevoz sojina ulja
Soy conversion to SME – Proizvodnja sojina metil estera
SME transport – Prijevoz SME
Total – Ukupno
diesel and soy methyl ester (SME) in U.S.A. and
found out that in using classical extraction and refining techniques an investment of additional 1.2 MJ
of primary energies is required per each 1 MJ of
energy from diesel-based fuels and additional 0.311
MJ per each 1 MJ SME (see Table 8).
The emission load on environment from the fossil
sources is markedly lower with methyl esters (RME
and/or SME), the fact speaking for their preferred
use. The question, however, of their practical application as related to engine functionality and service
life, remains unanswered.
Energy use of fully mechanized technologies was
calculated by Athanassiadis et al. (2000) and Klvac et
al. (2003). The use of energy per FU is considerably
lower in cable transport, as a result of the lower
consumption of fuels and lubricants per FU. The
operation phase of the life cycle is the part with the
greatest share in total energy and emission requirements.
Generally, the issue of energy and emissions from
forest operation has been widely discussed in Karjalainen et al. (2001) study, made as part of COST Action E9. In detail, Schwaiger and Zimmer (2001) built
up their study on 0.9 kg/m3 cableway fuel consumption, which is lower compared to the results
obtained in this study. Also the emission factors are
slightly different. Moreover, it is difficult to identify
from which source the emission factors were adopted and whether the emission factors cover both combustion and production, respectively. However, usCroat. j. for. eng. 33(2012)1
Inputs of primary energies, MJ/MJ
Ulo`ena energija, MJ/MJ
0.5731
0.5400
0.0033
0.0131
0.0650
0.0063
1.2007
0.0656
0.0034
0.0796
0.0072
0.1508
0.0044
0.3110
% of inputs – % ulo`ene energije
47.73%
44.97%
0.28%
1.09%
5.41%
0.52%
100%
21.08%
1.09%
25.61%
2.31%
48.49%
1.41%
100.00%
ing the same average fuel consumption, the amount
of emission produced by cableway system would be
comparable.
The productivity of cableways is significantly affected by felling methods, possible pre-bundling and
by the number of choker setters as published by
Visser and Stampfer (1998). These authors presented
a markedly improved productivity of cableways
(30 – 40 %) as compared with the power saw if the
felling is made by harvester and if the logs are pre-bundled. As to the number of choker setters they
concluded that in sites prepared in this way it is
useful to have only one choker setter. The study was
made both in deciduous and in coniferous stands.
The employment of harvester technologies for logging operations in broadleaved stands is unsubstantiated in the conditions of the Czech Republic and
results in considerable problems. This is why a lower
energy consumption and emission load for using
harvester in logging can be expected according to
Visser and Stampfer (1998) only with the cableway
working in spruce stands.
Fuel consumption was measured in main felling
operations. Berg (1997) studied the environment
load with fossil fuels at different forest operations.
He found that as compared with the clear felling, the
share of emissions is higher by 10% and 20% in felling and skidding operations, respectively, in the
shelterwood system. The calculations suggest that
fuel consumption is by about 10% higher in the
shelterwood system.
85
Radomír Klva~ et al.
Energy Use of and Emissions from the Operation Phase of a Medium Distance System (79–88)
The amount of greenhouse gas emissions produced from alternative fuel (RME) is higher than
from diesel. However, if the calculation is made only
for carbon dioxide emitted from fossil sources, the
negative environmental load is significantly lower.
It has been calculated that the share of CO2 emissions from fully mechanized harvesting system in
the national context of countries with high forest
coverage such as Sweden was 1% (Athanassiadis
2000). By using methylesters in diesel engines of
mechanized logging technologies, the expected considerable reduction (by up to 70%) of CO2 emissions
originating from fossil sources will be accompanied
by a 30% increase of NOx emissions.
Acknowledgements – Zahvala
This paper was prepared within the framework
of research projects of the Ministry of Education of
the Czech Republic »Forest and Wood. Support to a
functionally integrated forest management.«, MSM
6215648902 and of the Ministry of Agriculture of the
Czech Republic »Sophisticated model for nature –
friendly timber haulage evaluation«, QH71159. The
authors also wish to express their thanks to contractors for enabling the collection of data.
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Sa`etak
Potro{nja energije i emisija {tetnih plinova pri radu `i~are
Kako stakleni~ki plinovi zna~ajno utje~u na klimatske promjene, smanjenje je njihove emisije jedan od
primarnih ciljeva okoli{ne politike Europske unije. Kako bi se ispunili zadani cilj, potrebno je ponajprije pove}ati
udio energije dobivene iz obnovljivih izvora, gdje nema emisije CO2 iz fosilnih goriva. U dana{nje vrijeme svaki je
proizvod optere}en s odre|enim udjelom primarnih fosilnih goriva te stoga i s odre|enom emisijom stakleni~kih
plinova. Utjecaj bilo koje tehnologije ili proizvoda na okoli{ mo`e se procijeniti pomo}u metode `ivotnoga ciklusa,
koja definira ulazne i izlazne parametre te njihov utjecaj na okoli{ (norma ISO 14040-2). U radu je opisana
energetski najzahtjevnija faza `ivotnoga ciklusa proizvoda, na primjer faza proizvodnje. Cilj je ovoga rada bio
odrediti koli~inu energije potrebne za izno{enje jedinice proizvoda (m3) pomo}u `i~are te odrediti koli~inu emisije i
utjecaj na okoli{.
Istra`ivane su `i~are Larix 550 i Larix 3T, koje su kao transportno i pogonsko sredstvo koristile poljoprivredni
traktor. @i~ara Larix 550 napravljena je kao nadogradnja poljoprivrednoga traktora (ZETOR 8540, 9540, 10540 ili
bilo kojega sli~noga (NEW HOLLAND, SAME, STEYER, JOHN DEERE), {to joj pru`a odre|ene prednosti pri
kretanju po terenu te olak{ava posao postavljanja `i~are za rad. @i~are se mogu koristiti prilikom svih na~ina rada,
pri privla~enju niz brdo (100 – 550 m), privla~enju uz brdo te privla~enju na ravnom. Ovisno o svojstvima terena,
`i~ara mo`e biti postavljena s beskona~nim nosivim u`etom ili s u`etom za privla~enje. Osnovne su tehni~ke
zna~ajke `i~are: vu~na sila 35 kN, doseg u`eta 550 m, nosivost 2 t, vrijeme postavljanja 4 – 8 sati. @i~ara Larix 3T
razvijena je na principu `i~are Larix 550 s beskona~nim nosivim u`etom, a mo`e se postaviti i na prednju i na
stra`nju trozglobnu poteznicu traktora. Model 3T razlikuje se od modela 550 u poja~anoj nosivoj strukturi,
pojednostavljenom dizajnu i upravljivosti, u ve}im bubnjevima, pove}anoj nosivosti (3 t) i pove}anom dosegu (850
m). Energetska bilanca sadr`i energetski sadr`aj i energiju potrebnu za proizvodnju goriva i maziva.
Potro{nja goriva koja je se mjerila kroz jednu godinu iznosila je 1,2 – 1,4 l/m3, potro{nja je ulja za opremu
iznosila 6,7 l/1000 m3, potro{nja je ulja u motoru iznosila 6,7 l/1000 m3, tokom istra`ivanja potro{eno je i 1,7
kg/1000 m3 te 1 l/1000 m3 spreja za podmazivanje. Godi{nja je proizvodnja iznosila 6000 m3. Potro{nja je energije
izra~unata za dva slu~aja, gdje su u prvom slu~aju kori{tene minimalne vrijednosti, a u drugom slu~aju
maksimalne vrijednosti. Potro{nja energije u istra`ivanom razdoblju iznosila je za prvi slu~aj 50 MJ/m3, a za drugi
slu~aj 58 MJ/m3. Na osnovi potro{nje goriva i maziva u radu je odre|ena koli~ina emisije s posebnim osvrtom na
Croat. j. for. eng. 33(2012)1
87
Radomír Klva~ et al.
Energy Use of and Emissions from the Operation Phase of a Medium Distance System (79–88)
emisiju stakleni~kih plinova (tablice 6 i 7). Tako|er je istra`ivana i potro{nja energije ovisno o omjeru smjese ulja
koje je kori{teno za stroj i opremu; tako su kori{tena polusinteti~ka ulja omjera smjese 80 : 20 i 35 : 65. Energetska je
potro{nja iznosila 556,7 MJ/1000 m3 za ulje 80 : 20, a za ulje 35 : 65 energetska je potro{nja iznosila 446,6 MJ/1000
m3. Energetska je potro{nja za maziva iznosila 149,6 MJ/1000 m3, a za sprej za podmazivanje 78,4 MJ/1000 m3. U
tablicama 6 i 7 izra~unate su emisije za dizelsko gorivo i poslije primijenjeno biogorivo uljane repice (RME).
Tako|er je izra~unata emisija koja potje~e od fosilnih goriva. Uporabom se biogoriva uljane repice koli~ina emisije
CO2 iz fosilnih goriva mo`e smanjiti za 3,4 kg/m3 privu~enoga drva.
Klju~ne rije~i: emisija stakleni~kih plinova, energetska bilanca, potro{nja goriva, potro{nja maziva
Authors’ addresses – Adresa autorâ:
Received (Primljeno): June 8, 2011
Accepted (Prihva}eno): February 07, 2012
88
Asocc. Prof. Radomír Klva~
e-mail: klvac@mendelu.cz
Mr. Radek Fischer
e-mail: xfische3@node.mendelu.cz
Assoc. Prof. Alois Skoupý,
e-mail: skoupy@mendelu.cz
Mendel University in Brno
Faculty of Forestry and Wood Technology
Department of Forest and Forest Products Technology
Zemedelska 3
613 00 Brno
CZECH REPUBLIC
Croat. j. for. eng. 33(2012)1
Original scientific paper – Izvorni znanstveni rad
Potential Mechanisms for Co-operation
between Transportation Entrepreneurs and
Customers: A Case Study of Regional
Entrepreneurship in Finland
Palander Teijo, Vainikka Mika, Yletyinen Antti
Abstract – Nacrtak
The objectives of this study were to investigate how to increase co-operation in the regional
entrepreneurship approach of wood transportation and facilitate the ongoing outsourcing of
wood-procurement responsibilities in the Finnish forest industry. We examined co-operation between transportation entrepreneurs (suppliers) and between suppliers and the forest
industry (customers). A questionnaire was sent to wood transportation entrepreneurs working in the wood-procurement network of the customers. The entrepreneurs felt that the most
interesting form of consortium between suppliers, which would let them respond better to
outsourcing, would be the formation of a joint venture responsible for sales and marketing of
their services. Such a company would develop an overall contract with each customer, and
then each shareholder in the joint venture would sign their own contracts with the venture
to share the work. All transactions would be based on invoicing instead of the current salary-based approach. However, entrepreneurs did not believe that their profitability would increase by expanding their responsibilities in the current entrepreneurial environment. If the
aim of co-operation is to outsource the wood transportation function, decision-makers in the
Finnish forest industry should modify the current environment so that larger, more organized consortia of wood suppliers would become more profitable than they presently are in the
regional entrepreneurship approach.
Keywords: Wood procurement, Outsourcing, Regional entrepreneurship, Networking
1. Introduction – Uvod
Almost all of the wood used by the Finnish forest
industry is transported by trucks at some stage of the
wood-procurement network, from the forest to the
mill. Currently, approximately 850 Finnish wood
transportation companies own about 1700 trucks and
employ about 2600 drivers. Three-quarters of these
wood transportation companies are small; families
own one or two trucks, which usually deliver more
than 90% of wood to a single customer. Nowadays,
three of the largest customers (»Stora Enso«, »UPM«,
and »Metsäliitto«) dominate the wood-procurement
field, with a combined market share of about 90% of
wood that is transported in Finland.
Traditionally, wood-procurement organizations
sign direct transportation contracts with each transCroat. j. for. eng. 33(2012)1
portation company. These contracts have been used
to strictly define the transportation operations that
the entrepreneurs are responsible for. Traditionally,
most of these contracts have been with employees of
the wood-procurement organizations, and specified
a fixed salary for the trucker. More recently, the forest industry has begun trying to outsource many of
its operations, including wood transportation, in an
effort to reduce its operating costs. However, this
transition is only partially complete, and the current
form of transportation entrepreneurship still retains
many features of the traditional system. As a result,
the kind of invoice-based (rather than salary-based)
entrepreneurship that is typical of outsourced work
markets has not yet become possible. In any outsourced business environment, entrepreneurs would
invoice their customers for the work that they actual-
89
T. Palander et al. Potential Mechanisms for Co-operation between Transportation Entrepreneurs and Customers ... (89–103)
ly do, rather than receiving fixed payments as part of
an employment contract (Beimborn et al. 2005). However, the current form of co-operation in transportation prevents this kind of invoicing. In the current
operating environment, cost-efficiency is based on a
large amount of the salary-based work performed
by many small-scale entrepreneurs and members of
their families. This environment provides relatively
low direct transportation costs. However, it prevents
the economies of scale that would become possible
with large-scale entrepreneurship.
The costs of a Finnish transportation company
have increased by 20% from year 2005 to 2010 (Fig.
1), and are shown in the financial statements as four
main cost sources: purchases (for example parts, maintenance, fuel) wages (for example wages, pension
contributions, indirect employee costs), other fixed
costs (for example upkeep, rent, insurances), and
capital costs (for example interest, depreciation). If
the management costs are considered as an indicator
of outsourcing, it seems that nothing has happened
since 2005 that could be interpreted as an increase of
outsourcing.
In the present study, wood suppliers were considered to be the transportation entrepreneurs, and
their customers to be the wood-procurement organizations in the forest industry. Customers incur transaction costs caused by the need to exactly specify the
transportation functions. The concept of transaction
cost to be used is strictly linked to the idea of the cost
of social division of labor (Coase 1998; Demsetz 2003;
Bertolini and Giovannetti 2006). In this study, these
transaction costs are described for the wood-procurement organizations that manage and control the
transportation function in the wood-procurement network (Fig. 2). According to Williamson (1981), the
determinants of transaction costs are frequency, specificity, uncertainty, limited rationality, and opportunistic behavior. Through transaction cost minimization and knowledge exchange, networking can lead
to higher performance of organization as a tool of
regional and industrial policy (Andreosso-O’Callaghan and Lenihan 2008). Globalization of the forest
industry has required steadily increasing efficiency
and decreasing staff size in the industry’s wood-procurement network in recent decades. If the wood
procurement organizations keep growing leaner, it
may become impossible to apply the traditional contracting model because the number of managers of
the forest industry is too small to perform the work
needed to manage and control the transportation
function.
In this changing entrepreneurial environment, the
forest industry is attempting to improve its cost-effectiveness by offering transportation contractors
extended entrepreneurship agreements that increase
their responsibilities (Högnäs 2000; Palander et al.
2006). Actually, extended entrepreneurship is the
first stage of ongoing process from contracting model of wood procurement network to outsourcing
model of wood supply network. Fig. 2 shows that,
after determining internal transaction costs separately in institutions and wood procurement companies, a decision can be made »whether to outsource
Fig. 1 Change of timber haulage truck’s cost index from 2005 (left) to 2010 (right) according to K. Palojärvi (personal communication June 15, 2010)
Slika 1. Promjena indeksa tro{kova kamiona za prijevoz drva od 2005. (lijevo) do 2010. (desno) prema K. Palojärvi (osobna komunikacija, 15. lipnja 2010)
90
Croat. j. for. eng. 33(2012)1
Potential Mechanisms for Co-operation between Transportation Entrepreneurs and Customers ... (89–103) T. Palander et al.
Fig. 2 Transaction model that shows institutions and market as a potential form of outsourcing to organize economic transactions. E.g., when the external
transaction costs of the wood procurement company A (ETC) are higher than the internal transaction costs (ITC), the company can grow (left side). If the
internal transaction costs of the wood procurement company A are higher than the external transaction costs the company can be downsized by
outsourcing (right side)
Slika 2. Model koji prikazuje institucije i tr`i{te kao potencijalni oblik izdvajanja u organizirane ekonomske transakcije. Kada su vanjski tro{kovi
transakcije (ETC) poduze}a za dobavljanje drva A ve}i od internih tro{kova transakcije (ITC), poduze}e mo`e rasti (lijeva strana). Ako su interni tro{kovi
transakcije poduze}a A ve}i od eksternih tro{kova, transakcija se poduze}a mo`e smanjiti izdvajanjem dijela poslova (desna strana)
or not to outsource wood transportation function«
based on external transaction costs of the wood procurement company. For the Finnish forest industry
the extended entrepreneurship is a logical consequence of the outsourcing of business functions that
is becoming increasingly common in international
markets. Based on a theory of transaction costs, outsourcing could potentially reduce the total costs of
procuring raw materials at the mill (Williamson 1975,
1985). If the theory is correct, the forest industry’s
overall cost-effectiveness and international competitiveness would improve.
Regional entrepreneurship is one form of extended entrepreneurship that emphasizes co-operation
between the wood supplier and the customer (Palander et al. 2006). In wood transportation sector
regional entrepreneurship is a new thing, even though
earth-moving and road-construction entrepreneurs
have used this approach for decades. In a typical
regional entrepreneurship application, the wood-procurement organization would sign transportation contracts with fewer entrepreneurs, each responsible for
a larger area (a »region«). These extended contracts
would include transportation tasks that are larger
and more diverse, and that include more responsiCroat. j. for. eng. 33(2012)1
bilities, than in conventional contracts. A regional
entrepreneur can fulfill their contract commitments
either by working alone or by co-operating with
other entrepreneurs. The latter form of co-operation
can occur via different forms of consortium:
Þ Subcontracting, in which one entrepreneur buys
services from other entrepreneurs, acting as sub-contractors,
Þ Joint venture, in which a group of companies (the
consortium) jointly signs a contract with a customer, and then consortium members share the
payments for the work on a pre-determined basis,
Þ Joint venture for sales and marketing, in which
the joint venture signs contracts with customers,
and shareholders sign contracts with the joint
venture (with all monetary transactions based on
invoicing rather than salaries),
Þ Merger, in which the separate companies form a
single new company, with the original equipment either transferred or sold to that company;
the entrepreneurs then become shareholders in
the new company and close the old companies.
Shareholders work for this company and select a
manager for the merged company,
91
T. Palander et al. Potential Mechanisms for Co-operation between Transportation Entrepreneurs and Customers ... (89–103)
Þ Acquisition of another company, in which the
seller transfers their equipment to the buyer, and
subsequently works for the buyer.
Regional entrepreneurship has been adopted slowly by customers. Although »Stora Enso« is now beginning to investigate extended entrepreneurship contracts, several entrepreneurs working for »UPM-Kymmene« and »Metsäliitto« Cooperative have already
signed such contracts. To advance this development,
transaction costs can be used as a decision support.
However, transaction costs are difficult to calculate,
which may cause errors and uncontrolled variation
in the data. Recently, Bertolini and Giovannetti (2006)
have examined the important role played by the
co-operative movement and co-operative firms, which
allowed the reduction of transaction costs. Moreover, the networking literature takes a view that
co-operation is an essential component of new-firm
generation and growth (Jack et al. 2008). Before calculation transaction costs, a survey could be used as
a study method to learn the opinions of stakeholders
about the co-operation required by the operational
environment of consortium, regional entrepreneurship, extended entrepreneurship and outsourcing.
Studies suggest that outsourcing can be promoted by increasing the size of contracts, extending the
number of tasks and responsibilities included in the
contract, and giving entrepreneurs more freedom of
action, as proposed by Högnäs (2000). In wood transportation these actions require co-operation among
entrepreneurs to form consortia, which are potentially more profitable. Palander and Väätäinen (2005)
and Palander et al. (2006) noted that, based on current trend, there will be fewer, larger transportation
consortia in the future, with increased networking
among them. Networks can be vital living organisms,
changing, growing and developing over time. Therefore, networks will create the entrepreneurial environment as suggested by Jack et al. (2008). The present transportation functions are also becoming differentiated and focused in different ways so that the
wood-procurement network will have new actors,
including workers who act as coordinators between
the current organizations. Furthermore, Bengtsson
and Kock (2000) have noted that competition and
co-operation can exist simultaneously within a network of organizations.
In the study conducted by Ala-Fossi et al. (2004),
service suppliers regarded joint ventures more positively than subcontracting as a co-operation model
for the outsourced activities. On the other hand,
Palanderet al. (2006) found that both service suppliers and customers regarded joint ventures among
transportation service suppliers as the weakest organizational alternative. These contradictory results
92
may have resulted from the fact that many of the
entrepreneurs failed to understand the nature or
implications of outsourcing. In the previous studies,
comparisons of alternatives were therefore based
more on images than on the actual knowledge. This
lack of knowledge may have occurred because, at
that time, the industry was just beginning to gain
experience with regional entrepreneurship and had
not yet clearly defined its needs.
Entrepreneurs who have signed contracts with
extended responsibilities have repeatedly identified
deficiencies in current models of regional entrepreneurship. The inability to work through invoicing,
because customers have not yet replaced their traditional payment model and disadvantages of the current transportation routing methods were seen as
significant obstacles to the development of regional
entrepreneurship. The former problem prevents the
development of genuine business expertise, since if
outsourcing were based on invoicing, theories would
provide instruments and methods of coordination
that could be applied to improve business practices
(Beimborn et al. 2005; Bititci et al. 2005). Currently, it is
impossible to apply these tools in Finland because
wood-procurement organizations still pay entrepreneurs a piece rate according to the quantity of wood
delivered. In a theory of outsourcing, regional entrepreneurship would permit invoicing rather than salary-based work.
The second barrier to efficient regional entrepreneurship relates to the problem of routing. Currently,
wood-procurement organizations tell each truck
where to go to pick up wood. This leaves entrepreneurs little freedom to organize their own resources
(time, trucks, drivers, routes), and often leads to operational inefficiencies if (for example) this prevents an
entrepreneur from taking advantage of other opportunities, such as the chance to carry payload during a
backhaul instead of traveling empty. For entrepreneurs, it would be beneficial to be allowed to control
the volume they transport and the routing of their
vehicles. This would provide many benefits both for
them and for the wood-procurement organizations
they serve. Benefits mentioned by entrepreneurs include group transport (i.e., the ability to group several
trucks to haul a roadside inventory too large for a
single entrepreneur to handle), a high vehicle utilization rate, backhauling, improved inventory control,
improved control of seasonal variation in the wood
supply, various synergies, and a better understanding
of wood harvesting and the overall wood-procurement logistics chain (Palander and Väätäinen 2005).
To permit the evolution of regional entrepreneurship and make it part of the wood-procurement network, more studies are needed to describe opportuniCroat. j. for. eng. 33(2012)1
Potential Mechanisms for Co-operation between Transportation Entrepreneurs and Customers ... (89–103) T. Palander et al.
ties for co-operation and the operational environment.
Steps should also be taken to prepare for the increased co-operation of transportation entrepreneurs. Understanding the opinions (concerns and priorities) of
entrepreneurs would facilitate the development of
regional entrepreneurship; at a minimum, it would
promote the development of current consortia of entrepreneurs by providing insights into future changes
in their operating environment. For example, there
may be an optimal company size in terms of profitability, as suggested by Soirinsuo and Mäkinen (2009).
The results of another study suggested that transportation entrepreneurs with large company sizes were
more interested in regional entrepreneurship than
small entrepreneurs (Ala-Fossi et al. 2004). However,
the study did not determine why the entrepreneurs of
large sized companies regarded regional entrepreneurship more positively than was the case with the
other transportation entrepreneurs. We speculate that
this attitude may result from the greater resources
available to the large companies, and their working
experience in larger regions, which make the responsibility of operating on a regional scale seem less
intimidating. Further, the fear of incorrect decisions
leading to ineffective investments can slow the development of regional entrepreneurship during the
amortization period for these investments.
Our review of the research results and theories
related to outsourcing and regional entrepreneurship suggests that both should be based on co-operation, but co-operation between actors requires improvement. It has been assumed that regional entrepreneurship will remain uncommon because it is not
clear how to encourage co-operation between wood
suppliers and between suppliers and their customers in the current changing operating environment.
Therefore, the objectives of the present study were to
investigate how to increase co-operation in the wood
transportation operations and facilitate the ongoing
outsourcing of wood-procurement responsibilities
in the Finnish forest industry. To support this research, we surveyed entrepreneurs to learn their opinions about the following categories of questions: (1)
What factors prevent regional entrepreneurship from
becoming more common? (2) How do customers
perceive regional entrepreneurship? (3) How prepared are entrepreneurs to develop co-operative agreements, and what possibilities do they see arising
from these agreements? (4) Are entrepreneurs willing to form various kinds of consortia, and what are
the perceived implications for their profitability? We
also focused on the questions of supplier-customer
relationships and transportation company size, since
these are possible explanatory factors for the different opinions of respondents.
Croat. j. for. eng. 33(2012)1
2. Research Data and Study Methods
Podaci i metode istra`ivanja
The data used in this study was obtained from
Finland in 2006 using a questionnaire that was carefully tested and revised before using it to collect the
research data. The survey was distributed by mail to
wood transportation entrepreneurs belonging to the
Finnish Transport and Logistics Association (SKAL).
This association represents transportation entrepreneurs in negotiations with customers in work markets. About 410 wood transportation companies are
members of the association in the study area.
The target group for our survey comprised entrepreneurs who had not signed regional entrepreneurship contracts (n = 198). This group of entrepreneurs
had no prior knowledge of co-operation between
suppliers or between suppliers and their customers
within the wood-procurement network. In total, 84
entrepreneurs returned the questionnaire, and after
eliminating incorrect responses, we retained answers
from 76 entrepreneurs. Consequently, the final response rate was 39%. We included four regional entrepreneurs in the results because they had just begun working under the new form of environment.
Tests for non-response bias were made. According to
Director of the Timber Carriers Association, our survey provided a representative sample of Finnish wood
transportation entrepreneurs. On the other hand,
there were a few entrepreneurs who were not members of SKAL, but their percentage of the total wood
transported was sufficiently low to be irrelevant for
the survey. In addition, three of these entrepreneurs
worked mainly in Russia, so their data were not relevant because the target group in our study was wood
transportation entrepreneurs working in Finland.
We divided our questionnaire into three parts.
The first part asked entrepreneurs about their current situation and obtained other background information, such as the form of the company, the form of
their contract, the size of their company, and their
most important customer. We used the last two parameters as the basis for grouping the transportation
entrepreneurs. All respondents answered the same
questions so that we could compare the answers
between groups. We used the number of trucks as an
indicator of the size of a respondent’s operations; we
divided the entrepreneurs into three groups based
on the size of their company. Out of the 76 respondents, 44 had only one truck (»small company«).
Medium company (16 respondents) had two trucks,
and large company (16 respondents) had three or
more trucks. The biggest company had 12 trucks.
The transportation entrepreneurs supplied wood to
a total of eight customers, from which 6 had two
93
T. Palander et al. Potential Mechanisms for Co-operation between Transportation Entrepreneurs and Customers ... (89–103)
main customers and 70 entrepreneurs identified their
most important customer. We divided transportation entrepreneurs into five groups based on their
most important customer: »Stora Enso« was the most
important customer for 25 entrepreneurs, »UPM«
for 16 entrepreneurs, »Metsäliitto« for 10 entrepreneurs, and the Finnish »Forest and Park Service« for
9 entrepreneurs. The remaining 10 transportation entrepreneurs formed a group that worked for Other
Customers.
We found no statistically significant differences
in the number of years of experience between entrepreneurs with different company sizes. However,
owners of the large companies had, on average, been
working as transportation entrepreneurs for a little
longer (30 years) than entrepreneurs who owned
medium (23 years) or small (23 years) companies.
The number of working hours per week can vary
greatly for entrepreneurs depending on the season,
annual holidays, sick leave and time required to
repair their equipment. Our survey was distributed
in mid-winter and late winter, but the duration of the
work week was similar in both cases (an average of
68 hours per week). We found no statistically significant differences in working time between transportation entrepreneurs of different company sizes
or with different customers.
In the second part of the questionnaire, we asked
entrepreneurs about their attitudes towards the concept of regional entrepreneurship. To do so, we asked
entrepreneurs to state their opinions about various
statements using a seven-point Likert-like scale, ranging from »I fully agree« to »I fully disagree«. The
third part of the questionnaire investigated the co-operation between transportation entrepreneurs by
asking them to evaluate a series of statements concerning different forms of consortium, and particularly about whether they perceived these forms of
consortia as interesting and likely to be feasible. This
part of the survey employed »strategic gap analysis«
(Ansoff 1965), and contained statements that were
designed to evaluate the preparedness of entrepreneurs to choose different forms of consortium, and
opportunities to do so. We also asked the entrepreneurs to estimate the truthfulness of each statement. For many of the questions, we also gave entrepreneurs an opportunity to explain their responses,
and some of these responses provide possible explanations for the results.
We analyzed the data using SPSS-X (SPSS Inc
(1988) SPSS-X User’s Guide. 3rd ed. SPSS Inc., Chicago) in three stages. In the first stage, we summarized
the background information using averages for the
volume of activity and percentage shares of the response rates. The attitude results, based on the seven-
94
-point Likert-like scale, were analyzed based on the
relative shares of answers and based on a weighted
average of the responses. In the second stage, we
analyzed the answers using Kendall’s rank-correlation coefficient (t). In the third stage, we studied
groups of transportation entrepreneurs using nonparametric analysis of variance (the Kruskal-Wallis
test) and compared these groups two at a time using
the Mann-Whitney U-test. We used these tests (both
based on ordinals) because the variable values (answers) did not show a normal distribution, and the
tests let us test whether two independent samples
(groups) came from the same population. The former test revealed whether the groups being tested
were significantly different, after which we identified specific significant differences using the Mann-Whitney U-test in paired comparisons. Unless otherwise noted, we used the Mann-Whitney U-test and a
significance level of p < 0.05 for all results.
3. Results – Rezultati
The entrepreneurs thought that their most important customers had different opinions of regional
entrepreneurship (Kruskal-Wallis). According to the
entrepreneurs, »Stora Enso« was most negative about
regional entrepreneurship, with a significantly smaller Likert value (3.6) than the average (5.9) for those
who reported »Metsäliitto« as their most important
customer, which had the most positive attitude towards regional entrepreneurship. The mean Likert
value for entrepreneurs who provided wood for
»Stora Enso« was also significantly smaller than the
average (5.4) for the group that worked for »UPM«
and the average (5.0) for the group that worked for
the Finnish »Forest and Park Service«. The Likert
value for the group that worked for Other Customers (4.2) was significantly smaller than the values
for who that worked for »Metsäliitto« and »UPM«.
The entrepreneurs believed that their most important customer should inform them better about
the customer’s plans regarding regional entrepreneurship. The mean Likert value (2.6) for this statement was the lowest for entrepreneurs working for
»Stora Enso« and for entrepreneurs in medium companies (2.9), and the highest for entrepreneurs working for »Metsäliitto« (3.8) and for entrepreneurs in
small companies (3.4); however the differences were
not statistically significant. There was a statistically
significant correlation between the positive attitude
of the customer towards regional entrepreneurship
and the entrepreneur’s desire for more information
(t = 0.324).
Table 1 summarizes the responses of the entrepreneurs to our survey statements about regional
Croat. j. for. eng. 33(2012)1
Potential Mechanisms for Co-operation between Transportation Entrepreneurs and Customers ... (89–103) T. Palander et al.
Table 1 Levels of agreement with the statements regarding regional entrepreneurship. 1 = Fully disagree; 2 = Disagree; 3 = Mildly disagree; 4 = Don’t
know; 5 = Mildly agree; 6 = Agree; 7 = Fully agree. Entrepreneurs were divided into groups based on their company size (Small (1 truck) = S; Medium (2 trucks) =
M; Large (3 or more trucks) = L) and their most important customer (»Stora Enso« = A; »UPM« = B; »Metsäliitto« = C; »Forest and Park Service« = D; Other
Customers = E)
Tablica 1. Razina slaganja s tvrdnjama u vezi s regionalnim poduzetni{tvom. 1 = Uop}e se ne sla`em; 2 = Ne sla`em se; 3 = Blago se ne sla`em; 4 = Ne
znam; 5 = Blago se sla`em; 6 = Sla`em se; 7 = Potpuno se sla`em. Poduzetnici su podijeljeni u grupe prema veli~ini tvrtke (Mali /1 kamion/ = S; Srednji
/2 kamiona/ = M; Veliki /3 ili vi{e kamiona/ = L) i najva`nijim korisnicima (»Stora Enso« = A; »UPM« = B; »Metsäliitto« = C; »[umska i parkovna slu`ba«
= D; Ostali korisnici = E)
I understand what regional entrepreneurship means – Razumijem {to zna~i regionalno poduzetni{tvo
Regional entrepreneurship is a favorable development for the wood transportation
Regionalno je poduzetni{tvo povoljan razvoj za transport drva
The forest industry is only promoting regional entrepreneurship to transfer their wood-procurement
costs on to transportation entrepreneurs – [umska industrija promovira regionalno poduzetni{tvo
samo radi prebacivanja svojih tro{kova dobave drva na privatne prijevoznike
The bargaining position of a regional entrepreneur is significantly stronger than that of entrepreneurs
with a normal salary-based contract – Pregovara~ka pozicija regionalnih poduzetnika znatno je
ja~a od poduzetnika s normalnim platnim ugovorom
Regional entrepreneurship will lead to overcapacity in the wood transportation
Regionalno }e poduzetni{tvo rezultirati prekapacitiranjem u prijevozu drva
I have enough ability to negotiate on behalf of a consortium or a joint venture
Imam dovoljno sposobnosti da pregovaram u ime konzorcija ili za zajedni~ki pothvat/ulaganje
I am willing to expand the area in which I operate and to take on new responsibilities to become a
regional entrepreneurship
Voljan sam pro{iriti podru~je rada i preuzeti nove odgovornosti da postanem regionalni poduzetnik
A regional entrepreneurship would improve the cost-efficiency and profitability of the whole
wood-procurement network – Reginalno }e poduzetni{tvo pobolj{ati tro{kovnu u~inkovitost i
profitabilnost ukupne mre`e dobavljanja drva
I have enough knowledge of long-distance transportation routing and the planning of backhauls
Imam dovoljno znanja o odre|ivanju ruta i planiranju udaljenoga transporta
I have enough ability to make additional use of information technology
Imam dovoljno sposobnosti za dodatno kori{tenje informacijskih tehnologija
I have enough ability to found a joint venture that would take care of both harvesting and
transportation of wood – Imam dovoljno sposobnosti za zajedni~ki pothvat/ulaganje koji bi
pokrivao pridobivanje i transport drva istodobno
I have enough resources to purchase planning and data systems
Imam dovoljno sredstva za kupnju sustava za planiranje i podatke
I want more training in the fields of information and communications technology
@elim vi{e osposobljavanje u podru~ju informacijskih i komunikacijskih tehnologija
Regional entrepreneurship will become more common in the future
Regionalno }e poduzetni{tvo u budu}nosti postati uobi~ajenije
entrepreneurship, grouped by major customer and
company size. The entrepreneurs commonly believed that the forest industry was only promoting regional entrepreneurship to pass their wood-procurement costs to the transportation entrepreneurs (mean
Likert value = 6.2). The entrepreneurs who worked
for »Metsäliitto« and »Stora Enso« were least likely
to believe this statement (Likert values of 5.9 and 6.0,
Croat. j. for. eng. 33(2012)1
A
6.0
Customer
Korisnik
B
C
D
5.4 5.8 5.0
E
5.7
Company size
Veli~ina tvrtke
S
M
L
5.6 5.9 5.6
3.8
3.8
4.0
3.9
2.7
3.5
3.9
3.7
6.0
6.3
5.9
6.2
6.9
6.1
6.6
5.9
4.8
4.0
4.5
4.1
3.4
3.9
4.6
4.8
4.0
4.2
3.6
4.0
4.6
4.0
4.1
3.9
3.8
4.2
4.5
4.2
3.4
4.2
3.9
3.6
2.7
3.8
3.6
3.4
2.4
3.0
2.8
3.9
3.7
3.8
4.1
4.3
3.7
3.8
4.1
4.1
4.5
4.3
5.0
3.9
4.1
4.3
4.2
4.9
4.4
4.0
4.4
3.7
4.5
4.5
3.6
4.6
2.5
3.1
3.3
2.6
3.3
2.7
2.9
3.8
3.6
3.2
3.6
3.3
3.8
3.4
3.5
4.4
4.8
4.9
4.4
4.1
4.0
4.5
4.5
4.6
4.7
4.9
4.5
4.1
4.4
4.5
4.4
5.0
respectively). The entrepreneurs working for Other
Customers were most likely to believe this statement
(6.9). The differences were statistically significant
between »Metsäliitto« and Other Customers and between »Stora Enso« and Other Customers. The entrepreneurs who reported »Stora Enso« as their most
important customer were most likely (6.0) to believe
that they understood what regional entrepreneur-
95
T. Palander et al. Potential Mechanisms for Co-operation between Transportation Entrepreneurs and Customers ... (89–103)
Table 2 Entrepreneurs’ interest in and perceived feasibility of various forms of co-operation. 1 = Fully disagree; 2 = Disagree; 3 = Mildly disagree; 4 = Don’t
know; 5 = Mildly agree; 6 = Agree; 7 = Fully agree
Tablica 2. Interesi poduzetnika i percipirana izvedivost razli~itih oblika suradnje. 1 = Uop}e se ne sla`em; 2 = Ne sla`em se; 3 = Blago se ne sla`em; 4 = Ne
znam; 5 = Blago se sla`em; 6 = Sla`em se; 7 = Potpuno se sla`em
Form of co-operation – Oblik suradnje
Sub-contracting – Podugovaranje
Joint venture – Zajedni~ki pothvat/ulaganje
Joint venture for sales and marketing – Zajedni~ki pothvat/ulaganje za prodaju i marketing
Merger – Spajanje
Company acquisition – Kupnja poduze}a
ship means, whereas the entrepreneurs who worked
for the Finnish »Forest and Park Service« were least
likely (5.0) to share that belief. The difference between the two groups was statistically significant.
Most entrepreneurs were not interested in expanding their company into a regional entrepreneurship
(mean Likert score of 3.1). The entrepreneurs working for »UPM« were most interested (3.8) in expanding their company, whereas the entrepreneurs working for Other Customers were least interested (2.4).
This difference was statistically significant. The entrepreneurs who had large companies were slightly
more interested in expanding their company (3.9)
than the entrepreneurs of small (3.0) and medium
(2.8) companies, but the differences were not significant. The entrepreneurs who owned four or five
trucks believed more often than any other group
(small, medium, large) that the growth of their company would increase profitability (3.6), but at the
same time, they were more reluctant (3.3) than entrepreneurs of other large companies to expand their
company size. The entrepreneurs with four or five
trucks regarded regional entrepreneurship more positively (5.1) than any other group.
The entrepreneurs responded negatively (a mean
Likert value of 3.0) to the statement that they had
enough ability to found a joint venture capable of
taking care of both harvesting and transporting
wood. The entrepreneurs who owned four or five
trucks were the group that was most interested in
co-operation with harvesting entrepreneurs (4.2).
The entrepreneurs with large companies were more
positive (3.8) about this statement than the entrepreneurs with small companies (2.7), and the difference
was statistically significant. This was also true for
the belief that their company had enough resources
to acquire planning and data management systems;
the entrepreneurs with large companies agreed with
this statement (4.4) significantly more than entrepreneurs with small companies (3.4). Entrepreneurs
with small companies were significantly more posi-
96
Mean Likert value – Srednja Likertova vrijednost
Interest – Interes
Feasibility – Izvedivost
3.5
3.8
4.1
4.0
4.7
4.5
3.7
3.7
4.0
4.3
tive (4.5) that they had enough ability to use additional information technology than the entrepreneurs
with medium companies (3.6). The entrepreneurs
with large companies and the entrepreneurs with
four or five trucks were even more convinced (4.6
and 4.9, respectively) of their ability. The entrepreneurs with small companies were least likely (3.9)
and those with a large company were most likely
(4.8) to believe that the bargaining position of a regional entrepreneur would be stronger than under a
normal salary-based contract. This difference was
statistically significant. The entrepreneurs who worked for Other Customers believed significantly less
than the entrepreneurs who worked for »Stora Enso«
(3.4 and 4.8, respectively) that regional entrepreneurship would improve their bargaining position.
We investigated the interest of entrepreneurs in
various potential forms of co-operation and the perceived feasibility of that form, with the results pooled for all respondents (Table 2). Then we repeated
this analysis firstly for entrepreneurs grouped based
on their biggest customer (Fig. 3). The mean Likert
values ranged from 2.8 (not very interesting or feasible) to 5.3 (quite interesting and feasible). The entrepreneurs who worked for »Metsäliitto« were less interested in a joint venture for sales and marketing of
services (3.9) than other entrepreneurs. The differences were significant between »Metsäliitto« and
»Stora Enso« (5.2) and between »Metsäliitto« and
Other Customers (5.3). The entrepreneurs who worked for »UPM« evaluated company acquisition as less
feasible (3.8) than other entrepreneurs. The differences were statistically significant between »UPM«
and the Finnish »Forest and Park Service« (5.3) and
between »UPM« and »Metsäliitto« (4.9). Entrepreneurs who worked for »UPM« also considered merger to be less feasible (3.1) than other entrepreneurs,
and the difference between »UPM« and the Finnish
»Forest and Park Service« (4.4) was statistically significant. There was a significant correlation in the interest towards merger and company acquisition (t =
Croat. j. for. eng. 33(2012)1
Potential Mechanisms for Co-operation between Transportation Entrepreneurs and Customers ... (89–103) T. Palander et al.
Fig. 3 Attitudes of entrepreneurs towards various forms of consortium. Entrepreneurs were divided into groups based on their most important customer (I = interesting; F = feasible). 1 = Not at all interesting/feasible; 2 = Not interesting/feasible; 3 = Not very interesting/feasible; 4 = Don’t know; 5 = Quite interesting/feasible; 6 = Interesting/feasible; 7 = Very interesting/feasible
Slika 3. Stavovi poduzetnika prema razli~itim oblicima udru`ivanja. Poduzetnici su podijeljeni u grupe prema najva`nijim korisnicima (I = interesantno;
F = izvedivo). 1 = Uop}e nije interesantno/izvedivo; 2 = Nije interesantno/izvedivo; 3 = Nije jako interesantno/izvedivo; 4 = Ne znam; 5 = Prili~no interesantno/izvedivo; 6 = Interesantno/izvedivo; 7 = Jako interesantno/izvedivo
Fig. 4 Attitudes of transportation entrepreneurs with different company sizes towards various forms of consortium (I = interesting; F = feasible). 1 = Not at all
interesting/feasible; 2 = Not interesting/feasible; 3 = Not very interesting/feasible; 4 = Don’t know; 5 = Quite interesting/feasible; 6 = Interesting/
feasible; 7 = Very interesting/feasible
Slika 4. Stavovi poduzetnika u prijevozu drva s razli~itom veli~inom poduze}a prema odre|enim oblicima udru`ivanja (I = interesantno; F = izvedivo).
1 = Uop}e nije interesantno/izvedivo; 2 = Nije interesantno/izvedivo; 3 = Nije jako interesantno/izvedivo; 4 = Ne znam; 5 = Prili~no interesantno/izvedivo; 6 = Interesantno/izvedivo; 7 = Jako interesantno/izvedivo
0.433) and in the feasibility of these alternatives (t =
0.402).
We performed the same analysis, but this time
based on company size (Fig. 4). All company sizes
ranked a joint venture for sales and marketing as the
most interesting alternative. Small companies also
Croat. j. for. eng. 33(2012)1
considered this option to be the most feasible, but
large companies ranked it in third place in terms of
feasibility, with subcontracting and company acquisition ranked higher. Medium companies thought
that joint venture and joint venture for sales and
marketing were the most feasible alternatives. Small
97
T. Palander et al. Potential Mechanisms for Co-operation between Transportation Entrepreneurs and Customers ... (89–103)
companies were more interested in a merger (mean
Likert value = 4.0) than large companies (2.8), and
the difference was significant.
Table 3 summarizes the underlying factors responsible for the selection of the alternatives for each
group of customers. The entrepreneurs working for
»Stora Enso« were significantly less interested (mean
Likert value = 2.6) in expanding their company than
the entrepreneurs working for »UPM« (3.9). The entrepreneurs working for »Metsäliitto« (5.0) believed
that they had enough monetary resources to expand
their activities significantly more than entrepreneurs
working for Other Customers (3.3). Entrepreneurs
working for Other Customers believed that expanding their company would require hiring of additional staff for supervision and planning duties (5.9)
significantly more than those who worked for the
Finnish »Forest and Park Service« (4.8).
Table 3 also summarizes the responses to the
same questions, but grouped by company size. Almost all respondents thought (mean Likert value =
6.2) that there will be a shortage of drivers in the near
future. Some entrepreneurs noted that this was al-
ready a problem that limited expansion of their company. Respondents were most negative about their
willingness to expand their company (3.1) and about
whether increasing the company’s size would increase their profitability (2.6). The small and medium companies (2.5 and 2.3, respectively) rated this
probability lower than large companies (3.3), and the
difference was significant between the large and medium companies. The willingness to expand received a mean ranking of 2.9 for the small and medium
companies, versus 3.7 for the large companies. The
entrepreneurs were neutral about whether they were
interested in co-operation with harvesting entrepreneurs (4.0, 3.9 and 4.6 for small, medium and large
companies, respectively). However, some entrepreneurs in each size group were very interested in this
option. Respondents with medium companies believed that expanding their company would require
hiring additional staff for monitoring and planning
duties more (5.9) than those with small or large company (5.1), and the difference was statistically significant between the small and medium companies.
Those with small and medium companies were less
positive that better routing and backhaul planning
Table 3 Levels of agreement with statements that explained the choice of a form of consortium. 1 = Fully disagree; 2 = Disagree; 3 = Mildly disagree; 4 =
Don’t know; 5 = Mildly agree; 6 = Agree; 7 = Fully agree. Entrepreneurs were divided into groups based on their company size (Small (1 truck) = S; Medium (2 trucks) = M; Large (3 or more trucks) = L) and their most important customer (»Stora Enso« = A; »UPM« = B; »Metsäliitto« = C; »Forest and Park Service« = D; Other Customers = E)
Tablica 3. Razina slaganja s tvrdnjama koje obja{njavaju izbor oblika konzorcija. 1 = Uop}e se ne sla`em; 2 = Ne sla`em se; 3 = Blago se ne sla`em; 4
= Ne znam; 5 = Blago se sla`em; 6 = Sla`em se; 7 = Potpuno se sla`em. Poduzetnici su podijeljeni u grupe prema veli~ini tvrtke (Mali /1 kamion/ = S;
Srednji /2 kamiona/ = M; Veliki /3 ili vi{e kamiona/ = L) i najva`nijim korisnicima (»Stora Enso« = A; »UPM« = B; »Metsäliitto« = C; »[umska i park
slu`ba« = D; Ostali korisnici = E)
Customer – Korisnik
I have considered selling my company to someone who is expanding their activities
Razmatrao sam prodaju svoje tvrtke nekomu tko pro{iruje aktivnosti
I am willing to expand my company – Voljan sam pove}ati svoje poduze}e
I have enough monetary resources to expand my activities (savings or ability to obtain a loan)
Imam dovoljno nov~anih resursa da pro{irim svoje aktivnosti (u{te|evina ili mogu}nost dobivanja zajma)
There will be a shortage of drivers in the future – U budu}nosti }e nedostajati voza~a
I am interested in co-operation with harvesting entrepreneurs
Zainteresiran sam za suradnju s poduzetnicima na pridobivanju drva
An increase in the size of the company will also increase its profitability
Pove}anje veli~ine poduze}a tako|er }e pove}ati njegovu profitabilnost
Expanding my company will require the hiring of additional staff for supervision and planning duties
Pro{irenje }e poduze}a zahtijevati unajmljivanje dodatnoga osoblja za poslove nadzora i planiranja
Improving efficiency will let me hire additional staff
Pobolj{anje }e mi u~inkovitosti omogu}iti unajmljivanje dodatnoga osoblja
Better routing and backhaul planning will save money
Bolje odre|ivanje ruta i planiranje prijevoza u{tedjet }e novac
98
Company size
Veli~ina tvrtke
S
M
L
A
B
C
D
E
3.3
3.8
4.2
2.9
3.6
3.4
4.6
2.8
2.6
3.9
3.0
2.9
2.7
2.9
2.9
3.7
4.5
4.3
5.0
5.0
3.3
4.4
3.8
4.8
6.0
6.5
6.4
6.5
6.3
6.2
6.3
6.1
4.6
3.8
5.0
4.3
4.1
4.0
3.9
4.6
2.8
2.4
3.2
2.1
2.6
2.5
2.3
3.3
5.5
5.1
4.8
4.8
5.9
5.1
5.9
5.1
4.0
3.8
4.3
3.4
4.3
3.8
4.2
4.1
5.1
4.9
5.1
4.6
4.7
4.4
5.3
5.4
Croat. j. for. eng. 33(2012)1
Potential Mechanisms for Co-operation between Transportation Entrepreneurs and Customers ... (89–103) T. Palander et al.
would reduce their costs (4.4 and 5.3, respectively)
than entrepreneurs with large companies (5.5), and
the difference between the small and large companies was significant. The entrepreneurs with medium companies had thought about selling their
company more often (4.6) than other entrepreneurs
(3.4 for small company and 2.8 for large companies),
and the difference between the medium and large
companies was significant.
4. Discussion – Rasprava
Concerning the main objective of investigation –
how to develop co-operation between the transportation entrepreneurs and to facilitate outsourcing in
forest industry, the important aims were to learn
what factors are preventing regional entrepreneurship from becoming more common. It seemed that
nothing happened since 2005 that could be interpreted as increase of outsourcing (Fig. 1). Therefore,
this study is timely and relevant. An important obstacle was the lack of information about the plans of
the entrepreneur’s most important customer with
respect to regional entrepreneurship. Some entrepreneurs believed that their customer had kept them
poorly informed about the company’s plans, and
that the customer’s attitude towards regional entrepreneurship was unclear. In this context, it is important to remember that regional entrepreneurship is a
form of extended entrepreneurship (i.e., increased
transportation responsibilities) that is often part of a
company’s outsourcing strategy. Despite the bad reputation of outsourcing, general attitudes towards
this strategy can still be positive if entrepreneurs understand the situation and are confident that their
customers will support them through the transition
to the regional entrepreneurship.
Transportation entrepreneurs had similar views
about many statements regarding regional entrepreneurship. Most perceived that regional entrepreneurship was only a way to transfer the customer’s planning duties, management responsibilities, and costs
to entrepreneurs without providing adequate compensation. This view is a major, previously unremarked obstacle to the development of regional entrepreneurship because even entrepreneurs whose
customers were promoting regional entrepreneurship believed that the goal was to shift these burdens
to the entrepreneur. It also seems that wood-procurement organizations that have begun applying
regional entrepreneurship are working similarly to
how they used to work before adopting this approach; for example, they still define how entrepreneurs should manage their operations instead of
leaving the choice to the entrepreneur. Most entreCroat. j. for. eng. 33(2012)1
preneurs who responded to our survey wanted to
manage their routing and inventory control planning as well as negotiating pay rates from a position
of more power by forming a bigger consortium. Although materials-related functions related to the flow
of wood have been developed by forest industry, our
results suggest that the monetary chains and the information chains must be developed further because
of their importance to an entrepreneur’s business
operations. According to Beimborn et al. (2005) the
monetary chain is rarely designed and optimized to
provide a competitive advantage on its own because
it is usually a secondary process to support a material chain.
Another obstacle to the development of regional
entrepreneurship involves the difficulty of co-operation between entrepreneurs. Our results suggest that
it will be necessary to develop an operational environment in which business networks are in place
that let entrepreneurs simultaneously compete and
cooperate in dynamic entrepreneurial environment.
These aspects of co-operation have been important
targets of research, where operating models have
been developed to meet the management needs imposed by networking (Bengtsson and Kock 2000;
Bititci et al. 2005; Bertolini and Giovannetti 2006;
Jack et al. 2008). However, this approach remains unknown in the regional entrepreneurship of wood
transportation sector although customers are operating successfully.
Regional entrepreneurship was not expected to
improve the bargaining position of wood suppliers.
In the current economic situation, with increasing
global competition, this form of entrepreneurship
was seen as a possible way to survive, although the
entrepreneurs were generally more interested in the
pay-rate policies of their customers than in regional
entrepreneurship. Almost all entrepreneurs mentioned an imbalance between pay rates and transportation costs as a serious obstacle to the development of
regional entrepreneurship. In addition, many respondents described their current economic situation
as unsustainable. This is quite understandable given
that our study was conducted in 2006, when the
profitability of the Finnish forestry sector was poor
because of rapidly rising fuel prices and a strike that
affected many paper mills. In addition, the recession
and a delay in the education of truck drivers also reduced profits.
We found that entrepreneurs with four or five
trucks were most content with their situation, and
this group regarded regional entrepreneurship more
positively than any other group. Although differences between this company group and other large
companies were not statistically significant, this
99
T. Palander et al. Potential Mechanisms for Co-operation between Transportation Entrepreneurs and Customers ... (89–103)
group believed more in their skills and opportunities. Entrepreneurs who owned four or five trucks
also believed more often than any other group that
the growth of their company would increase profitability, but at the same time, they were more reluctant to expand their company size than entrepreneurs of other large companies. These results appear
to be contradictory, but the results can be explained
by the results of Soirinsuo and Mäkinen (2009), who
calculated that the most profitable company size in
Finland was five or six trucks, after which the
growth of the company did not seem to improve
profitability. It is possible that entrepreneurs with
four or five trucks saw that growth had been profitable up to their current company size, but feared that
future growth would require investments that were
bigger than the expected revenues. In theory they
would rearrange transportation functions if the costs
of internal transactions were less than the value of
what is gained by networking as suggested by Coase
(1992). On the other hand, it follows that if entrepreneurs can lower internal transaction costs, there will
be more rearrangements, and the wood procurement
network will become more productive.
Companies with two trucks seemed to be a problematic size. These entrepreneurs were least interested in expanding their company and least likely to
believe that growth of the company would improve
their profitability. These entrepreneurs believed most
commonly that the forest industry was only promoting regional entrepreneurship as a way to transfer
wood-procurement costs to the transportation entrepreneurs and that it would become necessary to hire
additional staff for management of their operations.
Owners of these companies had also more often considered selling their company than other entrepreneurs, and they had more doubts about their abilities
and as to whether their resources were sufficient to
permit growth. It seems that two trucks are insufficient to provide economies of scale, and that to grow,
these entrepreneurs would have had to change their
operation models by hiring additional staff. However, this change increases internal transaction costs
of the transportation company (Fig. 2). Later it may
also increase external transaction costs of wood procurement company, which may be considered as a
conflict of outsourcing (Williamson 1975, 1985; Coase
1991). For wood procurement network, it appears to
be more difficult to achieve good profitability simply
by increasing the workload of the entrepreneur, as
can be done in one-truck family enterprises. This became evident from the total volume of wood carried
by the transportation entrepreneurs, because the
productivity (m3/h) per vehicle of two-truck compa-
100
nies seemed to be lower than that of one-truck family
enterprises.
Regional entrepreneurship has been applied in
wood harvesting of wood procurement network during the last decade. We found that the transportation
entrepreneurs were interested in co-operation with
wood harvesting entrepreneurs. These were entrepreneurs with large transportation companies. However,
most entrepreneurs felt they lacked the skills they
would require to manage a company that would take
care of both wood harvesting and transportation. This
problem could be solved by forming a consortium
that combined the talents of an entrepreneur with
harvesting skills with the talents of one with transportation skills. Otherwise, wood suppliers’ role could
even be given to harvesting entrepreneurs who would
be responsible for large areas of wood procurement.
In this entrepreneurial environment transportation
entrepreneurs could operate as sub-contractors of
harvesting entrepreneurs as suggested in Fig. 2.
We also wanted to learn how interested entrepreneurs would be in forming various kinds of consortia and their perceptions of how feasible these alternatives would be. The alternatives that we proposed
were not especially interesting or perceived as easily
feasible to the entrepreneurs, though opinions varied. The best alternative appeared to be a joint venture for sales and marketing of services. This joint
venture would sign contracts with customers, and
then each shareholder would sign their own contract
with the joint venture. All monetary transactions
would be based on invoicing for services rather than
on salaries. This was the only alternative that was
not opposed by any group of transportation entrepreneurs. The result indicated that invoicing encapsulated in the financial chain should be addressed in
outsourcing as an autonomous source of competitive
advantage, as suggested by Beimborn et al. (2005).
There was also a statistically significant correlation
between interest towards mergers and interest towards company acquisitions. On the other hand,
there was a significant correlation between the interest in and perceived feasibility of the various consortium alternatives. This is obvious, because when entrepreneurs were interested in some form of consortium, they also saw it as a feasible alternative or at
least as more feasible than other alternatives in the
current working environment. It is good to note that
this survey established the current performance status (»gap«) being provided based on the operational-level entrepreneurs’ opinions. In future, this
strategic analysis could be continued using the collected benchmarks of SKAL.
It is noteworthy that two groups of entrepreneurs
were more interested in forming a joint venture reCroat. j. for. eng. 33(2012)1
Potential Mechanisms for Co-operation between Transportation Entrepreneurs and Customers ... (89–103) T. Palander et al.
sponsible for sales and marketing of their services
than was the case for two other groups of entrepreneurs. One group of entrepreneurs was more interested in a company acquisition and also believed
more strongly than other entrepreneurs that they
had the financial resources to expand their company.
One reason for the lack of interest in forming consortia was the long work week. On average, an entrepreneur worked almost 70 hours per week, and in
some cases, more than 100 hours. Clearly, the work
week is too long for the well-being of entrepreneurs,
and this may explain why most entrepreneurs were
not interested in expanding their company: they
feared the possibility of further increases in their
work week. On the other hand, subcontracting was
not an interesting alternative either for the small and
medium companies, so it is understandable that selling the company was a more interesting alternative
for these entrepreneurs. In the future, more research
will be needed to develop an operational environment in which increasing company size is an attractive option.
Opinions about co-operation reflected the views
of entrepreneurs who had not yet adopted regional
entrepreneurship. These entrepreneurs are the group
with the most potential for the development of improved co-operation between wood suppliers and
their customers. These entrepreneurs are described as
institutions or transportation companies in the transaction model (Fig. 2). The results indicated that only
the first steps have been taken towards outsourcing,
because practical details about the forms of consortia
are still unclear. This was also revealed by comparing
the present results with those of theoretical studies of
co-operation and its objectives by Högnäs (2000). For
example, transportation entrepreneurs whose biggest
customer was »Metsäliitto« and those whose biggest
customer was »UPM« had different conceptions of
the effects of regional entrepreneurship on cost effectiveness of the wood-procurement network and on
the profitability of the transportation operation. As
they understood co-operation differently, it will be
necessary to propose consistent developmental decisions to ensure that both groups of entrepreneurs
have the same understanding.
A joint venture that focuses on sales and marketing could be a way to promote the development of
outsourcing by awarding larger contracts than are
currently awarded and larger transportation functions thereby giving entrepreneurs an incentive to
increase their operational capacity and giving entrepreneurs more freedom of action. Before drawing
further conclusions about this possibility, more studies will be necessary to confirm, for example, whether this form of organization can be developed and
Croat. j. for. eng. 33(2012)1
understood by entrepreneurs, and how the coordinator of such an organization would manage the chains
of materials, money, and information required to support transactions of the transportation function
(Palander et al. 2006).
5. Conclusions – Zaklju~ci
The results of the present study suggest that external reorganization of the truck transportation sector and internal structural changes in transportation
entrepreneurship are currently underway, but that
the objectives of these changes are unclear for all
stakeholders in the wood-procurement network. To
facilitate the development of co-operation in the wood
transportation, the objectives of co-operation should
be determined quickly and communicated to all stakeholders. The challenge for transportation entrepreneurs is to find the best set of interconnected service solutions that meet the strategic needs of wood
procurement network. Those who are considering
outsourcing of the transportation function must be
aware of the linkage between reducing the staff in
wood-procurement organizations and reorganizing
the wood transportation sector, and the effect of the
resulting operating environment on opportunities
for co-operation.
For better environment the entrepreneurs felt that
the most interesting form of consortium between
suppliers, which would let them respond better to
outsourcing, would be the formation of a joint venture responsible for sales and marketing of their services. Such a company would develop an overall
contract with each customer, and then each shareholder in the joint venture would sign their own contracts with the venture to share the work. All transactions would be based on invoicing instead of the
current salary-based approach. However, entrepreneurs did not believe that their profitability would
increase by expanding their company size in the current entrepreneurial environment. To conclude, if
the aim of co-operation is to outsource the wood
transportation function, decision-makers in the Finnish forest industry should modify the current environment so that larger, more organized consortia of
wood suppliers would become more profitable than
they presently are.
Acknowledgement – Zahvala
Authors are grateful to »Metsämiesten Säätiö«
for funding. We also thank all the entrepreneurs who
participated in our study, and Kari Palojärvi, Director of the Timber Carriers Association, for making
this study possible.
101
T. Palander et al. Potential Mechanisms for Co-operation between Transportation Entrepreneurs and Customers ... (89–103)
6. References – Literatura
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Bengtsson, M., Kock, S., 2000: »Coopetition« in business
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Bertolini, P., Giovannetti, E., 2006: Industrial districts and
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Bititci, U. S., Mendibil, K., Martinez, V., Albores, P., 2005:
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Sa`etak
Mogu}i mehanizmi suradnje poduzetnika i korisnika prijevoza drva:
studij slu~aja regionalnoga poduzetni{tva u Finskoj
Gotovo sve drvo kori{teno u finskoj {umskoj industriji u nekoj se fazi, unutar mre`e dobavljanja drva od {ume
do pilana i tvornica, transportira kamionima. Trenuta~no otprilike 850 finskih tvrtki za transport drva posjeduje
oko 1700 kamiona i zapo{ljava oko 2600 voza~a. Tri su ~etvrtine od tih poduzetni~kih tvrtki za prijevoz drva mala
poduze}a; obitelji posjeduju jedan ili dva kamiona, koji obi~no vi{e od 90 % drva dostavljaju samo jednomu
korisniku. Danas, u podru~ju dobavljanja drva, s ukupnim udjelom od 90 % drva koje se transportira u Finskoj,
prevladavaju tri najve}a korisnika (»Stora Enso«, »UPM«, i »Metsäliitto«).
Tradicionalno takve organizacije za dobavljanje drva potpisuju izravne ugovore o prijevozu sa svakom od tvrtki
za transport drva. Takvi su ugovori kori{teni da se strogo definiraju prijevozni~ki poslovi za koje su poduzetnici
odgovorni. Uobi~ajeno, ve}ina je tih ugovora bila sklopljena sa zaposlenicima organizacija za dobavljanje drva i odre|ivala je fiksnu pla}u za voza~a kamiona. Nedavno je {umska industrija u nastojanjima da smanji svoje operativne tro{kove zapo~ela s poku{ajima da mnoge djelatnosti, uklju~uju}i i prijevoz drva, izdvoji iz svoga poslovanja.
Ipak, taj je prijelaz samo djelomi~no ostvaren, te sada{nji oblik poduzetni{tva u prijevozu drva jo{ uvijek zadr`ava
mnoga obilje`ja tradicionalnoga sustava u transportu drva. U provedenom se istra`ivanju poduzetnici na
prijevozu drva smatraju isporu~iteljima drva, a organizacije za dobavljanje drva u {umskoj industriji predstavljaju
njihove korisnike, odnosno korisnike usluga transporta drva.
102
Croat. j. for. eng. 33(2012)1
Potential Mechanisms for Co-operation between Transportation Entrepreneurs and Customers ... (89–103) T. Palander et al.
U ovom promjenjivom poslovnom okru`enju {umska industrija nastoji unaprijediti vlastitu tro{kovnu u~inkovitost tako da privatnim prijevoznicima drva nudi sporazume o pro{irenom poduzetni{tvu kojima se pove}avaju
njihove odgovornosti. Zapravo, pro{ireno je poduzetni{tvo prva faza u zapo~etom procesu prijelaza od ugovornoga
modela u mre`i dobavljanja drva ka modelu izdvajanja transporta u mre`i isporu~ivanja drva.
Za finsku {umsku industriju takvo je pro{ireno poduzetni{tvo logi~na posljedica izdvajanja poslovnih funkcija
koje nisu vezane uz temeljnu djelatnost poduze}a (outsourcing), postupak koji na me|unarodnim tr`i{tima postaje
sve vi{e uobi~ajen. Na temelju teorije o poslovnim tro{kovima izdvajanje prijevoza drva mogli bi se smanjiti ukupni
tro{kovi dobavljanja sirovoga materijala do tvornice. Ako je ta teorija to~na, unaprijedila bi se ukupna tro{kovna
u~inkovitost i me|unarodna konkurentnost {umske industrije.
Regionalno je poduzetni{tvo jedan od oblika pro{irenoga poduzetni{tva u kojem se naglasak stavlja na suradnju
isporu~itelja drva (poduzetnika) i korisnika prijevoza drva. U sektoru transporta drva regionalno je poduzetni{tvo
relativna novost, iako su poduzetnici na prijevozu zemlje i gradnji cesta primjenjivali takav pristup ve} desetlje}ima. U primjeni tipi~noga regionalnoga poduzetni{tva organizacije za dobavljanje drva potpisale bi ugovore o
prijevozu s manjim brojem poduzetnika, od kojih je svaki odgovoran za ve}e podru~je (regiju). Takvi bi pro{ireni
ugovori uklju~ivali prijevozni~ke zadatke koji su ve}i i raznolikiji, u {to je uklju~eno i vi{e odgovornosti nego u
klasi~nim ugovorima. Regionalni poduzetnik mo`e ispuniti svoje ugovorne obveze rade}i sam ili u suradnji s drugim poduzetnicima. Navedeni se oblik suradnje mo`e ostvariti kroz razli~ite na~ine udru`ivanja: podugovaranjem
poslova, zajedni~kim poslovnim pothvatima i ulaganjima, spajanjem poduze}a, kupnjom poduze}a.
Regionalno poduzetni{tvo korisnici prijevoza drva sporo prihva}aju. Me|utim, dok odre|eni korisnici tek po~inju istra`ivati ugovore s pro{irenim poduzetni{tvom, pojedini su korisnici s poduzetnicima ve} potpisali takve
ugovore. Ispitivanja pokazuju da se promicanje regionalnoga poduzetni{tva i izdvajanje prijevoza mo`e posti}i
pove}anjem veli~ine ugovora, pro{iruju}i broj zadataka i odgovornosti uklju~enih u ugovor, te davanjem poduzetnicima vi{e slobode u njihovim aktivnostima. U transportu drva takvi postupci zahtijevaju suradnju poduzetnika
u osnivanju konzorcija, koji potencijalno mogu biti profitabilniji.
Ciljevi su provedenoga istra`ivanja bili da se ispitaju na~ini na koje je mogu}e pobolj{ati suradnju u pristupu
regionalnoga poduzetni{tva u transportu drva i da se olak{a zapo~eti proces izdvajanja odgovornosti u dobavljanju
drva u finskoj {umskoj industriji. Ispitana je suradnja izme|u poduzetnika na prijevozu (isporu~itelji drva) te
izme|u poduzetnika i {umske industrije (korisnici prijevoza). Poduzetnicima u prijevozu drva koji rade unutar
mre`e dobavljanja drva korisnika poslan je upitnik. Poduzetnici smatraju da najzanimljiviji oblik konzorcija
prijevoznika drva, koji im mo`e omogu}iti bolji odgovor na regionalno poduzetni{tvo i vanjsko ugovaranje
prijevoza (outsourcing), predstavlja formiranje zajedni~kih pothvata i ulaganja u prodaji i marketingu njihovih
usluga. Takva bi tvrtka razvila sveobuhvatni ugovor sa svakim korisnikom, zatim bi svaki sudionik u takvu
ulaganju/pothvatu potpisao vlastiti ugovor sa zajedni~kom tvrtkom radi raspodjele poslova. Sve bi se transakcije
temeljile na fakturiranju umjesto sada{njega pristupa na osnovi pla}a. Ipak, poduzetnici ne vjeruju da }e se u
postoje}em poduzetni~kom okru`enju pro{irenjem njihovih odgovornosti pove}ati njihova profitabilnost. Ako je cilj
suradnje izdvajanje transporta drva, donositelji odluka u finskoj {umskoj industriji trebaju promijeniti sada{nje
okru`enje tako da ve}i i organiziraniji konzorciji poduzetnika koji prevoze drvo postanu profitabilniji nego {to to
trenuta~no jesu u pristupu regionalnoga poduzetni{tva.
Klju~ne rije~i: dobavljanje drva, outsourcing, regionalno poduzetni{tvo, umre`avanje i povezivanje
Authors’ address – Adresa autorâ:
Received (Primljeno): July 17, 2011
Accepted (Prihva}eno): November 21, 2011
Croat. j. for. eng. 33(2012)1
Prof. Teijo Palander, PhD.
e-mail: teijo.s.palander@uef.fi
Mika Vainikka, MSc.
e-mail: mika.vainikka@uef.fi
Antti Yletyinen, BSc.
e-mail: antti.yletyinen@student.uef.fi
University of Eastern Finland
Faculty of Science and Forestry
Joensuu Campus
Yliopistokatu 2
P.O. Box 111
FI-80101 Joensuu
FINLAND
103
Original scientific paper – Izvorni znanstveni rad
The Present State and Prospects
of Slovenian Private Forest Owners’
Cooperation within Machinery Rings
[pela Pezdev{ek Malovrh, Petra Gro{elj, Lidija Zadnik Stirn, Janez Kr~
Abstract – Nacrtak
The study analyzes the challenges and prospects of private forest owners’ cooperation based
on the use of machinery in Slovenia applying the strengths, weaknesses, opportunities and
threats approach (SWOT analysis) in combination with the analytic hierarchy process
(AHP). The data from questionnaires with forest owners and presidents of machinery rings
were used to develop and to analyze the strategies for forest owners’ cooperation. The results
reveal that the members of machinery rings are only partly satisfied with the operation of the
existing rings and that the activities of rings meet the members’ interests related to forest
management. Thus, machinery rings are recognized as a suitable form of forest owners’ cooperation. The presidents of machinery rings perceive the integration of farmers and private
forest owners, as well as knowing the level of mechanization of members as major strengths
of machinery rings. Further, strengthening the operation of machinery rings in the field of
forestry is recognized as an important opportunity. The shortage of means for operation is
identified as a weakness for machinery rings, and the lack of subsidies for investments in
equipment is identified as a critical threat. However, the rank of importance of the SWOT
groups leads to defensive approach in the strategic planning where machinery rings have to
minimize weaknesses in order to avoid threats. These results provide important insights in
the future development of forest owners’ cooperation based on common use of machinery.
Keywords: cooperation based on the use of machinery, machinery rings, private forests, survey,
A’WOT method, strategic planning
1. Introduction – Uvod
Renewable natural resources, wood being among
the most important ones, are limited and their availability depends on terrain and climate circumstances/conditions, on the technological development
and its application in forest management. Slovenia
maintains close-to-nature forestry, which incorporates two main principles: sustainability of all forest
functions and imitation of natural processes (Sustainable Forest Management). This principle demands
for a significant incorporation of the social component into forest management activities.
In Slovenia small-scale private forests are dominant as 73% of forests are privately owned (Report of
the Slovenian Forest Service 2010). The property structure of Slovenian privately-owned forests reveals
that 58.4% of owners have a forest property smaller
Croat. j. for. eng. 33(2012)1
than 1 ha and that the average property size of private forests is less than 3 ha (Pezdev{ek Malovrh et
al. 2010).
The development of small-scale private forestry
and management activities are strongly connected to
socio-economic structural changes of the population,
which are related to an increasing number of owners
and to the diminishing in size of forest properties as
well as a decrease of rural population (Pezdev{ek
Malovrh 2006, Stampfer et al. 2001). These changes
result in the absence or insufficient forest management, inefficient equipment and inadequate qualification for work, as well as in low profitability (Lahdensaari 2001).
The consequences of such management practices
are reflected in the lack of exploitation of natural
resources as only two thirds of the potential timber
removal in Slovenian private forests is implemented
105
[. Pezdev{ek Malovrh et al.
The Present State and Prospects of Slovenian Private Forest Owners’ Cooperation ... (105–114)
and according to forest management plans, less than
half of silvicultural work is carried out (Report of the
Slovenian Forest Service 2010).
According to Stampfer et al. (2001) insufficient
use of machinery and improvement of harvesting
system were recognized as significant management
problems in small-scale forests in Austria. The situation in Slovenia is quite similar, and in some respects
the private forest management reveals additional
and extended problems. Slovenia is faced with the
problem of overcapacity of mechanization in agriculture and forestry. Based on the number of tractors
per capita, Slovenia is in the leading position worldwide (followed by Ireland in the second place and
Austria in the third place). Consequently, compared
to Austria, Slovenia also deals with management problems, where the modernization of equipment, an
adequate procurement of technical means (machinery), a rational investment and expansion of fully-mechanized machines are of key importance for
management improvement.
Modern forestry mechanization offers the benefits such as multiplying operator productivity (Spinelli and Magagnotti 2010) and enhancing work safety (Bell 2002), but on the other hand requires a significant capital investment, which often exceeds the
capacity of small-scale private forest owners (Spinelli and Magagnotti 2011). So, on the one hand, technological progress depends upon the conditions and
trends in individual households and, on the other
hand, on financial incentives (Robek et al. 2005).
In order to ensure the exploitation of machinery
capacity, cooperation between owners has to be developed based on the use of machinery. The use of
modern technology in small-scale forestry is only
possible by cost rationalization in mechanization.
Therefore, it is necessary for private forest owners to
cooperate based on the use of machinery in order to
increase their competitiveness.
In the first phase, the aim of this paper is to
establish the present state of cooperation, using a
survey, based on the use of machinery in Slovenia,
and in the second phase to find a hinge between the
existing situation and future strategies of forest owner cooperation regarding the machinery in Slovenia
by the use of A’WOT method.
2. Cooperation of forest owners
regarding the use of machinery
in Slovenia – Suradnja {umovlasnika
u upotrebi mehanizacije u Sloveniji
The existing forest owners cooperation based on
the use of machinery in Slovenia, such as machinery
106
rings and machinery communities, is essential to
give small-scale private forest owners the chance to
overcome the cost inefficient forest management and
use the advantages of modern technologies.
»Machinery« rings are an organized form of
»neighbor assistance« and voluntary association of
farmers and private forest owners in the region operating on a group basis. Cooperation based on the
use of machinery is extended to the whole area of a
machinery ring. Its members offer free capacity of
the machinery or labor to other members through
their work and use of their own machinery or lend it
without an operator, but the member has to pay a
price covering the machine costs. It is the responsibility of machinery rings to inform members and to
provide them services. In the legal, tax and financial
terms, the services are carried out directly between
the client and the contractor.
The first machinery rings were established in Slovenia in 1994. So far 45 machinery rings have been
established. Nowadays, they practically cover the
whole country. At the end of 2010 they had 6,018
members. The Societies Act (2011) forms the legal
basis for machinery rings. Machinery rings are mainly engaged in agriculture; only three of them are
engaged in forestry. In the previous year (2010), the
members carried out on average about 140,000 hours
of services, which represents approximately 23 hours
of services per member (Dolen{ek 2008).
The economic benefits of participation in the
machinery rings are higher utilization of machines
and a consequent reduction of costs, higher productivity and quality of work, as well as the possibility to generate additional income by working in
other members’ farms or forests. Furthermore, the
social benefits of participation in machinery rings
are connected to work safety and consequently to
reducing the number of accidents, to participation
and offering help in labor during the holidays and
peak seasons, to improved social relationship between neighbors, all resulting in improved quality of
life on the farm.
The main feature of machinery communities is a
combined purchase of machinery and equipment.
The investment is distributed among several farms,
which are community members. They mostly buy
machinery or equipment that is used only a few days
per year or has a high capacity and high costs (Plej
2001).
Most machinery communities are formed based
on a verbal agreement between neighbors that are
farmers or/and forest owners to purchase machinery
or equipment and each member pays a share proportional to the size of his farm or forest. On the other
hand they can also sign a contract for establishing a
Croat. j. for. eng. 33(2012)1
The Present State and Prospects of Slovenian Private Forest Owners’ Cooperation ... (105–114)
machinery community where they define the value
of the machinery, the share of each member, the order for machinery use, the possibilities for switching
the order, the storage of machinery, its maintenance
and maintenance costs (Zgonjanin 1987).
Community machinery is used by members in a
predetermined order, but for the most complex pieces
of machinery, members can agree that only the most
qualified member of the community can operate the
machine. In this particular case, the members agree
on the manner of compensation costs for the work
done, mostly with money or their own labor (Ekart
1978, Oto 2011).
A joint purchase and use of machinery have many
advantages compared to individual purchase and
use. It provides the opportunity to buy modern machines and reduces the possibility of buying obsolete
machinery, the maintenance of which tends to be
expensive ([umi 1977).
3. Methods used – Metode rada
3.1 Surveying private forest owners and data
analysis – Anketiranje privatnih
{umovlasnika i analiza podataka
The population sample consisted of private forest
owners that were members of machinery rings (n =
1471). The members were stratified into five property
size classes – strata (less than 1 ha; 1 – 5 ha; 5 – 10 ha;
10 – 30 ha; more than 30 ha). Sampling was systematically conducted within each of these five strata. In
total 172 members of machinery rings were selected
(Table 1). Prior to the study, the questionnaire was
tested on 7 forest owners. In the year 2009 face-to-face interviews were done with selected members. The overall response rate was 45.9% (n = 79).
The analysis of the frequencies of non-response showed no significant difference between property size
classes (c2= 4.000; p=0.406).
In the survey, respondents were asked which interests they fulfill as members of machinery rings,
whether they are satisfied with machinery rings, how
[. Pezdev{ek Malovrh et al.
the rings fulfill their expectations and if machinery
rings represent a suitable cooperation form in relation to forest owners’ needs in forest management.
They assessed the satisfaction and suitability on a
five point Likert scale, where one means very unsatisfied/unsuitable and five very satisfied/suitable.
The statistical analyses performed in this study were
based on frequency distribution across ordinal variables. Firstly, descriptive statistics and frequency
histograms for all variables were produced and then
the mean values considered.
3.2 A’WOT method – Metoda A’WOT
SWOT analysis is a strategic management tool
that helps to identify internal strengths and weaknesses and external opportunities and threats for
any organization, project or individual (Dyson 2004)
in order to attain a systematic approach and support
the decision situation (Pesonen et a. 2001). The most
important internal and external factors for the organizational future are referred to as strategic factors
and they are summarized within the SWOT analysis.
SWOT analysis can provide a good basis for successful strategy formulation (Kurttila et al. 2000,
Rauch 2007).
However, one of the main limitations of SWOT
analysis is that the importance of each factor in decision making cannot be measured quantitatively and
therefore, it becomes difficult to assess the potential
of a factor to influence strategic decision (Dwivedi et
al. 2009). Kurttila et al. (2000) examined a new hybrid method (A’WOT) where they integrated the
Analytic Hierarchy Process (AHP) within SWOT analysis, for improving the usability of SWOT analysis.
AHP (Saaty 1980) enables to assign a relative priority
to each factor through pairwise comparison, on a
scale where 1 implies equal, 3 moderate, 5 strong, 7
very strong and 9 extreme. From the pairwise comparisons the relative priority weight of each factor
within each SWOT groups is computed using the
eigenvector method as explained below.
According to Saaty (1980), information derived
from the pairwise comparisons is represented in a
Table 1 Distribution of population and sample according to strata
Tablica 1. Raspodjela populacije i uzorka {umovlasnika po razredima
Number of cases – Broj slu~ajeva
Population distribution – Raspodjela populacije
Sample distribution – Raspodjela uzorka
Response distribution – Raspodjela odgovora
Croat. j. for. eng. 33(2012)1
Less than 1
Manje od 1
469
19
1
Strata, ha – Grupe, ha
1 to 5
5 to 10
10 to 30
1 do 5
5 do 10
10 do 30
529
218
191
51
42
36
18
18
26
More than 30
Vi{e od 30
64
24
16
Total
Ukupno
1471
172
79
107
[. Pezdev{ek Malovrh et al.
The Present State and Prospects of Slovenian Private Forest Owners’ Cooperation ... (105–114)
comparison matrix A (1), where the comparison between i th and j th element enters into the matrix as an
element aij, and inverse comparisons as aij = 1/aij
é1
ê1
a 12
A=ê
êM
ê1
êë a 1n
a 12
1
M
1
a2 n
L a 1n ù
L a2 n ú
ú
O M ú
ú
L 1 ú
û
(1)
For deriving priorities, the eigenvector method is
used, where the priority vector w = (w1,..., wn) is
obtained by solving the equation Aw = lmax w,
Where:
lmax is the largest eigenvalue of the matrix A.
The comparison matrix A is consistent if its entries satisfy: aij ajk = aik, for all i, j, k = l,…,n.
Consistency ratio (2) measures the inconsistency
among the pairwise comparisons:
CR =
CI
RI
(2)
lmax - n
is the consistency index, n is
n -1
the order of matrix A and RI is the average random
consistency index. Regarding the consistency, the comparison matrix A is acceptably consistent if CR < 0.1,
but in the opposite case (CR > 0.1), serious inconsistencies may exist and the AHP may not yield meaningful results, so decision makers should reconsider
their judgments (Saaty 1980, [por~i} et al. 2010).
The final goal of a strategic planning process, of
which A’WOT analysis is an early stage, is to develop
and adopt a strategy (strategic objectives) resulting
in a good fit between the internal and external factors
and the goals of the forms of cooperation (Kangas
et.al 2003). There are two possible approaches, an
offensive approach and a defensive approach. The
»offensive approach« represents two possible combinations to the strategic development – the first one
being the use of strengths to take opportunities, and
the second the taking of opportunities by overcoming the weaknesses. Furthermore, the »defensive approach« also represents two combinations – to avoid
threats by using the strengths or minimizing the
weaknesses (Maru{i~ 2005).
Where CI =
3.2.1 Application of A’WOT method to private
forest management – Primjena metode
A’WOT u upravljanju privatnim {umama
In a first phase, the list of machinery rings in Slovenia was prepared working in different fields, from
agriculture to forestry. To identify the factors in each
SWOT group, the presidents of machinery rings that
108
work in the Slovenian forestry (n = 3) were interviewed. They were asked to express their opinion
about the strengths, weaknesses, opportunities and
threats of their activities in private forest management.
Based on the factors identified in each SWOT
group, a questionnaire was prepared. This questionnaire contained pairwise comparisons between all
factors in a particular SWOT group. Individual judgments were aggregated into a group judgment by
the geometric mean (Lai et al. 2002, Saaty 2003, Gro{elj and Zadnik Stirn 2011, [por~i~ et al. 2011). These
mean values form group comparison matrices and
weights (w) were obtained for each SWOT factor using eigenvector method. The factor with the highest
priority score was identified in each SWOT group. A
separate questionnaire containing pairwise comparisons between the factors with highest priorities
score in each SWOT group was developed. This was
done to estimate the overall priorities of different
SWOT groups.
As some individual comparison matrices were
not acceptably consistent, the respondents were asked to reconsider their judgments so as to get acceptably consistent group comparison matrices derived
from individual comparison matrices.
4. Results and discussion – Rezultati
i rasprava
4.1 Results of questionnaires – Rezultati
upitnika
The members of machinery rings are only partly
satisfied with the operation of the rings (average
value is 3.7). The members stated that they felt slight
dissatisfaction due to the inactivity of machinery
rings, lack of services offered, lack of cooperation
among members, difficulties in issuing accounts and
poor organization in machinery rings as machinery
rings do not make the list of services offered by
members or the list of machinery available to the
members. The results supply evidence for a need of
ongoing organizational changes in machinery rings.,
It is, therefore, necessary that the rings start being
professional in their operation as only a well-organized cooperation system is able to organize and
control the whole information and machinery needs.
Furthermore, in total 93.9% of private forest
owners meet the interests related to forest management in machinery rings. They highlighted 12 key
interests that they fulfill in machinery rings (Table 2)
that are connected to wood skidding, easier and
quicker completion of work, helping in harvesting,
education, excursions and demonstrations, and joint
Croat. j. for. eng. 33(2012)1
The Present State and Prospects of Slovenian Private Forest Owners’ Cooperation ... (105–114)
Table 2 Interests the members fulfill in machinery rings
Tablica 2. Interesi koje ~lanovi ispunjavaju u udru`enju za upotrebu
{umske mehanizacije
Interest – Interesi
Help in wood skidding – Pomo} pri privla~enju drva
Easier and quicker completion of work – Lak{e i br`e obavljanje
poslova
Help in harvesting – Pomo} pri sje~i
Education – Obrazovanje
Excursions and demonstrations – Izleti i prikazi
Joint purchasing of equipment – Zajedni~ka nabava opreme
Offering services with agricultural machinery to other members
Ponuda usluga poljoprivredne mehanizacije drugim ~lanovima
Getting information – Dobivanje informacija
Social help – Socijalna pomo}
Economic interest – Ekonomski interes
Excise duties – Tro{arine
Timber sale – Prodaja drva
Share, %
Udio, %
13.3
13.3
12.0
10.7
9.3
9.3
6.7
6.7
4.0
2.7
2.7
2.7
purchasing of equipment. Less often they fulfill the
interests that are related to timber sale, excise duties,
economical interest, social help and offering services
with agriculture mechanization to other members.
Nevertheless, the members are unable to sufficiently meet the following interests in machinery
rings: the production of wood chips, execution of silvicultural work, joint purchases of machinery, promotion of forest management intensification, forest
[. Pezdev{ek Malovrh et al.
products marketing and winter maintenance of forest roads.
For most members, machinery rings are a suitable form of cooperation in relation to their needs in
forest management (average value = 4.0). These
findings relate to the fact that the cooperation based
on the use of machinery will also be important in the
future, especially having in mind the socio-economic
changes from pure farms to mixed or supplement
farms. Consequently, less and less private forest owners will have the time, the practical experiences of
forest management and sufficient knowledge in forestry, and thus in future a greater share of private
forest owners will hire services offered by machinery rings. Therefore, the future public institution cooperation should be promoted based on the use of
machinery.
4.2 Results of A’WOT method – Rezultati
metode A’WOT
SWOT analysis involved three presidents of machinery rings that deal exclusively with forestry in
Slovenia. The results reflect the point of view of the
presidents and are presented in Table 3.
The strength of machinery ring is shown in the
association of farmers and private forest owners who
cooperate in the utilization of machinery, which is
not limited only to the closest neighbors (inter-neighbor assistance) but is available for use in the whole
area of the machinery ring (several villages, municipality). Furthermore, the head of the machinery ring
knows the mechanization of members, passes on the
information about needs and available capacities,
Table 3 SWOT analysis of machinery rings
Tablica 3. SWOT analiza udru`enja za upotrebu mehanizacije
STRENGHTS – SNAGE
Integration of farmers and private forest owners
Povezanost poljoprivrednika i privatnih {umovlasnika
Knowing the level of mechanization of members
Poznavanje razine mehanizacije kod ~lanova
Education of private forest owners
Obrazovanje privatnih {umovlasnika
OPPORTUNITIES – PRILIKE
Partial professionalization of work
Djelomi~na profesionalizacija rada
Strengthening the operation of the machinery rings in the field of forestry
Ja~anje operacija udru`enja u {umarstvu
Croat. j. for. eng. 33(2012)1
WEAKNESSES – SLABOSTI
Realization of personal interests
Postizanje osobnih interesa
Not enough means for operation
Nedovoljno sredstava za operacije
Lack of time of the machinery ring president
Nedostatak vremena predsjednika udru`enja za upotrebu mehanizacije
S W
O T
THREATS – PRIJETNJE
Competition among providers/members
Konkurencija me|u dobavlja~ima/~lanovima
Subsidies for equipment investments
Poticaji za nabavu opreme
Fostering the association of Slovenian public forestry service into other forms of
cooperation – Poticanje udru`ivanja u druge oblike suradnje koje dolazi od
javnoga {umarskoga servisa Slovenije
109
[. Pezdev{ek Malovrh et al.
The Present State and Prospects of Slovenian Private Forest Owners’ Cooperation ... (105–114)
and coordinates the collaboration of the clients and
service providers. The strength is also that the members are trained and educated in the ring – for example forest machinery rings are active especially in the
field of work safety in the forest, they attend machinery presentations, excursions, and courses.
As all forms of cooperation are organized as a society and are operating on voluntary basis, machinery rings also have to deal with weaknesses such as
personal interests of the members, poor financial
means for operation, which decreases on a yearly basis, and a lack of time of the people in charge. Machinery rings receive financial means mainly through
members’ fees, by co-financing by the Ministry of
Agriculture, Forestry and Food, and by charging its
services to non-members. Still, there is a lack of financial means to professionalize the position of the
executive of the machinery ring (in Slovenia one executive has a part-time job, the rest work under contracts) (Dolen{ek 2008). This implies that Governmental institutions (especially the Ministry of Agriculture, Forestry and Food) should become more
active in promoting cooperation in joint purchases
and use of machinery and in supporting efforts for
professionalizing such forms. However, a financial
system should be established that will in its initial
phase help machinery rings to start with semi professionalization and find a way to stimulate the employees of public institutions (e.g. possibilities for
additional education, involvement in forestry excursions) to spread information and to promote cooperation of common machinery use. Due to the operation expansion and an increase of members (between
2006 and 2009, membership grew from 330 to 460
with the area collectively owned by these members
similarly growing from 4.715 ha to 6.713 ha in three
forestry machinery rings), it is not surprising that
people in charge of machinery rings do not have
enough time to do their tasks. Hence, the status of
machinery rings must change.
As mentioned above, the work in machinery rings
should be professionalized, especially when a machinery ring gets enough members (more than 400)
and when it reaches a sufficiently wide range of services (Dolen{ek 2008). This is recognized as the main
opportunity for machinery rings. The opportunities
are also reflected in improved activities in the field of
forestry, especially with technological development
and improved harvesting system. With modern and
more highly mechanized forest machines, the investment costs increase. An increased need for machinery cooperation is expected in the future as these
modern logistic concepts require a significant capital
investment, which often exceeds the capacity of private forest owners, based on modest income from
110
their small-scale forests. On the other hand, in machinery rings, the employment of forest contractors
(one of the members) ensures forest tending, as small-scale private forest owners are insufficiently professionally, technically and financially skilled for the
management of forests.
If the members of a machinery ring provide the
same services, internal competition can occur, which
represents a threat for machinery ring operation.
Subsidies for investments into equipment and machinery purchase are given only to bigger owners.
This has an adverse effect on the owners with small-size properties but could nonetheless provide the
same services to the members in a machinery ring.
Obviously, the subsidies system should be changed
so as to enable the members of machinery rings to
apply for such subsidies provided that they undertake to work with such machinery in a machinery
ring for the next five years. Recently, there has been a
trend in the Slovenian public forestry service to stimulate the association of private forest owners into
societies. However, this has a negative effect on machinery rings and can also be seen as a threat.
To arrive to the final stage of A’WOT method, the
priority vectors (w) and consistency rations (CR) of
group comparison matrices were calculated for factors
in SWOT groups. They are presented in Tables 4–7.
Table 4 Priority vector and consistency ratio of group comparison matrix of strengths
Tablica 4. Vektor te`ine i omjer konzistencije za matricu usporedbe
snage
Strengths – Snage
Integration of farmers and private forest owners – Povezanost
poljoprivrednika i privatnih {umovlasnika
Knowing the level of mechanization of members – Poznavanje
razine mehanizacije kod ~lanova
Education of private forest owners – Obrazovanje privatnih
{umovlasnika
w
0.4844
0.4060
0.1095
CR=0.0347
Table 5 Priority vector and consistency ratio of group comparison matrix of weaknesses
Tablica 5. Vektor te`ine i omjer konzistencije za matricu usporedbe
slabosti
Weaknesses – Slabosti
Not enough means for operation – Nedovoljno sredstava za
operacije
Lack of time of the machinery ring president – Nedostatak
vremena predsjednika udru`enja za upotrebu mehanizacije
Realization of personal interests – Postizanje osobnih interesa
w
0.5821
0.2750
0.1430
CR=0.0003
Croat. j. for. eng. 33(2012)1
The Present State and Prospects of Slovenian Private Forest Owners’ Cooperation ... (105–114)
Table 6 Priority vector and consistency ratio of group comparison matrix of opportunities
Tablica 6. Vektor te`ine i omjer konzistencije za matricu usporedbe
prilika
Opportunities – Prilike
Strengthening the operation of the machinery rings in the field of
forestry – Ja~anje operacija udru`enja u {umarstvu
Partial professionalization of work – Djelomi~na
profesionalizacija rada
w
0.8000
0.2000
CR=0.0000
Table 7 Priority vector and consistency ratio of group comparison matrix of threats
Tablica 7. Vektor te`ine i omjer konzistencije za matricu usporedbe
prijetnji
Threats – Prijetnje
w
Subsidies for equipment investments – Poticaji za nabavu opreme 0.5168
Fostering the association of Slovenian public forestry service into
other forms of cooperation
0.2470
Poticanje udru`ivanja u druge oblike suradnje koje dolazi od
javnoga {umarskoga servisa Slovenije
Competition among providers/members – Konkurencija me|u
0.2361
dobavlja~ima/~lanovima
CR=0.0191
According to the results of SWOT factors, the
factor with the highest priority is selected and it
represents a group. The strengths were represented
by the factor »Integration of farmers and private
forest owners«, the weaknesses by »Not enough financial means for operation», the opportunities by
»Strengthening the operation of machinery rings in
the field of forestry«, and threats by the factor »Subsidies for equipment investments«.
Furthermore the priority vectors (w) and consistency rations (CR) of group comparison matrices for
SWOT groups are presented in Table 8.
The analysis conducted according to A’WOT
method showed that in order to establish the strate-
Table 8 Priority vector and consistency ratio of group comparison matrix of SWOT groups
Tablica 8. Vektor te`ine i omjer konzistencije za matricu usporedbe
grupa SWOT
SWOT groups – SWOT grupe
Strengths – Snage
Weaknesses – Slabosti
Opportunities – Prilike
Threats – Prijetnje
CR=0.0292
Croat. j. for. eng. 33(2012)1
w
0.0895
0.2836
0.2428
0.3840
[. Pezdev{ek Malovrh et al.
gic objectives, machinery rings have to minimize
weaknesses (w = 0.2836) to avoid threats (w = 0.3840).
A defensive approach to strategic planning was,
therefore, applied to form suitable strategies. Such
defensive formation of strategies represents a combination of the following strategic objectives: acquisition of financial means for the operation of machinery rings not only from the government, but also
from self–promotion of the operation of machinery
rings. This would provide the services offered to
non–members who would pay a certain price in exchange. The promotion itself depends on the time of
the people in charge, and therefore points into the direction of professionalizing the operation of larger
machinery rings. In this way, the collaboration among
members would improve and there would be less
mistrust of the operation and fewer personal interests. If these weaknesses are surmounted, the members will try to influence the tenders for subsidiaries
and take care of the promotion of machinery ring integration. In this case the fostering of integration by
the Slovenian public forestry service into other forms
of cooperation would not represent a threat anymore. Additionally, together with the improved operation of machinery rings, the competition among
the service providers would decrease.
5. Conclusion – Zaklju~ak
According to the results of our study, as well as
previous experiences with A’WOT (e.g. Pykalainen
et al. 1999, Ananda and Herath 2003, Wolfslehner et
al. 2005, [egoti} et al. 2007), we can assent that the
combined use of the AHP method and SWOT analysis is a promising approach in supporting strategic
decision making processes. The evaluation of strategies with A’WOT method forces the decision makers
to analyze the situation more precisely than in the
cases where only the standard SWOT analysis is
used.
Machinery rings are nowadays an essential part
of strategic (operational) management in Slovenian
agriculture and forestry. However, there seem to remain many opportunities that are not fully exploited. In the future, it is necessary to expand the membership of machinery rings to new farmers and forest owners, to promote the services offered by members, to strengthen the operations in the field of forestry and to find new opportunities in the market,
especially in the sense of cooperation between forest
owners and forestry enterprises. All these facts enable members to operate efficiently, while using the
newest technologies and to optimize the production
costs.
111
[. Pezdev{ek Malovrh et al.
The Present State and Prospects of Slovenian Private Forest Owners’ Cooperation ... (105–114)
The optimal use of the available machinery and
the exchange of farmer-to-farmer services should
become tasks and prospects of Slovenian machinery
rings. This endeavor ensures a cost efficient use of
machinery – machinery management. However, machinery rings can offer much more to their members.
Machinery rings can provide economic assistance,
i.e. assistance at peak working season and social
assistance, i.e. social operations in emergencies. Thus,
with the expansion of services to private individuals, as for example winter service suppliers, companies, municipalities and public institutions, the members can gain additional income and labor opportunities.
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Sa`etak
Sada{nje stanje i perspektive suradnje privatnih {umovlasnika Slovenije
u udru`enjima za upotrebu {umske mehanizacije
U Republici Sloveniji prevladavaju privatne {ume. Razvoj i gospodarenje privatnim {umama povezani su s
promjenama dru{tveno-ekonomske strukture privatnoga {umoposjeda, koje se o~ituju u smanjenju veli~ine privatnih posjeda, porastu broja {umovlasnika, niskom intenzitetu gospodarenja, neadekvatnoj opremi i nedovoljnoj
upotrebi {umske mehanizacije.
Za racionalno gospodarenje privatnim {umama i zadovoljavaju}u upotrebu mehanizacije potrebna je suradnja
privatnih {umovlasnika, koja }e smanjiti tro{kove i omogu}iti upotrebu novih, suvremenijih na~ina {umskoga rada
u privatnim {umama.
Stanje i perspektive suradnje u upotrebi {umske mehanizacije u Republici Sloveniji analizirani su anketiranjem
privatnih {umovlasnika i analizom A’WOT (SWOT + AHP analiza). Za anketiranje su ~lanovi udru`enja za upotrebu {umske mehanizacije (dalje udru`enja) podijeljeni u pet razreda prema veli~ini posjeda, a unutar tih razreda
obavljen je sustavni izbor. Uzorak je obuhvatio 172 ~lana udru`enja. Na anketu je odgovorilo 43,8 % ispitanika. Za
identificiranje SWOT ~imbenika intervjuirani su predsjednici udru`enja koja rade u {umarstvu. Predsjednici su
izrazili svoje mi{ljenje o snagama, slabostima, prilikama i prijetnjama njihova djelovanja na gospodarenje privatnim {umama.
Rezultati anketiranja pokazuju da su ~lanovi udru`enja samo djelomi~no zadovoljni s njegovim djelovanjem.
Razlog su tomu nedovoljne aktivnosti i informiranje o mogu}nostima upotrebe kapaciteta ostalih ~lanova, premalo
ponu|enih aktivnosti i suradnje me|u ~lanovima te problemi s obra~unavanjem njihovih usluga. 93,9 % privatnih
{umovlasnika u udru`enju smatra da su njihovi interesi u vezi s gospodarenjem privatnom {umom zadovoljeni
(tablica 2). Za ve}inu ~lanova udru`enja su prikladan oblik suradnje u odnosu na njihove potrebe u gospodarenju
{umom. Suradnja u udru`enju ima budu}nost pogotovo ako se imaju na umu dru{tveno-ekonomske promjene iz
~istih u mje{ovita gospodarstva. Sve manje i manje privatnih {umovlasnika imat }e dovoljno vremena, prakti~noga
iskustva i znanja za gospodarenje {umom. Zbog toga }e u budu}nosti ve}i dio privatnih {umovlasnika tra`iti informacije i unajmljivati usluge udru`enja.
Rezultati analize A’WOT pokazuju da je glavna snaga udru`enja povezivanje poljoprivrednika i privatnih {umovlasnika (tablica 4), a slabost nedovoljna sredstava za provo|enje aktivnosti (tablica 5). Glavna je prilika ja~anje
aktivnosti udru`enja u {umarstvu (tablica 6), a prijetnja su nedovoljni poticaji za nabavu opreme, koji su dostupni
samo velikim {umovlasnicima (tablica 7). Obrambeni pristup strate{koga planiranja primijenjen u obliku prikladne strategije udru`enja pokazuje da je potrebno smanjiti slabosti kako bi se izbjegle prijetnje.
Croat. j. for. eng. 33(2012)1
113
[. Pezdev{ek Malovrh et al.
The Present State and Prospects of Slovenian Private Forest Owners’ Cooperation ... (105–114)
Udru`enja su danas neizostavni dio slovenske poljoprivrede i {umarstva, me|utim njihove se mogu}nosti nedovoljno koriste. U idu}em je razdoblju potrebno pro{iriti ~lanstvo na nove poljoprivrednike i {umovlasnike, promicati usluge ~lanova, ja~ati suradnju u {umarstvu i prona}i nove tr`i{ne mogu}nosti, osobito u suradnji me|u poduze}ima. To }e omogu}iti ~lanovima da rade gospodarski efektivno primjenom najnovije tehnologije i optimiziranjem tro{kova proizvodnje. Slovenska udru`enja danas nude samo usluge koje se odnose na tro{kovno efektivnu
upotrebu strojeva, a mogli bi ponuditi ~lanovima puno vi{e: gospodarsku i socijalnu pomo}.
Klju~ne rije~i: suradnja u upotrebi mehanizacije, udru`enja {umske mehanizacije, privatne {ume, anketiranje,
metoda A’WOT, strate{ko planiranje
Authors’ address – Adresa autorâ:
[pela Pezdev{ek Malovrh, PhD.
e-mail: spela.pezdevsek.malovrh@bf.uni-lj.si
Prof. Lidija Zadnik Stirn, PhD.
e-mail: lidja.zadnik@bf.uni-lj.si, PhD.
Prof. Janez Kr~, PhD.
e-mail: janez.krc@bf.uni-lj.si
Biotechnical Faculty
Department of forestry and renewable forest
resources
Ve~na pot 83
1000 Ljubljana
Received (Primljeno): September 13, 2011
Accepted (Prihva}eno): November 21, 2011
114
SLOVENIA
Petra Gro{elj, Msc.
e-mail: petra.groselj@bf.uni-lj.si
Biotechnical Faculty
Department of wood science
Cesta VIII/34
1000 Ljubljana
SLOVENIA
Croat. j. for. eng. 33(2012)1
Original scientific paper – Izvorni znanstveni rad
Productivity Linear Regression Models of
Tree-Length Harvesting System in Natural
Coastal Aleppo Pine (Pinus halepensis L.)
Forests in the Chalkidiki Area of Greece
Christos Gallis, Gavriil Spyroglou
Abstract – Nacrtak
Time studies of harvesting and skidding tree-length logs in Aleppo pine (Pinus halepensis
L.) natural coastal forests of Chalkidiki area in northern Greece were carried out to formulate
linear regression models and to evaluate productivity. The harvesting system consisted of a
feller with chainsaw for felling, delimbing and crosscutting, and a four wheel drive farm
tractor, with a 74 kW engine, equipped with a special winch attached to the tractor three
point hitch for the extraction of tree length logs. Operational factors such as distance, slope,
volume and the time required for harvesting and extracting tree length logs were measured
and recorded. The results illustrate that the calibrated linear regression models show strong
correlation between the time needed for harvesting operations and the extraction distance
from the stump to the forest road.
Keywords: tree length system; extraction; time studies; linear regression models; productivity;
Aleppo pine; natural coastal forests
1. Introduction – Uvod
The forest biomass industry operates under severe economic pressure for lower production costs.
One way to lower the pressure is the most effective
cost control of raw material (Bushman and Olsen
1988, Gallis 1997, Gallis 2003). Timber cost has been a
topic of continuous concern for forest managers and
forest products industry. Technical and economic
utilization of forest biomass depends on various factors related to terrain conditions, transportation networks and harvesting technologies, as well as systems, silviculture and forest operations management
(Cavalli and Grigolato 2010, Picchio et al. 2011).
Working time studies are very often used for the
analysis of productivity of various forest biomass
harvesting systems (Gallis 2004, Magagnotti et al.
2012, Picchio et al. 2009, Savelli et al. 2010, Spinelli
and Nati 2009). Thus collected data may be used to
formulate regression models for the correlation of
several parameters of the harvesting system with
time and productivity (Cubbage et al. 1988, Gallis
1997, Gallis 2004, Gingras 1988, Katenidis et. al. 1983).
Croat. j. for. eng. 33(2012)1
These models could be used for planning and economical analysis of forest operations (Howard 1988,
Samset 1990, Gallis 2004).
The harvesting and removal of forest biomass
from the natural forests of Greece requires a profitable and environmentally acceptable logging system. This system should be able to thin and remove
individual trees from even aged stands with dense
understory of evergreen broadleaved shrubs or uneven-aged stands, and to harvest mature trees. The
most critical stage of the logging operation is forwarding logs from the forest site to the roadside
landings. It may account up to 30% of the total harvesting cost and can cause some environmental damages (Fisher et al. 1980, Gallis 2003, Picchio et al.
2011, Spinelli et al. 2010).
Currently in Greece, the main system widely employed is felling, delimbing, topping and crosscutting
trees with a chainsaw in the stump area and extracting medium and small-sized logs from the forest site
to roadside landings by special vehicles, farm tractors
and horses. The use of tree length system has been
115
Christos Gallis and Gavriil Spyroglou
Productivity Linear Regression Models of Tree-Length Harvesting... (115–123)
recently introduced in Greek forestry mainly in stands
with terrain of low inclination. Modified farm tractors are currently used for wood extraction. In the
tree length system, trees are usually extracted with a
part of the load dragged along the ground with a
cable winch attached to the rear system of the farm
tractor (winching operation). Farm tractors may have
some advantages such as increased flexibility for
other types of work, and lower capital investment.
The flexibility and relatively low capital input can
reduce the need to maintain high productivity and
annual utilization (Johansson 1997). Further research
of skidding operations time studies for tree length
system operations is required in Greece.
The aim of this study was to calibrate regression
models through working time studies in order to
define the effect of stand and operational factors
such as distance, slope, and volume on time of harvesting and on extracting tree length logs from the
forest site to the forest road. The study was carried
out in the coastal Aleppo pine (Pinus halepensis) natural forests of Sithonia peninsula of Chalkidiki area
in northern Greece.
2. Materials and methods – Materijal
i metode
The working time studies were conducted in several different uneven-aged Pinus halepsinis stands
and they examined the harvesting and extraction
cycles. The harvesting system applied consisted of
selecting individual trees, one by one, through high
thinning positive selection. More specifically, in each
stand, the plus or future trees are identified intuitively on a regular distribution pattern by the forester in charge and, according to the silvicultural
descriptions of the management plan, one or two
trees – competitors are marked for felling (Chatziphilippidis and Konstandinidis, 1995). The marked
trees were felled, delimbed and topped by a chainsaw in the stump area. The extraction was carried
out by a four wheel farm tractor, with a 74 kW
engine, equipped with a special winch attached to
the tractor three point hitch. The stands under study
had no strip roads for extraction. Thus, the operation
was performed with the farm tractor moving on the
forest ground.
The system of harvesting-extraction with farm
tractors consists of a driver and a feller. In several
stands, time studies were performed in order to calculate the time required for the extraction of one tree
length log from the stand to the roadside landing.
The timing method used in this study was the continuous method. According to this method the watch is
in continuous motion and the position of the time
116
indicator is recorded at the beginning of each work
phase or delay and at the end of the total work under
study (Tsoumis and Efthymiou 1973, Barnes 1980,
Niebel 1988, Tsoumis 1992, Gallis 1997, Gallis 2004).
The starting point for timing the extraction cycle
was when the team departed from the roadside to
the stand for loading. An operator performed the
harvesting operations assisted by the driver. The
time was recorded for each cycle element: travelling
empty to the place of loading, felling, delimbing,
waiting to be loaded, using the winch for loading,
travelling with the load, arriving at the landing,
waiting to be unloaded, unloading, and cross cutting. In addition to time measurements, other parameters were also recorded for each cycle such as the
volume of tree length logs, the distance from the
landing to the loading point, and the slope. For every
full cycle of harvesting-extraction operation, the full
cycle and the harvesting time productivity were calculated as cubic meters of tree volume harvested per
hour. 30 complete cycles were recorded (Table 1) in
total. For each numbered log, the volume was calculated using the formula of truncated cone.
Simple linear models (linear regression models) in
the form Y (Time of logging operation) = f (Slope,
Distance, Log volume) were selected. The development
of model equations for each category of logging
operation time was Y = a + b · Sl + c · Dist + d · LogVol,
where Y is the Time needed for logging operations in
minutes, Sl is the terrain slope in (%), Dist is the
distance of the logging site to the forest roadside
landings in meters and LogVol is the volume of the
logs forwarded from the logging site to the forest
roadside landings in cubic meters. The statistical
analysis was performed by using the computer statistical program SPSS 12.0 (Norusis 2003).
3. Results and discussion – Rezultati i
rasprava
The average slope of the study area was 4.6%
denoting a rather flat terrain where a farm tractor
can be easily used for harvesting operations without
a risk of erosion on the skidding roads. The mean
extraction distance was 84.17 m and the mean extracted log volume was 1.95 m3 resulting in a mean
harvesting time of 6 minutes and 9 seconds, which
corresponds to 42.1% of the total time. The mean
extraction time was 3 minutes and 29 seconds, meaning that almost 24% of the total time was spent for
this operation. Travelling empty time was 1':17'' representing 8.7% of the total time of the harvesting
operation. The total time for a complete cycle ranged
from 10 minutes and 27 seconds to 28 minutes and 36
seconds with an average of 14 minutes and 36 seCroat. j. for. eng. 33(2012)1
Productivity Linear Regression Models of Tree-Length Harvesting... (115–123)
Christos Gallis and Gavriil Spyroglou
Table 1 Descriptive statistics of the slope, distance, log volume and times needed for logging operations
Tablica 1. Deskriptivna statistika nagiba terena, udaljenosti, obujma sortimenta i utro{ka vremena pridobivanja drva
Variable
Varijabla
N
N
Min.
Min.
Max.
Maks.
Mean
Arit. sred.
Std. Dev.
St. dev.
30
2
8
4.60
1.45
30
35
207
84,17
50.67
Log Volume – Obujam sortimenta, m
30
6.33
1.95
0.97
Preparation – Priprema za rad, min:sec
28
0.95
0:06
1:24
0:47
0:30
Felling – Ru{enje, min:sec
Slope – Nagib, %
Distance – Udaljenost, m
3
30
0:42
2:36
1:10
0:54
Delimbing – Kresanje grana, min:sec
30
2:09
8:06
4:14
1:40
Skidding – Privla~enje, min:sec
30
1:42
6:03
3:29
1:21
Cross cutting – Trupljenje, min:sec
30
1:42
12:42
4:09
2:15
Travelling empty – Neoptere}ena vo`nja, min:sec
30
0:36
2:30
1:17
0:51
30
10:27
28:36
14:36
3:54
30
3:42
11:48
6:09
2:19
30
4.9
9.9
7.5
1.3
30
10.8
32.2
18.5
4.5
Total time – Ukupno vrijeme, min:sec
Harvesting time – Vrijeme sje~e, min:sec
3
Full cycle productivity – Proizvodnost cijelokupnoga procesa, m /h
3
Harvesting time productivity – Proizvodnost sje~e, m /h
conds. Katenidis (1978) reports that the travelling
empty time consumed one half (50%) of the harvesting time required when mules were used as
animals for extraction and 25% of the total time used
for skidding. The use of machines instead of animals, whenever feasible, reduces considerably the
extraction as well as the travelling empty time. The
harvesting time and the full cycle productivity ranged
between 10.8 to 32.2 and 4.9 to 9.9 m3 per hour with a
mean value of 18.5 and 7.5 m3 per hour, respectively.
Descriptive statistics of the slope, distance, log volume and the necessary times used in logging operations are presented in Table 1.
After the application of linear regression procedure on the above mentioned models, the adjusted
results are shown in Table 2. Model 1 is for the full
cycle operation, Model 2 for travelling empty and
Model 3 for travelling with the load (skidding). For
travelling empty (2) and skidding (3) models, the
only statistically significant independent variable was
the distance, the other two variables, slope and log
Table 2 Linear regression model equations to predict logging time operations
Tablica 2. Linearne regresijske jednad`be modela za predvi|anje utro{ka
vremena pridobivanja drva
Model
Model
Equation
Jednad`ba
1
Tfull = 6.434 + 0.023 · Distance + 3.082 · Log volume
2
Tempty = 0.366 + 0.009 · Distance
3
Tforwarding = 1.909 + 0.012 · Distance
Croat. j. for. eng. 33(2012)1
volume appeared non-significant because for slope,
there is no much variability within the variable
(2–8%) and for the log volume, the 74 kW farm
tractor with its 4100 kg mass used for skidding was
strong enough to carry out the logging without any
delays due to log size and weight. If we suppose that
the tractor was moving by a more or less constant
velocity, when skidding or when travelling empty
from the forest road to the logging site, then the
distance was the only driving variable for the time
needed for the operations.
For model (1), the independent variable slope was
not statistically significant for the reason explained
above, and hence it was removed from the model.
The log volume variable plays an important role accounting for a large proportion of the observed variance (partial adj. R2=0.64). This can be attributed to
the fact that the full cycle time includes harvesting
operations (felling and delimbing) that represent
42.1% of the full cycle operation, making this variable highly significant. Johansson (1997), in his study on small tree harvesting by use of farm tractors
with the crane attached to the front part, when doing
regression analysis of time consumption per work
cycle, found that the tree volume was the only variable that accounted for a large proportion of the
variation in time consumption and that there was no
reason to use a more sophisticated model than that
of the simple regression.
Table 3 shows that all regression models have
large correlation coefficients as well as coefficients of
determination. All the models performed very well,
117
Christos Gallis and Gavriil Spyroglou
Productivity Linear Regression Models of Tree-Length Harvesting... (115–123)
and the variance explained by the models varied
from 74 percent for the full cycle model (1) to 24 percent for the forwarding (3). The Durbin-Watson statistic is between 0.81 and 2.04. For models (1) and (3),
the Durbin-Watson statistic falls within the range 1.5
to 2.5 and the assumption of residuals independence
is satisfied for these models. For model (2) the Durbin-Watson statistic was 0.81 indicating a positive
autocorrelation.
Autocorrelation is the phenomenon that distinguishes time series from other branches of statistical
analysis. For example, if we consider the tractor operator during the travelling empty time. A usual time
cycle varies around one minute and seventeen seconds. The variation may be caused by machine
failure; the dense understorey of evergreen broadleaves characteristic for Allepo pine stands sometimes prevents the operator from keeping a constant
tractor speed, resulting in a run of increased travelling empty time cycle. This is an example of positive
autocorrelation, determined by the Durbin-Watson
statistic for model 2 (0.81), with data falling and
staying below one minute and seventeen seconds for
a few cycles especially when the understorey vegetation is very dense obliging the tractor operator to
reduce a bit the moving speed, then rising above one
minute and seventeen seconds and staying high for
a while, then falling again, and so on.
Table 4 shows the model coefficients and their
significance denoting strong models. The slope variable, represented by the (b) parameter in all models
appeared non significant by the regression analysis
and is not included in the table. The same holds for
the log volume variable, represented by the (b) parameter for models 2 and 3. Multicollinearity is not a
problem for the models because the tolerance statistic was very close to 1, much greater than 0.1, which
is considered the threshold for multicollinearity problems. The variance inflation factor (VIF) was also
around 1 and certainly less than the threshold value
of 5 (Van Laar 1991).
In order to visualize the relationships among the
dependent and independent variables of the calibrated models, three and two dimensional scatter
plots were drawn. Fig. 1 shows the strong positive
linear relationship that exists among the dependent
variable time of various logging operations and the
independent variables, distance and log volume.
The three models were also checked for heteroscedasticity, the third assumption of the linear regression – assumption of constant error variance.
The residual analysis of the models 1 & 3 in Fig. 2
shows that there were no obvious patterns or clustering in the residuals, the residuals were homoscedastic, and the variance remained the same for
every combination of values of the independent va-
Table 3 Statistical summary of the studied models
Tablica 3. Statisti~ki sa`etak ispitivanih modela
Model
Model
R
R2
1
2
3
0.87
0.94
0.49
0.76
0.89
0.24
Adjusted R2
Prilago|eni R2
0.74
0.88
0.21
SE of estimate
Stand. pogre{ka procjene
1.81
0.17
1.07
Durbin-Watson
1.65
0.81
2.04
Table 4 Model coefficient estimates and collinearity diagnosis
Tablica 4. Procjena koeficijenata i dijagnoza kolinearnosti za modele
Model
Model
1
2
3
Tolerance
Tolerancija
VIF
FPV
6.543
Sig.
Razina zna~.
0.000
0.007
3.414
0.002
0.988
1.012
0,348
0.885
0.000
0.988
1.012
a
3.082
0.366
0.061
5.974
0.000
c
0.009
0.001
15.145
0.000
1.00
1.00
a
1.909
0.385
4.955
0.000
c
0.012
0.004
2.956
0.006
1.00
1.00
Parameters
Parametri
Coefficients
Koeficijenti
SE
Stand. pogre{ka
T
T
a
6.434
0.983
c
d
0.023
Sig. – 0.000 means that the coefficient of the model is highly significant; Razina zna~. – 0,000 razumijeva da su koeficijenti modela visoko zna~ajni
VIF – Variance Inflation Factor; FPV – Faktor pove}anja varijance
118
Croat. j. for. eng. 33(2012)1
Productivity Linear Regression Models of Tree-Length Harvesting... (115–123)
Christos Gallis and Gavriil Spyroglou
Fig. 1 Scatter plots between dependent and independent variables of the three models
Slika 1. To~kasti grafikoni zavisnih i nezavisnih varijabli za tri modela
riables. Model 2 shows a slight clustering and as it
can be seen in Table 5, the Kolmogorov-Smirnov and
Shapiro-Wilk tests for the normality of the residuals
appear statistically significant, meaning that either
the relationship in model 2 is not linear or that there
is another variable causing more variability, which
was not considered or measured during data collection. The autocorrelation exhibited by the same
Croat. j. for. eng. 33(2012)1
model might be another source of the clustering in
the residuals.
The assumption of normality was another issue
that had to be tested in order to secure that the
calibrated models are statistically sound. The statistical criteria of Kolmogorov-Smirnov and Shapiro-Wilk shown in Table 5 appear statistically non-significant at a = 0.05 level except Model 2, for which
119
Christos Gallis and Gavriil Spyroglou
Productivity Linear Regression Models of Tree-Length Harvesting... (115–123)
Fig. 2 Residual analysis of the three models
Slika 2. Analiza rezidualnih odstupanja za tri modela
the criteria appeared significant. This deviation from
normality was not a big problem and hence did not
interfere with the regression analysis.
4. Conclusions – Zaklju~ci
From the present study, the following conclusions can be drawn:
120
1. The modified farm tractors can be operated in
tree length harvesting with flexibility and good
productivity in natural stands with low inclination and without strip roads.
2. The calibrated regression models show strong
correlation between the time needed for harvesting operations and the extraction distance
from the stump to the forest road.
Croat. j. for. eng. 33(2012)1
Productivity Linear Regression Models of Tree-Length Harvesting... (115–123)
Christos Gallis and Gavriil Spyroglou
Table 5 Tests of normality of the residuals for the studied models
Tablica 5. Testovi normalnosti rezidualnih odstupanja ispitivanih modela
Model
Model
Statistic
Statistika
1
0.114
df
St. sl.
30
2
0.186
30
0.118
3
Shapiro-Wilk
Kolmogorov-Smirnov
Sig.
Razina zna~.
30
0.200 ns
0.010*
0.200
ns
Statistic
Statistika
0.964
df
St. sl.
30
Sig.
Razina zna~.
0.866
30
0.384 ns
0.001**
0.958
30
0.267 ns
ns
– The respective statistic is non-significant; ns – nema zna~ajne razlike
* – Significant at alpha level (or P-value) = 0.05; * – zna~ajna je razlika za vrijednost p = 0,05
**– Significant at alpha level (or P-value) = 0.001; ** – zna~ajna je razlika za vrijednost p = 0,001
Further studies are needed to define the impact of
site and stand conditions such as steeper slopes,
mixed forests, mountain forests, stands with strip
roads, as well as other related operations such as
delimbing and crosscutting, for more consistent and
sound time study models for tree length harvesting
system covering all types of forests in Greece.
Acknowledgements – Zahvale
This study was financially supported through the
grant for »New Researchers« of the National Agricultural Research Foundation (NAFREF) of Greece
(2002).
5. References – Literatura
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Sa`etak
Linearni regresijski modeli proizvodnosti pridobivanja drva
deblovnom metodom iz prirodnih obalnih {uma alepskoga bora
u predjelu Chalkidiki u Gr~koj
Studij vremena pri sje~i i privla~enju obloga drva uz primjenu deblovne metode u prirodnim obalnim {umama
alepskoga bora (Pinus halepensis L.) u predjelu Chalkidiki u sjevernoj Gr~koj proveden je radi dobivanja linearnih
regresijskih modela i procjene proizvodnosti.
Sustav pridobivanja drva ~inili su sjeka~ s motornom pilom za ru{enje, kresanje grana i prevr{ivanje, dok je za
privla~enje obloga drva kori{ten prilago|eni poljoprivredni traktor koji je imao pogon na sva ~etiri kota~a, snagu
motora 74 kW i posebno vitlo pri~vr{}eno u trima to~kama na stra`njem dijelu vozila. Operativni ~imbenici, na
primjer: udaljenost, nagib terena, obujam oblovine, utro{ak vremena sje~e, izradbe i privla~enja, izmjereni su i
zabilje`eni.
Cilj je ovoga istra`ivanja bio pobolj{avanje regresijskih modela pomo}u studija rada i vremena s namjerom
definiranja utjecaja sastojinskih i operativnih ~imbenika kao {to su: udaljenost privla~enja, nagib terena i obujam
drva na utro{ak vremena sje~e, izradbe i primarnoga transporta iz sje~ine do pomo}noga stovari{ta ({umske ceste).
U istra`ivanom sustavu pridobivanja drva usporedno su radili voza~ traktora i sjeka~. U nekoliko sje~ina proveden
je studij vremena radi izra~una vremena potrebnoga za privla~enje pojedinoga debla iz sje~ine do {umske
prometnice.
Pri snimanju radnoga procesa primijenjena je proto~na metoda kronometrije. Polazi{na to~ka studija vremena
radnoga turnusa privla~enja drva bio je trenutak kada je vozilo krenulo s pomo}noga stovari{ta u sastojinu radi
utovara drva. Jedan je radnik sjekao stabla uz povremenu pomo} voza~a traktora. Vrijeme je bilo zabilje`eno za
122
Croat. j. for. eng. 33(2012)1
Productivity Linear Regression Models of Tree-Length Harvesting... (115–123)
Christos Gallis and Gavriil Spyroglou
svaku sastavnicu radnoga turnusa: vo`nja neoptere}enoga vozila do mjesta utovara, sje~a stabala, kresanje grana,
~ekanje na utovar, skupljanje obloga drva vitlom (privitlavanje), vo`nja optere}enoga vozila, dolazak na pomo}no
stovari{te, ~ekanje na odvezivanje tovara, odvezivanje tovara (istovar) i prikrajanje radi izrade drvnih sortimenata.
Rezultati istra`ivanja pokazuju da su pobolj{ani modeli linearne regresije ~vrsto povezani s vremenom
potrebnim za sje~u i s udaljeno{}u vo`nje iz sje~ine do {umske ceste. Ovo je istra`ivanje pokazalo da se prilago|eni
poljoprivredni traktori mogu koristiti u deblovnoj metodi izradbe drva za primarni transport uz odre|ene
prilagodbe i postizati zadovoljavaju}a proizvodnost u prirodnim sastojinama gdje su manji nagibi terena i koje nisu
sekundarno otvorene (nema {umskih vlaka i traktorskih putova). Tako|er, pobolj{ani regresijski modeli pokazuju
jaku ovisnost utro{ka vremena radova pridobivanja drva o udaljenosti privla~enja iz sje~ine do {umske ceste.
Klju~ne rije~i: deblovna metoda, privla~enje, studij vremena, linearni regresijski modeli, proizvodnost, alepski
bor, prirodne obalne {ume
Authors' address – Adresa autora:
Received (Primljeno): November 25, 2011
Accepted (Prihva}eno): February 8, 2012
Croat. j. for. eng. 33(2012)1
Christos Gallis, PhD
e-mail: cgalis@fri.gr
Gavriil Spyroglou, PhD
e-mail: spyroglou@fri.gr
Forest Research Institute
570 06 Vassilika, Thessaloniki,
GREECE
123
Original scientific paper – Izvorni znanstveni rad
Improving Accuracy in Earthwork Volume
Estimation for Proposed Forest Roads Using
a High-Resolution Digital Elevation Model
Marco Contreras, Pablo Aracena, Woodam Chung
Abstract – Nacrtak
Earthwork usually represents the largest cost component in the construction of low-volume
forest roads. Accurate estimates of earthwork volume are essential to forecast construction
costs and improve the financial control of road construction operations. Traditionally, earthwork volumes are estimated using methods that consider ground data obtained from survey
stations along road grade lines. However, these methods may not provide accurate estimates
when terrain variations between survey stations are ignored. In this study, we developed a
computerized model to accurately estimate earthwork volumes for the proposed forest roads
by using a high-resolution digital elevation model (DEM). We applied our model to three
hypothetical forest road layouts with different ground slopes and terrain ruggedness
conditions. We examined the effects of various cross-section spacings on the accuracy of
earthwork volume estimation assuming that 1-meter spacing provides the »true« earthwork
volume. We also compared our model results with those obtained from the traditional
end-area method. The results indicate that as cross-section spacing increases the accuracy of
earthwork volume estimation decreases due to lack of the ability to capture terrain variations. We quantified earthwork differences, which increased with terrain ruggedness ranging from 2 to 21%. As expected, short cross-section spacing should be applied to improve
accuracy in earthwork volume estimation when roads are planned and located on hilly and
rugged terrain.
Keywords: forest roads, earthwork volume, road design, LiDAR, digital elevation model
1. Introduction – Uvod
Earthwork usually represents the major cost component in the construction of low-volume forest
roads, accounting for over 80 percent of the total
construction cost on steep terrain (Stückelberger et
al. 2006). It is essential to accurately estimate earthwork volumes to improve cost control and budgeting in forest road construction. Traditionally, ground
information for the proposed roads is collected
through a preliminary road centerline survey, where
survey stations are placed usually at every 30 meters
or at major gradient or direction changes to reduce
expensive and labor-intensive field work. Ground
slopes measured at each station is used to calculate
cut and fill areas, which are then used to estimate
earthwork volumes between consecutive cross-sections.
Croat. j. for. eng. 33(2012)1
Earthwork volumes have been conventionally estimated using the average end-area or the prismoidal method (Hickerson 1964). Both methods require
cross-section areas to be of the same type; either cut
or fill. Epps and Corey (1990) developed procedures
to estimate earthwork volumes differently for various configurations (cut and/or fill) of cross-section
areas using the average end-area method. For linear
ground profiles, the prismoidal method is known to
provide more accurate estimates while the average
end-area method generally overestimates earthwork
(Epps and Corey 1990). Easa (1992a) developed a
modified prismoidal method for estimating volumes on non-linear ground profiles. This method is
based on the Pappus's theorem and estimates earthwork volumes approximately as the average of the
volumes resulting from rotating both cross-section
areas about an axis on their respective planes (see
125
M. Contreras et al.
Improving Accuracy in Earthwork Volume Estimation for Proposed Forest Roads ... (125–142)
Hickerson 1964 for more details). The Pappus-based
method provides accurate estimates only when the
two cross-sections are also of the same type (either
cut or fill). Easa (1992b) also developed a mathematical method based on triple integration that can deal
with transition road segments where one of two
consecutive cross-sections has both cut and fill areas,
while the other has only either one. This method is
complicated and applicable only for road segments
where the ground profile is linear (Aruga et al. 2005).
These existing earthwork volume estimating methods assume that the ground slope at each road cross-section is constant, which is unlike for most hilly
and mountainous terrains. Kim and Schonfeld (2001)
developed two methods to estimate cross-section
areas more precisely. These methods use an interpolation method (inverse distance-weighted) to obtain
elevation data, and vector and parametric representation of cross-sections to account for irregular ground
slopes.
The accuracy of all aforementioned methods seems
to improve as the distance between consecutive cross-sections decreases (Kim and Schonfeld 2001). However, cross-sections can only be derived at survey
stations, and an assumption about the homogeneity
of ground slopes between consecutive cross-sections
has to be made. High-resolution DEMs derived from
the light detection and ranging (LiDAR) technology
have recently been incorporated into forest road
planning and design to increase accuracy in volume
estimation by using the elevation data of each raster
grid cell. LiDAR technology is known to provide
accurate estimates of ground surface elevation even
under a dense canopy cover (Reutebuch et al. 2003).
Coulter et al. (2001) applied a 1-meter resolution
LiDAR-derived DEM to estimate earthwork volumes for a proposed forest road. In this method, road
elevation was assigned to each grid cell within the
road template to estimate earthwork volume from
the difference between road and ground surface elevations. However, this simplistic method is only applicable to straight road segments. Aruga et al. (2005)
developed a computer program for forest road design that also uses a 1-meter resolution DEM. Their
model precisely generates cross-sections and calculates areas, and accurately estimates earthwork volumes. As the actual ground profile can be represented more accurately when a shorter distance between cross-sections is applied (Aruga et al. 2005),
earthwork volume estimations using a 1-meter resolution DEM were considered »exact« and comparable with other estimates obtained from different
cross-section spacings and different estimation methods. The study was focused on the optimization of
road design, and, however, limited emphasis was
126
put on numerical procedures and the study does not
provide a thorough analysis of the effects of cross-section spacing on earthwork volume estimation.
Although the accuracy of earthwork volume estimates is expected to increase with decreasing spacing between consecutive cross-sections, to our knowledge, there are no studies evaluating and quantifying the differences in earthwork volume estimates
in various terrain conditions. In this study, we developed a computerized model to accurately estimate
earthwork volumes for the proposed forest roads
using a high-resolution LiDAR-derived DEM. We
examined the effects of cross-section spacings on the
accuracy of earthwork volume estimation by applying the model to the proposed roads in various areas
under different terrain conditions and estimating
earthwork volumes of the roads at different cross-section spacings. Similar to Aruga et al. (2005), we
assumed that 1-meter cross-section spacing provided the »true« earthwork value in our study. Our
computerized model was applied to three hypothetical forest roads laid out on low, moderate, and
steep slope areas, and the earthwork volume estimates from the model were compared with those from
the traditional end-area method, which considers
only the cross-sections located at survey stations.
Lastly, comparisons were also made on road sections
with three levels of terrain ruggedness.
2. Computerized model – Ra~unalni
model
The computerized model developed in this study
was designed to accurately estimate cut and fill volumes for a proposed forest road using a high-resolution DEM. The main input data for the model
include: i) an ASCII text file representing the LiDAR-derived DEM for the area of interest, and ii) a text
file representing the x- and y-coordinates of sequential survey station points along a proposed road.
Based on the cell size (1 meter in our applications)
and the x-and y-coordinates of the lower left corner
of DEM, the model calculates x- and y-coordinates of
each grid cell in the DEM. These coordinates are
used to obtain the ground elevation of each survey
station point along the proposed road gradeline.
2.1 Estimating ground elevation – Procjena
visine terena
Starting from the beginning-of-project (BOP),
ground elevations for each survey station point (SP)
are obtained from the LiDAR-derived DEM. As DEM
elevation values represent the elevation at the center
of the grid cell and since a given SP might not coCroat. j. for. eng. 33(2012)1
Improving Accuracy in Earthwork Volume Estimation for Proposed Forest Roads ... (125–142)
M. Contreras et al.
Fig. 1), and the other three adjacent cells (grid cells
with a square in Fig. 1). The horizontal distances
from the SP to the four grid cells are computed and
their z-coordinates are obtained. The SP z-coordinate is then obtained based on the inverse distance to
each adjacent grid cell and their respective elevation
values (Eq. 1).
Ni
Ni
j =1
j =1
SPZi = å ( dj-1 × z j ) / å dj-1
Fig. 1 Estimating ground elevation on a given point (dot) using the
interpolation method based on four grid cells including the grid cell
containing the point (grid cell with a cross) and three adjacent grid cells
(grid cells with squares)
Slika 1. Procjena visine terena odre|enoga polo`aja (to~ka) primjenom metode interpolacije zasnovane na ~etirima podacima pravilne
mre`e to~aka (polje s kri`i}em) i na trima susjednim poljima (polja s
kvadrati}em)
incide with a grid cell center, an interpolation method is used to estimate the SP z-coordinate. The interpolation method uses inverse distance-weighted
based on its four adjacent grid cells.
For a given SP, (dot in Fig. 1) the model identifies
the grid cell containing it (grid cell with a cross in
"j Î N i
(1)
where, SPZi is the z-coordinate of the ith SP, dj is the
horizontal distance from the jth grid cell to SP, zj is the
z-coordinate of the jth grid cell, and Ni indicates the
set of four closest grid cells to the ith SP. Once the
three-dimensional coordinates of all SP are determined, the model locates a curve for each intersection point and identifies the position of the beginning and end of curve.
2.2 Locating horizontal curves – Odre|ivanje
glavnih to~aka horizontalnoga kru`noga luka
We assumed all SP (n) along a proposed road
except BOP and end-of-project (EOP) become intersection points (PI in Fig. 2), where curves are located
to avoid sharp turns. Each horizontal curve location
is determined based on the x- and y-coordinates of
the SPi, (same as the PI), SPi-1 and SPi+1, and a user
defined minimum allowable radius of the curve (R).
In the United States, R ranges from 18 m to 40 m
Fig. 2 An example of horizontal curve design and nomenclature
Slika 2. Primjer oblikovanja i osnovne sastavnice horizontalnoga kru`noga luka
Croat. j. for. eng. 33(2012)1
127
M. Contreras et al.
Improving Accuracy in Earthwork Volume Estimation for Proposed Forest Roads ... (125–142)
depending on the road standard (Akay 2003). Fig. 2
shows the nomenclature used in the model to determine the location of the beginning and end of the
curve (PC and PT, respectively), and the location of
the curve center (CC in Fig. 2), whose arc passes
through PC, and PT is also determined for posterior
calculations of the curve design.
For each PI, represented by SPi, the model calculates the direction of the two tangent lines in a
two-dimensional (x, y) Cartesian coordinate system
as follows:
m1 =
m2 =
diff _ y 1
diff _ x 1
diff _ y 2
diff _ x 2
=
=
yi - yi-1
xi - xi-1
yi+ 1 - yi
xi+ 1 - xi
(2)
PCX = PIX ±
where, Azim and m are azimuth and direction of a
tangent line, respectively. Then, the central angle (D
in Fig. 2) is calculated as follows:
ì 360- |Azim2 - Azim1 | if |Azim2 - Azim1 |> 180
D=í
(5)
otherwise
î |Azim2 - Azim1 |
Once the angle D is obtained, the model calculates
the tangent distance (T in Fig. 2) from PI to PC and
PT (Eq. 6).
(6)
(m12 × T 2 ) /(1 + m12 )
m1
PTY = PIY ± (m22 × T 2 ) /(1 + m22 )
(3)
if diff _ y ³ 0 Ù diff _ x > 0
if diff _ y > 0 Ù diff _ x £ 0
(4)
if diff _ y £ 0 Ù diff _ x < 0
if diff _ y < 0 Ù diff _ x ³ 0
T = R × tan(D/2)
PCY = PIY ± (m12 × T 2 ) /(1 + m12 )
PTX = PIX ±
where, m1 and m2 represent the direction of the two
tangent lines (one arriving at SPi and one leaving
from SPi), and xi and yi represent the x- and y-coordinates of the ith SP, respectively.
The model converts tangent line directions into
azimuths based on the sign of the numerator and
denominator of the direction (Eq. 4).
ì 90 - tan-1 (m)
ï
-1
ï 270 + tan (m)
Azim = í
-1
ï 270 - tan (m)
ïî 90 + tan-1 (m)
Using m1, m2, and T, the model calculates the two-dimensional coordinates of PC and PT (Eqs. 7–8 and
9–10, respectively) of the curve associated with SPi
by adding or subtracting a difference in the x- and
y-coordinates from the coordinates of the PI (Eqs.
7–10).
(m22 × T 2 ) /(1 + m22 )
m2
(7)
(8)
(9)
(10)
These x- and y-coordinates and the slopes m1 and
m2 are then used to determine the coordinates at the
center of the circle (CC in Fig. 2) as follows:
CCX =
CCX =
PC Y - PTY + (PC X /m1 ) - ( PTX /m2 )
m1-1 - m2-1
PC Y - PTY + (PC X /m1 ) - ( PTX /m2 )
m1-1 - m2-1
(11)
(12)
Once the two-dimensional coordinates of PC, PT,
and CC for each of the n-2 curves have been determined, the model estimates the elevation (z-coordinate) of each of these points as described in the
previous section.
2.3 Calculating road segment distance – Izra~un
staciona`e
The road layout has n station points and thus n-1
straight road segments connecting consecutive station points. As one curved road segment is added for
each of n-2 intersection points, the total number of
road segments (curved and straight segments) becomes 2n-3. Starting from BOP and ending at EOP,
these segments alternate between straight and curved segments.
Fig. 3 Plan view of a proposed road including straight and curved road segments
Slika 3. Polo`ajni nacrt predlo`ene {umske ceste s prikazom ravnih dionica i dionica u kru`nim krivinama
128
Croat. j. for. eng. 33(2012)1
Improving Accuracy in Earthwork Volume Estimation for Proposed Forest Roads ... (125–142)
ì (BOP - PC
) 2 + (BOPY - PC Y (j + 1) ) 2
X
X (j + 1)
ï
ï
SDj = í ( PTX (j - 1) - PC X (j + 1) ) 2 + ( PTY (j - 1) - PC Y (j + 1) ) 2
ï
2
2
ïî ( PTX (j - 1) - EOPX ) + ( PTY (j - 1) - EOPY )
M. Contreras et al.
" j Î Q = {1}
"j Î Q = {3, 5, 7, ... , ( 2n - 5)}
(13)
"j Î Q = {2n - 3}
where, SDj is the horizontal distance of the jth road segment along the road centerline, and PTX(j–1), PTY(j–1), PTX(j+1),
and PTY(j+1) are the x- and y-coordinates of the PT from the (j-1)th segment and the PC from the (j+1)th segment,
respectively (Fig. 3).
For straight segments, the model calculates the
horizontal distance using the x- and y-coordinates of
the previous curve PT and the following curve PC
(Eq. 13). For the case of the first segment, the distance is calculated from BOP until the first curve PC,
and the distance of the last segment is calculated
from the last curve PT to EOP (Eq. 13, Fig. 3).
For the case of curved segments, the model calculates the segment distance as follows:
SDj = 2 × p × R ×
Dj
360
"j Î Q = {2, 4, 6, ... , ( 2n - 4)}
(14)
where, SDj and Dj indicate the horizontal distance
along the road centerline and the deflection of tangents in degrees associated with the jth curved segment, respectively (Fig. 3).
2.4 Locating cross-sections for each road
segment – Odre|ivanje popre~noga presjeka
u svakom profilu ceste
The model determines the number of cross-sections (CSN) for a given road segment based on the
segment distance and a user-defined cross-section
spacing (CSS). CSN for the jth road segment is then
calculated by dividing SDj by CSS (Eq. 15).
CSNj =
SDj
CSS
, as a fractional notation
ì b > 0 Þ CSNj = a + 2
b
CSNj = a if í
c
î b = 0 Þ CSNj = a + 1
(15)
where, CSNj is the number of cross-sections on the jth
road segment, a indicates the integer part of CSNj,
b and c represent the numerator and denominator of
the fractional part, respectively. When the horizontal
distance of a road segment is shorter than CSS (SDj<
CSS, thus a = 0), two cross-sections are located, one at
the beginning and the other at the end of the road
segment.
All cross-sections along a road segment are located perpendicular to the road centerline. For the given jth road segment, the first cross-section is always
located at the beginning of the road segment, the folCroat. j. for. eng. 33(2012)1
lowing cross-sections are spaced successively with
an interval of CSS, and the last cross-section is always
located at the end of the segment.
2.5 Designing cross-sections – Kreiranje
popre~nih presjeka
For the purpose of comparing earthwork volumes estimated using different cross-section spacing,
we simplified the cross-section design and made the
following four assumptions: i) zero-line (balance
point) is always located at half of the road width
(RW), ii) road surface is flat, iii) road does not include
a ditch, and iv) cut and fill slopes are constant. Fig. 4a
presents the cross-section design considered in our
model. For a given cross-section, horizontal distances from the road center (P1 in Fig. 4b) to its edges
(P2 and P3 in Fig. 4b) are assumed to be fixed at
RW/2. However, horizontal distances from P1 to the
points where cut and fill slopes intersect with the
ground profile (P4 and P5 in Fig. 4b) are variable
because they depend on the ground slope.
To obtain the design points necessary to draw a
cross-section, the model first identifies the x-and
y-coordinates of points P2 and P3 using the road
width, the coordinates of P1, and the direction of the
road segment mrs (Fig. 4b). The direction (mrs) is
calculated differently for straight and curved segments (Eq. 16 and 17, respectively).
ì PC Y (j + 1) - P1 Y
"j Î Q = {1, 3, 5, ... , ( 2n - 5)}
ï
ï PC X (j + 1) - P1 X
(16)
mrs = í
ï EOPY - P1 Y
"j Î Q = {2n - 3}
ïî EOP - P1
X
X
-1
æ CC Yj - P1 Y ö
÷ "j Î Q = 2, 4, 6, ... , ( 2n - 4)
mrs = – ç
{
}
ç CC Xj - P1 X ÷
ø
è
(17)
where, CCXj and CCYj represent the x- and y-coordinates of CC associated with the jth curved road
segment. The location of P2 and P3 are then calculated by adding or subtracting a difference in the
x- and y-coordinates from the coordinates of the P1
(Eqs. 18–19).
129
M. Contreras et al.
Improving Accuracy in Earthwork Volume Estimation for Proposed Forest Roads ... (125–142)
Fig. 4 Cross-section design considered by the model (a), and road segment slopes (mrs) used to identify the location of cross-section design points on
straight and curved road segments (b)
Slika 4. Kreiranje popre~nog profila odre|enog modelom (a), te uzdu`ni nagib dionice {umske ceste (mrs) kori{ten za odre|ivanje osnovnih sastavnica
popre~nog profila na ravnim dionicama te u horizontalnim kru`nim krivinama (b)
PY = P1Y ±
( RW / 2) 2
mrs2 + 1
PX = P1X + mrs × (P1Y–PY)
(18)
(19)
where, the two pairs of and represent the locations
of P2 and P3.
To identify the locations of P4 and P5, the model
iteratively places two points (Pt1 and Pt2 in Fig. 5)
along the cross-section at a fixed distance interval,
which is called span-distance (SpD) in our model. At
iteration one, Pt1 starts at the edge of the road (P2 or
P3 for the left or right side of the road, respectively),
and Pt2 starts at meters away from Pt1 (Fig. 5). Thereafter, both points Pt1 and Pt2 are moved farther away
from the road edge by SpD meters at each successive
iteration. At a given iteration, the model calculates
the x-, y-, and z-coordinates of Pt1 and Pt2 using the
horizontal distances of Pt1 and Pt2 from P1. The
model then checks whether the line formed between
Pt1 and Pt2 intersects with the fill or cut slope line.
The iteration process stops when the two lines intersect. Once this intersection point is known, the model calculates the horizontal distances (X_dist) from
the road edge to P4 and P5 (Fig. 5). The model then
calculates the two-dimensional coordinates of points
P4 and P5 using Equations 18 and 19 replacing
(RW/2) with (RW/2 + X_dist).
130
2.6 Calculating cut and fill areas – Izra~un
povr{ine iskopa i nasipa
To obtain ground elevations along a road cross-section, the model establishes ground points along
the cross-section with an interval of SpD meters (Fig.
6a), and then estimates ground elevation on each
point using the DEM and the interpolation method
described in Section 2.1. The model then calculates
cross-section areas (cut and fill) using a well-known
Fig. 5 Iterative process performed by the model to identify the
intersection point (P5) between the cut slope and ground surface
Slika 5. Postupak ponavljanja rada modela pri identificiranju to~ke
sjeci{ta (P5) pokosa iskopa i terena
Croat. j. for. eng. 33(2012)1
Improving Accuracy in Earthwork Volume Estimation for Proposed Forest Roads ... (125–142)
æ CSS × TCA R
ç
ç TCA + TFA
R
R
CVk = è
2
æ
CSS × TCA R
ç CSS ç
TCA R + TFA R
FVk = è
2
æ CSS × TCA L
ö
÷ × TCA R ç
÷
ç TCA + TFA
L
L
ø
+è
2
ö
÷ × TCA L
÷
ø
æ
ö
CSS × TCA L
÷ × TFA R ç CSS ç
÷
TCA L + TFA L
ø
+è
2
ö
÷ × TFA L
÷
ø
M. Contreras et al.
(21)
(22)
where, CVk and FVk are the cut and fill volumes of the kth road section defined by two consecutive cross-sections.
formula (Eq. 20), which provides the area of a polygon based on the coordinates of its vertices. This
formula is derived from one half of the absolute
value of the determinant of the matrix formed by the
two-dimensional coordinates of the polygon vertices
(Hush 1963).
TPN
A = 0.5 × å [( xx p × z p + 1 ) - ( xx p + 1 × z p ) ]
(20)
p =1
where, xxp is the horizontal distance from P1 to the
pth point in the cross-section, zp is the elevation of the
pth point, and TPN is the total number of points
representing one side of the road from P1 where the
area is calculated. Equation 20 provides cut or fill
areas depending on whether all ground elevation
points are above or below the road surface. When both
cut and fill areas are on one side of the road in the
cross-section, where some ground elevation points
are above the road surface and other points are below
the road surface (Fig. 6b), the polygons representing
either cut or fill are identified and their areas are
calculated separately. Areas of the same type (cut or
fill) are then added together to compute the total cut
and fill areas for the right and left side of the road
(TCAR, TFAR, TCAL, and TFAL respectively).
2.7 Estimating cut and fill volumes – Procjena
obujma zemljanih radova
Based on our assumption that road centerlines
are located at the ground level, earthwork volumes
Fig. 6 Cross-section design points used to calculate cut and fill areas (a), and an example of a cross-section having both fill and cut areas on one side of
the road center line (P1) (b)
Slika 6. Osnovne to~ke popre~noga profila kori{tene za izra~un povr{ina iskopa i nasipa (a) te primjer kada se s iste strane popre~noga profila nalaze
povr{ine iskopa i nasipa (P1) (b)
Croat. j. for. eng. 33(2012)1
131
M. Contreras et al.
Improving Accuracy in Earthwork Volume Estimation for Proposed Forest Roads ... (125–142)
Fig. 7 Cross sections taken from straight and curved road segments for earthwork volume estimation
Slika 7. Popre~ni presjeci na ravnim dionicama te u horizontalnim kru`nim lukovima ceste kao podloga za procjenu volumena zemljanih radova
were estimated separately for each side of the road.
For straight road segments we used the modified
average end-area method developed by Epps and
Corey (1990) to estimate earthwork volumes using
the cut and fill areas of consecutive cross-sections
(Eqs. 21–22)
The CSS is the same on both sides of the road
center line for straight road segments, whereas this
is not the case for curved road segments (Fig. 7). For
curved road segments, the model computes the actual cross-section spacing for each side of the road
center line (CSSR and CSSL) separately by calculating
the arc length of a curve whose radius makes the
areas on both sides of the curve equal (A1R= A2R and
A1L= A2L in Fig. 7). The arc lengths can be calculated
as follows:
2
D=
2
R + (R ± RW /2) æ CSS × 360
× çç
2
R
è
"j Î Q = {2, 4, 5, ... , ( 2n - 4)}
2
ö
÷
÷
ø
CSN - 1
k
(24)
k
(25)
å CV
k =1
FVj =
CSN - 1
å FV
k =1
Lastly, the total earthwork of the entire forest
road is calculated by adding the total cut and fill
volumes estimated for each road segment (Eqs. 26
and 27).
TCV =
2 n-3
j
(26)
j
(27)
å CV
j =1
TFV =
2 n-3
å FV
j =1
where, TCV and TFV represent the total cut and fill
volumes of the entire road, respectively.
3. Model applications – Primjena modela
(23)
where, the two values of D represent CSSR and CSSL.
Once cross-section spacings along a curved road
segment are obtained for both sides of the road center line, Equations 21 and 22 are used to estimate cut
and fill volumes between consecutive cross-sections
for curved road segments after CSS in the equation is
replaced with CSSR and CSSL. Then, the total cut and
fill volumes are calculated for the jth road segment
using the following equations:
132
CVj =
3.1 Verification – Provjera
We created a hypothetical forest road to verify the
results of our model and analyze the effects of using
a high resolution DEM on earthwork volume estimates. We compared these estimates with those from
the traditional method, which considers ground information only from pre-defined station points. The
hypothetical road has three station points (Fig. 8a),
resulting in two straight and one curved road segments (Fig. 8b). The hypothetical road was laid out
Croat. j. for. eng. 33(2012)1
Improving Accuracy in Earthwork Volume Estimation for Proposed Forest Roads ... (125–142)
M. Contreras et al.
Fig. 8 Hypothetical forest road layout; a) station point locations, and b) road segment locations
Slika 8. Polo`ajni nacrt hipotetske {umske ceste; a) polo`aj to~aka terenske izmjere, b) polo`aj dionica {umske ceste
in the southern portion of the Mica Creek watershed
located about 67 km southeast of Coeur d’Alene,
Idaho, United States, where a LiDAR-derived, 1-meter
resolution DEM is available. The road was manually
digitized »on-screen« in ArcMap 9.2 based on a
2-meter contour lines layer derived from the DEM of
the area. The ground slope in the area was moderate,
ranging between 30 and 60%. We considered the
following cross-section design and spacing parameters; cut slope (CS) = 1:1, fill slope (FS) = 1.5:1, road
width (RW) = 4 m, radius of curve (R) = 20 m, and
SpD = 1 m.
3.2 Test case studies – Testiranje studije slu~aja
To analyze the effects of various cross-section
spacing on the accuracy of earthwork volume estiCroat. j. for. eng. 33(2012)1
mation, we created the layout of three hypothetical
1 km forest roads. These roads were located in areas
with slopes between 0–30%, 30–60%, and 60–90% in
the southern portion of the Mica Creek watershed to
also examine the effects of ground steepness on earthwork volume estimation. We arbitrarily referred to
these three areas with increasing slope as low, moderate, and steep terrain areas. The roads were manually
digitized »on-screen« in ArcMap 9.2 based on 2-meter contour lines derived from the 1-meter resolution
DEM of the area. The allowable road grade used the
range from -15% to 15%. We assumed that 1-meter
spacing provided the most accurate estimate, and
used the earthwork volume obtained from 1-meter
cross-section spacing as the true volume in comparison with other spacing. Fig. 9 illustrates the layout
133
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Improving Accuracy in Earthwork Volume Estimation for Proposed Forest Roads ... (125–142)
Fig. 9 Layout of the three hypothetical 1 km forest roads located in low (a), moderate (b), and steep (c) slope areas
Slika 9. Prikaz tri hipotetske {umske ceste projektirane na razli~itim kategorijama nagiba terena (a – 0 do 30 %, b – 30 do 60 % i c – 60 do 90 %)
of the low, moderate and steep slope forest roads,
which have 37, 36, and 37 station points, respectively.
We also investigated the effect of terrain ruggedness on earthwork volume estimations. Most of the
existing terrain ruggedness indexes calculated from
ground elevation and aspect are designed to mea-
sure terrain heterogeneity for large areas using typically a 30 meter raster resolution (Riley et al. 1999,
Sappington et al. 2007). When using a high-resolution
1-meter DEM, these indexes are not able to meaningfully capture terrain ruggedness for characterizing
terrain variability along road segments. Therefore,
we computed the coefficient of variation of the fill
Fig. 10 Number and location of cross-sections along a given straight road segment for different cross-section spacings (1, 2, 4, 8, and 16 meters)
Slika 10. Broj i polo`aj popre~nih profila uzdu` ravne dionice {umske ceste za razli~ite ina~ice razmaka izme|u popre~nih profila (1, 2, 4, 8 i 16
metara)
134
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Improving Accuracy in Earthwork Volume Estimation for Proposed Forest Roads ... (125–142)
M. Contreras et al.
Fig. 11 Cross-section diagrams obtained for the 3-SP hypothetical forest road
Slika 11. Crtani popre~ni profil u to~kama terenske izmjere na hipotetskim {umskim cestama
and cut areas from all cross-sections in a given road
segment, and used this coefficient of variation as a
measure of terrain ruggedness in our study (e.g., the
higher coefficient represents the more rugged terrain.) The coefficient was computed for all road segments included in the three hypothetical forest roads.
Then, the road segments were grouped in three ranges of coefficient of variation: low (<20%), medium
(20–40%), and high (³40%).
The same parameter values used in the model verification regarding road design (RW and R), cross-section design (FS and CS), and spacing (SpD) were
used for these applications. To make comparisons
valid, specific cross-section spacings (e.g., 1, 2, 4, 8, 16
meters) were selected so that the same cross-sections
can be used for smaller spacings analyzed (Fig. 10).
Croat. j. for. eng. 33(2012)1
4. Results and Discussion – Rezultati i
rasprava
4.1 Model verification – Provjera modela
Using the values of road design parameters specified above, we calculated cut and fill areas of each
four cross-sections along the hypothetical forest road
layout formed by two straight and one curve segment
(see Fig. 8). Cut and fill areas for these cross-sections
were also calculated manually to verify our model
results (Fig. 11). Table 1 shows the coordinates of all
cross-section design points as well as other points
along the ground profile for each cross-section shown
in Fig. 11. The results of area calculations from the
model perfectly matched those calculated manually.
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Improving Accuracy in Earthwork Volume Estimation for Proposed Forest Roads ... (125–142)
Table 1 X- and Z-coordinates calculated by the model to draw the cross-sections shown in Fig. 11
Tablica 1. Modelom izra~unate koordinate X i Z nacrtane na popre~nim profilima prikazanim na slici 11
BOP coordinates
Koordinata po~etka ceste
X1
Z2
–3.6234
1219.8796
–3.0000
1220.1448
–2.0000
1220.9619
–2.0000
1220.3194
–1.0000
1220.6205
0.0000
1220.9619
1.0000
1221.3924
2.0000
1220.9619
2.0000
1221.8531
3.0000
1222.1539
3.3107
1222.2726
PC2 coordinates
Koordinata po~etka kru`noga luka 2
X1
Z2
–4.3041
1219.1348
–4.0000
1219.2062
–3.0000
1219.5960
–2.0000
1220.6709
–2.0000
1219.8930
–1.0000
1220.3587
0.0000
1220.6709
1.0000
1221.1097
2.0000
1220.6709
2.0000
1221.7045
3.0000
1222.3679
4.0000
1222.8951
4.3946
1223.0655
PT2 coordinates
Koordinata zavr{etka kru`noga luka 2
X1
Z2
–3.3858
1220.2944
–3.0000
1220.3676
–2.0000
1221.2183
–2.0000
1220.6660
–1.0000
1220.9959
0.0000
1221.2183
1.0000
1221.4677
2.0000
1221.2183
2.0000
1221.7801
2.7864
1222.0046
EOP coordinates
Koordinata zavr{etka ceste
X1
Z2
–4.3221
1219.0900
–4.0000
1219.1963
–3.0000
1219.6519
–2.0000
1220.6380
–2.0000
1220.0318
–1.0000
1220.3419
0.0000
1220.6380
1.0000
1221.0162
2.0000
1220.6380
2.0000
1221.4700
3.0000
1221.7593
3.1738
1221.8119
1
X-coordinate represents the horizontal distance in meters from P1 located at the origin of x-axis – koordinata X predstavlja horizontalnu udaljenost u metrima od sredi{nje osi ceste (apscisa slike 11)
Z-coordinate represents elevation in meters – koordinata Z predstavlja nadmorsku visinu u metrima
2
Table 2 Comparisons of cut and fill volumes estimated by the traditional method and the model
Tablica 2. Usporedba procijenjenoga obujma zemljanih radova standardnom metodom i modelom
Distance
Udaljenost
Road gradient
Nagib ceste
m
%
1
21.84
2
25.16
3
26.72
Totals – Ukupno
73.72
–1.33
2.18
–2.17
–
Segment Nº
Br. segmenta
1
Traditional method – Stand. metoda
Cut Volume
Obujam iskopa
Fill Volume
Obujam nasipa
Model – Model
Cut Volume
Obujam iskopa
Fill Volume
Obujam nasipa
Difference – Razlika
Cut Volume
Obujam iskopa
m3
41.1984
38.7107
27.1596
107.0687
29.3726
31.2789
29.3404
89.9919
Fill Volume
Obujam nasipa
%1
31.0145
21.9750
28.8780
81.8676
28.4278
25.0955
35.0607
88.5840
32.84
76.16
–5.95
30.78
3.32
24.64
–16.32
1.59
[(Traditional method – Model) / Model] * 100
Cut and fill volumes were estimated by our model using cross-sections placed every 1 meter. For the
traditional method, we only considered the cross-sections located at the beginning and end of each
road segment. Volume estimates varied widely between both methods (our model and the traditional
method) for the three road segments, ranging from
–6% to 76%, but the circular road segment presented
the largest differences (Table 2). Cut and fill volumes
were overestimated by the traditional method for
road segments 1 and 2 (from 3 to 76%), and underestimated for the last road segment (from 6 to 16%).
All in all, the traditional method overestimated the
total cut and fill volumes for the 3-segment hypothetical forest road by 30% and 2%, respectively,
when compared with the results of the model.
136
Considerable variability in the cut and fill areas
along the three road segments indicated that ground
slopes along the road vary significantly (Fig. 12).
This terrain variability caused the large differences in
earthwork volume estimates between the two methods. While our model (by using 1-meter cross-section spacing) is able to capture details in terrain variations, these terrain details are ignored when only
few cross-sections are considered in the traditional
method. We also calculated the average value of the
end areas resulted from the model and compared it
with that from the traditional method (Fig. 12). The
differences between the model average and the traditional method have a similar relationship as shown
in the earthwork volume estimates presented in Table
2. This also suggests that the differences in earthCroat. j. for. eng. 33(2012)1
Improving Accuracy in Earthwork Volume Estimation for Proposed Forest Roads ... (125–142)
M. Contreras et al.
Fig. 12 Cut and fill areas for the 3-SP hypothetical forest road calculated by the model and the traditional method
Slika 12. Povr{ine iskopa i nasipa u to~kama terenske izmjere na hipotetskim {umskim cestama izra~unate modelom i standardnom metodom terenske
izmjere
Croat. j. for. eng. 33(2012)1
137
M. Contreras et al.
Improving Accuracy in Earthwork Volume Estimation for Proposed Forest Roads ... (125–142)
Fig. 13 Cut and fill volumes estimated by the model for the three hypothetical 1 km forest roads at different cross-section spacings
Slika 13. Modelna procjena obujma iskopa i nasipa za tri hipotetske {umske ceste duljine po 1 km i za razli~ite razmake izme|u mjerenih popre~nih
profila
138
Croat. j. for. eng. 33(2012)1
Improving Accuracy in Earthwork Volume Estimation for Proposed Forest Roads ... (125–142)
work volumes between the two methods are caused
by their different level of abilities to capture terrain
variations. Due to the limitation in obtaining the
»true« earthwork volume for a given road segment,
it is impossible to properly verify our model for its
earthwork volume estimation. However, our comparisons between the model results and the manual
calculations of cut and fill area confirm that our
model calculates correctly the earthwork volume and
provides accurate estimates based on the assumption that the high resolution LiDAR-derived DEM
provides an accurate representation of the ground
surface.
4.2 Test case studies – Testiranje studija slu~aja
The model results of earthwork estimation for
different cross-section spacings on the three hypothetical 1000-meter roads are presented and compared with the traditional method in Figure 13. A
trend line was added to the estimated earthwork
volumes from our model to show the pattern of
changes in volume across different cross-section
spacings. For the low slope hypothetical road, the
traditional method (labeled as »Tra« in Fig. 13) overestimated both cut and fill volumes by 5.0% and
5.9%, respectively, compared with the results of the
model with 1-meter cross-section spacing. For the
moderate slope road, the traditional method underestimated cut volume by 1.7% but overestimated fill
volume by 1.9%. In contrast, the traditional method
overestimated cut volume by 2.2% but underestimated fill volume by 12.3% for the road located on
steep terrain. The model results from different spacings show a general pattern indicating that as cross-section spacing increases, the earthwork volume
estimates become closer to the volumes estimated by
the traditional method. This is likely explained by
the fact that, as cross-section spacing increases, the
ability to capture terrain variations that may exist
between consecutive cross-sections decreases, making the volume estimates become closer to those of
the traditional method. Although the trend lines may
suggest a relationship between the results of our
model and the traditional method, no evidence of
consistency in over- or underestimation of earthwork volumes was found. Cut and fill volumes were
either overestimated or underestimated depending
on the specific terrain conditions of road segments.
Although Aruga et al. (2005) did not consider the
same factors we did in this study, both studies realized that distance between cross-stations is important
for accurately estimating earthwork volume. The
shorter the distance, the larger ability we have in
describing ground variability along the road lay out.
Thus, it may be possible to estimate earthwork voluCroat. j. for. eng. 33(2012)1
M. Contreras et al.
me more accurately with short distances between
cross-sections.
The results of earthwork estimation for the three
ranges of terrain ruggedness are presented in Fig. 14.
The number of road segments included in each terrain ruggedness class (coefficient of variation) is different. Therefore, to compare the three terrain ruggedness classes, we plotted the average cut and fill
volume per linear meter of road for each cross-section spacing used by the model and the traditional
method. As expected, the model results of cut and
fill volume estimation were similar to the results of
the traditional method on the road segments that
have a low coefficient of variation. For road segments that are in the medium class of coefficient of
variation, the difference in cut volume estimates between the model and the traditional method was
minor, but fill volumes estimated by the traditional
method were 13% lower than the model results with
1-meter cross section spacing. Lastly, for the road
segments with high coefficient of variation (highly
rugged terrain), the traditional method overestimated cut volumes by 10.4%, while it underestimated
fill volumes by 20.9%. In general, it is noticed that
the differences in earthwork volume estimates between our model and the traditional method become
larger as terrain ruggedness increases.
Previous studies conducted by Aruga et al. (2005)
and Akay (2003) also highlighted the importance of
short distances between cross-sections in improving
the accuracy of earthwork volume calculation, which
is consistent with our findings in this study. The
more rugged is the terrain where a forest road is laid
out, the more important it would be to set out cross-sections in short distances in order to obtain an accurate estimation of earthwork volume. We recognize,
however, that surveying a large number of cross-sections in the field might be a time-consuming
task. We hope that the use of our model coupled with
a high-resolution DEM can help improve the accuracy in earthwork volume estimation without much
additional field work.
5. Conclusions – Zaklju~ci
In this study, we developed a computerized model
to accurately estimate earthwork volumes of low-volume forest roads using a high-resolution DEM,
and analyzed the effects of cross-section spacing on
the accuracy of earthwork volume estimates. Although the accuracy of earthwork is expected to
increase as cross-section spacing is reduced, to our
knowledge, our model is the first attempt to quantify the differences between methods using ground
information only at station points (the average meth-
139
M. Contreras et al.
Improving Accuracy in Earthwork Volume Estimation for Proposed Forest Roads ... (125–142)
Fig. 14 Cut and fill volumes estimated by the model for the road segments classified into three terrain ruggedness classes across different cross-section spacings
Slika 14. Modelna procjena obujma iskopa i nasipa dionica {umske ceste razdijeljenih u tri kategorije neujedna~enosti terena za razli~ite razmake izme|u
mjerenih (procijenjenih) popre~nih profila
140
Croat. j. for. eng. 33(2012)1
Improving Accuracy in Earthwork Volume Estimation for Proposed Forest Roads ... (125–142)
od) and using high resolution DEM. When ignored,
large terrain variations along road segments, as evidenced by the calculations of cut and fill areas from
cross-sections spaced every 1meter, resulted in significant earthwork estimation errors. Our model offers
a tool to help forest engineers to rapidly assess alternative forest road layouts and assist with planning
activities to ensure the economic efficiency of forest
road construction.
The model verification and application results
correspond with previous studies (Kim and Schonfeld 2001, Aruga et al. 2005) in terms of the relationship between accuracy and cross-section spacing.
Assuming that 1-meter cross-section spacing provides the »true« earthwork volumes, the accuracy of
earthwork volume estimates decreases with the increase of cross-section spacing. Moreover, the discrepancies in earthwork volume estimates between our
model and the traditional end-area method become
larger in more rugged terrain. Consequently, short
cross-section spacing should be used to capture terrain variations and estimate earthwork volume more
accurately when forest roads are planned and located on mountainous and rugged terrain.
Several assumptions regarding cross-section design were made to simplify the estimation of areas
and volumes as described in the method section.
Although such assumptions may not seem practical,
they do not affect our purpose of comparing earthwork volumes estimated at different cross-section
spacings. In addition, the model can be further improved to consider real-world forest road survey
and design practices.
6. References – Literatura
Akay, A., 2003: Minimizing total cost of construction, maintenance, and transportation costs with computer-aided
forest road design. PhD dissertation in Forest Engineering.
Oregon State University. 229p.
Aruga, K., Sessions, J., Akay, A. E., 2005: Application of an
airborne laser scanner to forest road design with accurate
earthwork volumes. Journal of Forest Research 10: 113–123.
M. Contreras et al.
Coulter, E. D., Chung, W., Akay, A. E., Sessions, J., 2001:
Forest road earthwork calculations for linear road segments
using a high resolution digital terrain model generated
from LiDAR data. In: Proceedings of the first precision
forestry symposium. University of Washington, College of
Forest Resources. Seattle, Washington, USA. June 17–20,
2001, 125–129.
Easa, S. M., 1992a: Modified prismoidal method for nonlinear ground profiles. Surveying and Land Information
Systems 52(1): 13–19.
Easa, S. M., 1992b: Estimating earthwork volumes of curved
roadways: Mathematical model. Journal of Transportation
Engineering 118: 834–849.
Epps, J. W., Corey, M. W., 1990: Cut and fill calculations by
modified average-end-area-method. Journal of Transportation Engineering 116(5): 683–689.
Hickerson, T. F., 1964: Route location and design. New
York, McGraw-Hill, 5th edition
Hush, B., 1963: Forest mensuration and statistics. Ronald
Press Co, New York. 474p.
Kim, E., Schonfeld, P., 2001: Estimating highway earthwork cross sections by using vector and parametric representation. Transportation Research Record 1772: 48–54. Paper No 01-2682
Reutebuch, S. E., McGaughey, R. J., Andersen, H., Carson,
W. W., 2003: Accuracy of a high-resolution digital terrain
modelunder a conifer forest canopy. Canadian Journal of
Remote Sensing 29(5): 527–535.
Riley, S. J., DeGloria, S. D., Elliot, R., 1999: A terrain ruggedness index that quantifies topographic heterogeneity.
International Journal of Science 5: 1–4.
Sappington, J. M., Longshore, K. M., Thompson, D. B.,
2007: Quantifying landscape ruggedness for animal habitat analysis: A case study using bighorn sheep in the
Mojave desert. The Journal of Wildlife Management 71(5):
1419–1426.
Stückelberger, J., Heinimann, H., Burlet, E., 2006: Modeling spatial variability in the life-cycle costs of low-volume
forest roads. European Journal of Forest Research 125(4):
377–390.
Sa`etak
Pobolj{anje to~nosti procjene zemljanih radova za predlo`ene {umske ceste primjenom
digitalnoga modela terena visoke rezolucije
Zemljani su radovi (radovi na donjem ustroju) najve}i tro{ak pri izgradnji {umskih cesta maloga prometnoga
optere}enja i ~ine oko 80 posto ukupnih tro{kova izgradnje. To~nost procjene obujma zemljanih radova prijeko je
potrebna pri procjeni tro{kova izgradnje {umskih cesta, racionalizaciji i kontroli tro{kovne sastavnice te pri
Croat. j. for. eng. 33(2012)1
141
M. Contreras et al.
Improving Accuracy in Earthwork Volume Estimation for Proposed Forest Roads ... (125–142)
izgradnji i uspostavi ekonomski u~inkovite primarne {umske prometne infrastrukture. Koli~ina se zemljanih
radova kod {umskih cesta uobi~ajeno temelji na procjeni podataka dobivenih terenskom izmjerom na trasi {umske
ceste. Povr{ina popre~nih profila procjenjuje se u svakoj to~ki izmjere, a zatim se klasi~ne metode, kao {to su metoda
prosje~nih povr{ina ili metoda prizme, primjenjuju za izra~un obujma zemljanih radova izme|u susjednih
popre~nih profila. Navedene metode pretpostavljaju jednoli~an teren izme|u popre~nih profila, {to pri kona~noj
procjeni rezultira nedovoljno to~nim podacima u brdskim i planinskim podru~jima.
U ovom je istra`ivanju razvijen ra~unalni model pobolj{ane to~nosti procjene zemljanih radova na {umskim
cestama primjenom visoko razlu~iva digitalnoga modela terena. Istra`ivan je utjecaj udaljenosti izme|u profila na
to~nost procjene obujma zemljanih radova primjenom predlo`enoga ra~unalnoga modela. Istra`ivane se {umske
ceste nalaze u razli~itim reljefnim podru~jima, a prikazane su specifi~nim terenskim ~imbenicima te procjenom
koli~ine zemljanih radova za razli~ite razmake izme|u profila. Analiziran je utjecaj razmaka izme|u popre~nih
profila na to~nost procjene koli~ine zemljanih radova. Nadalje, utvr|ena je varijabilnost povr{ina popre~nih profila
koja je kori{tena kao mjera nejednolikosti terena te su istra`eni i u~inci spomenute varijabilnosti na to~nost
procjene obujma zemljanih radova.
Izra|eni je ra~unalni model primijenjen na trima hipotetskim {umskim cestama na terenima nagiba <30 %,
30–60 % i 60–90 %, a procjena obujma zemljanih radova dobivenih modelom uspore|ena je sa standardnom
metodom povr{ina u to~kama terenske izmjere. Op}enito gledaju}i, rezultati pokazuju kako pove}anje razmaka
izme|u popre~nih profila smanjuje to~nost procjene obujma zemljanih radova zbog nemogu}nosti uzimanja u obzir
nejednolikosti terena. Utvr|ene su razlike u procjeni obujma zemljanih radova izme|u predlo`enoga modela i
klasi~nih metoda u rasponu od 2 do 12 % neovisno o nagibu terena. Jasniji je smjer primije}en kada se uspore|uju
procjene obujma zemljanih radova predstavljenim ra~unalnim modelom u odnosu na standardne metode. Pove}anje nejednolikosti terena proporcionalno utje~e na razliku uspore|enih metoda u rasponu od 2 % na jednolikim
terenima (izra`eno niskim koeficijentom varijacije povr{ine profila) pa do 21 % na nejednolikim terenima (izra`eno
visokim koeficijentom varijacije povr{ine profila).
Klju~ne rije~i: {umske ceste, obujam zemljanih radova, projektiranje cesta, LiDAR, digitalni model terena
Authors’ address – Adresa autorâ:
Asst. Prof. Marco A. Contreras, PhD.
e-mail: marco.contreras@uky.edu
University of Kentucky
College of Agriculture
Department of Forestry
KY40546-0073 Lexington
Thomas Poe Cooper Building 214
USA
Received (Primljeno): September 15, 2011
Accepted (Prihva}eno): February 21, 2012
142
Pablo Aracena, Graduate Research Assistant
e-mail: pablo.aracena@umontana.edu
Assoc. Prof. Woodam Chung, PhD.
e-mail: woodam.chung@umontana.edu
University of Montana
College of Forestry and Conservation
Department of Forest Management
MT59812 Missoula
USA
Croat. j. for. eng. 33(2012)1
Original scientific paper – Izvorni znanstveni rad
Planning Forest Accessibility with a Low
Ecological Impact
Eugen Iordache, Mihai-Daniel Nita
zh , Ioan Clinciu
Abstract – Nacrtak
This paper examines a new approach to forest accessibility planning based on a GIS road development algorithm and some topographically derived indices. The aim of the paper is to
propose and validate a method of assessing forest accessibility introducing an ecological approach, based on morphological impact. For the case study, both cartographic material (DEM)
and measured items (existing road network) were used in applying the method. The case
study offered the data and possibility to analyze, compare and take into consideration the
ecological impact on planning forest accessibility.
Keywords: planning, forest accessibility, ecological impact, soil erosion, GIS
1. Introduction – Uvod
Romanian forest lands extend over 6.3 million ha,
representing 27% of the total area of the country. The
distribution of forest lands is such that 90% of it is on
terrain classified as hills or mountains. Hence, it
follows that the majority of forestry works are carried
out on rough topography, where the slopes frequently account for more than 25% of the whole area.
Forest accessibility is low due to the lack of adequate access roads. From a total of 6.3 million ha of
forest land, only 4.1 million ha could be considered
accessible; the rest of these forest lands are not connected to an existing transport system. The road density of the forest road network is 6.2 m/ha (Iordache
2007). At present, the available forest transport system (truck roads, narrow gauge railways, public
roads, servicing roads) consists of 39,186 km intended to cover various forest activities.
Forestry production always covers considerable
areas and from the point of view of natural forest
management simple road construction is not sufficient. According to Dietz et al. (1984) and Dürrstein
(1998) a proper forest opening has always to be developed in a sequence of stages:
Þ connecting the forest to the public transport system (roads, railroads),
Þ access to the different parts of the forest,
Þ access to the single compartments or units of the
forest.
Croat. j. for. eng. 33(2012)1
Due to low road density in Romania, planning of
forest accessibility remains a main issue in further
development of the road network. Taking into consideration ecological principles, like soil erosion, terrain disruption, GIS based algorithms can offer a
sustainable ecological planning of forest accessibility (Iordache and Nita 2008).
The main ecological impact made by road development can occur by landsliding from road surfaces
during plantation harvest and post-harvest periods.
It is estimated that 50–90% of sediment in planted
forests comes from roads (Fransen et al. 2001). Sediments from roads can have a bigger environmental
impact than landslide sediments because of the higher concentrations of fine sediments (Elliot et al. 1993,
Fahey and Marden 2000, Hicks and Harmsworth
1989). Sediment may affect water habitats and landscape ecology by affecting the natural flow of the
rivers and perturbing geomorphic channel processes
by excessive sedimentation.
Quantifying possible morphological impact from
forest roads represents an important issue both for
road planners and for decision makers. This can either
be done by implementing potentially expensive erosion control measures after the road network has been
established or by designing the forest road network in
a way to minimize erosion (Cochrane et al. 2007).
This is why the aim of the present study is to propose and validate a method of road network deve-
143
Eugen Iordache et al.
Planning Forest Accessibility with a Low Ecological Impact (143–148)
lopment that takes into consideration areas with high
occurrence of ecological perturbation. The purpose
of research is to allow forest road planners to minimize the impact of forest roads on morphometry and
consequently on habitats and ecology.
2. Material and Methods – Materijal
i metode
The research material included an existing road
network divided into 11 road segments situated in
Lesuntu Mare Upper Watershed (Fig. 1). This watershed is situated in a mountainous area of Carpathian
Mountains.
The following research materials were used:
Þ Cartographic data – DEM extracted from topographic contour lines, having a 5 m cell size (pixel)
and 1 m height accuracy (according to topographic plan specifications),
Þ Measured data – 11 road segments measured in
the field with a handheld GPS (3 m accuracy).
The method itself contains the following calculating steps:
Þ Preparatory– correcting the DEM by removing
sinks and peaks,
Þ Accessibility calculation – calculating the accessibility distance from every cell to road network.
Accessibility was calculated using cost function
GIS based algorithm developed in ArcMap 9.2. From
the cell perspective, the objective of the cost functions is to determine the least costly path to reach the
Fig. 1 Location of the studied forest road network
Slika 1. Polo`aj istra`ivane mre`e {umskih cesta
cell from the least costly source for each cell location
in the analysis window. For each cell, determination
was made of the least accumulative cost path from a
source, the source that allows for the least cost path,
and the least cost path itself.
The formula used by algorithm to calculate the
total cost from one cell to another is:
Cost_dist =
Surface_dist × Vertical_factor × (Friction × Horizontal_factor)
2
(1)
Fig. 2 Determination of horizontal factors
Slika 2. Odre|ivanje horizontalnih faktora
144
Croat. j. for. eng. 33(2012)1
Planning Forest Accessibility with a Low Ecological Impact (143–148)
Eugen Iordache et al.
harsh ecological conditions. From this point of
view, TRI supports an easy way for determining
the areas where a forest road construction can
lead to higher ecological impact than in normal
conditions.
Þ Mapping the zones with the highest ecological
risk – The proposed method uses both the cost
distance grid and topographic grids for better
quantifying the areas where the forest accessibility provides the lowest ecological impact.
Þ Tracing the areas for the best placement of the
new roads.
3. Results and discussion – Rezultati
i rasprava
Fig. 3 Horizontal factor dependence function
Slika 3. Funkcija ovisnosti horizontalnoga faktora
The horizontal factors determine the difficulty of
moving from one cell to another while accounting for
the horizontal elements that may affect the movement. To determine the HF for moving from one cell
to the next, the prevailing horizontal direction at the
processing cell was established from the horizontal
direction raster (Fig. 2). A linear function was used as
horizontal factor function, (Fig. 3), in order to set the
algorithm to stop any distance calculation over the
ridges.
Data analysis involves four steps:
Þ Inaccessible area identification – based on accessibility raster, a threshold was used in order to
identify areas situated more than 500 m away
from the network.
Þ Morpho–Ecological impact assessment – calculating ruggedness index and determining the possible ecological influence of the new road. The
topographic ruggedness index (TRI) was developed by Riley et al. (1999) and is used to express
the amount of elevation difference between adjacent cells of a digital elevation model. The calculus uses the difference in elevation values of a
central cell and the neighboring cells. TRI is then
derived and corresponds to average elevation
change between any point on a grid and the surrounding area. Habitats and many factors influencing them (micro-climate, humidity, soil layer,
etc.) directly correspond to morphometry (slope,
aspect, curvature). Higher slopes influence shallow soil layers, lower humidity and therefore
Croat. j. for. eng. 33(2012)1
The digital elevation model was used for calculating Lesuntu Mare Upper Watershed forest accessibility (Fig. 4).
By setting the distance threshold to up to 1 km to
the nearest road, the resulting grid was divided in
2 areas: accessible and inaccessible forested areas
(Fig. 5).
This first step in the proposed methodology offers a useful geographic distribution of the inacces-
Fig. 4 Aspect used as data input for calculating the forest accessibility
Slika 4. Ekspozicija kori{tena kao ulazni podatak za izra~un pristupa~nosti {umi
145
Eugen Iordache et al.
Planning Forest Accessibility with a Low Ecological Impact (143–148)
Fig. 5 Accessible and inaccessible forested zones
Slika 5. Pristupa~na i nepristupa~na {umom obrasla podru~ja
cessible: 113B, 127C, 126E, 123C, 123D, 118B, 118D,
118C, 126D, 120A, 119B, 124B, 123B, 125A, 126B,
126F, 127B – in total 262 hectares.
Using traditional road planning methods, a possible route was created in order to increase accessibility in these compartments.
Using the ruggedness index (Riley et al. 1999),
the erosion risk zones were derived in order to identify the zones where higher ecological impact of the
roads could be expected (Fig. 6). Knowing these
areas, some road sections were marked as highly
prone to erosion.
In practice two recommendations appeared to fit
in this issue:
Þ either change the course in order to detour the
zones with high ecological impact,
Þ either apply an additional cost to those sections
in order to compensate the ecological impact if no
other solution is possible.
The application of the method is simple and requires few input data. The computational time depends directly on the area of digital elevation model,
which affects the application of the simulation.
Using the above method by adding accessibility
to 262 hectares, the results revealed possible additional costs in 4 road segments. This simulation
offered additional information not only about the
costs that can occur, but also about the specific
zones characterized with a high probability of erosion processes.
4. Conclusions – Zaklju~ci
Fig. 6 Mapping the zones with the highest erosion risk
Slika 6. Kartiranje podru~ja s najve}im rizikom od erozije
sible forested areas, which is a key goal for forest
road planners and forest managers.
For example taking a compact area and using GIS
tools the next compartments were found as inac-
146
From the very beginning, planning and building
forest roads have severely impacted the ecosystem.
The idea of identifying the areas with low ecological
impact is not a new one but it cannot be identified in
the methods of forest road planning. The complexity
of the phenomenon is a special problem.
With the above method, the purpose of this paper
was to underline that using a GIS application and
geospatially referenced data, the path with the lowest ecological impact on the soil and indirectly on the
ecosystem can be easily identified.
Depending on the accuracy of the data input, the
output can either result in a large scale planning
(based on SRTM model or other global models), or in
a small scale planning and management (based on
the model developed with LIDAR techniques or topographical measurements). The output data not
only offered the estimation of the potential risk to the
zone, but additionally also offered geographic information on the method outcome.
Croat. j. for. eng. 33(2012)1
Planning Forest Accessibility with a Low Ecological Impact (143–148)
The proven fact that planning forest accessibility based on low ecological impact can be done based
on real and accurate data will be a strong and sustainable argument to support this approach in practice.
Acknowledgements – Zahvala
This paper is supported by the Sectorial Operational Programme Human Resources Development
(SOP HRD), financed by the European Social Fund
and by the Romanian Government under the Contract No. POSDRU/6/1.5/S/6.
We would like to thank the scientific reviewers
for suggestions and recommendations made in order to increase the quality of this paper.
5. References – Literatura
Cochrane, T. A., Egli, M., Phillips, C., Acharya, G., 2007:
Development of a forest road erosion calculation GIS tool
for forest road planning and design. International Congress on Modelling and Simulation: Land, Water & Environmental Management: Integrating Systems for Sustainability, Christchurch, New Zealand, December 1–5 2007,
1273–1279.
Dietz, P., Knigge, W., Löffler, H., 1984: Walderschließung.
Verlag Paul Parey, Hamburg und Berlin, 1–426.
Dürrstein, H., 1998: Opening up of a mountainous region –
decision-making by integration of the parties concerned
applying cost-efficiency analysis. In: Proceedings of the
Seminar on environmentally sound forest roads and wood
Eugen Iordache et al.
transport, June 17–22, 1996, Sinnaia, Romania, FAO Rome,
34–43.
Elliot, W. J., Foltz, R. B., Luce, C. H., 1993: Validation of the
WEPP model for forest roads. In: ASAE International Winter Meeting, December 14–17, 1993, Chicago, IL. ASAE.
Fahey, B.D., Marden, M. 2000: Sediment yields from a
forested and a pasture catchment, coastal Hawke’s Bay,
North Island, New Zealand. Journal of Hydrology (NZ)
39(1): 49–63.
Fransen, P. J. B., Phillips, C. J., Fahey, B. D., 2001: Forest
road erosion in New Zealand: overview. Earth Surface
Processes and Landforms 26(2): 165–174.
Hicks, D. M., Harmsworth, G. R., 1989: Changes in Sediment Yield Regime During Logging at Glenbervie Forest,
Northland, New Zealand. In: Proceedings of the 1989 Hydrology and Water Resources Symposium, Christchurch,
NZ, 424–428.
Iordache, E., 2007: Opening up the Romanian forests: Presents and perspectives. In: Proceedings of Austro 2007 –
FORMEC’07 »Meeting the Needs of Tomorrows’ Forests:
New Developments in Forest Engineering«, October 7–11,
2007, Wien–Heiligenkreuzl, Austria, University of Natural
Resources and Applied Life Sciences Viena, CD-ROM.
Iordache, E., Nita M., 2008: Using GIS applications in road
network development taking into consideration soil erosion.
In: Proceedings of 3rd International Scientific Conference
»Fortechenvi 2008«, May 26–30, 2008, Prague, Chech Republic, Mendel University of Agriculture and Forestry Brno.
Riley, S. J., De Gloria, S. D., Elliot, R., 1999: A terrain
ruggedness that quantifies topographic heterogeneity. Intermountain Journal of Science 5(1–4): 23–27.
http://webhelp.esri.com (accesed 1st march 2011).
Sa`etak
Planiranje otvaranja {uma na osnovi okoli{ne pogodnosti
U ovom se radu istra`uje mogu}nost planiranja otvaranja {uma primjenom GIS-a temeljem mre`e {umskih
cesta te nekih topografskih izvedenih indeksa. Cilj je rada predlo`iti i potvrditi metodu procjene pristupa~nosti
{ume uvo|enjem ekolo{koga pristupa s obzirom na morfolo{ki utjecaj. Za potrebe studije te primijenjene metode
kori{teni su kartografski podaci (DEM – digitalni model terena) i izmjereni prostorni podaci (postoje}a cestovna
mre`a). Studija je ponudila analizu ekolo{koga utjecaja na planiranje pristupa~nosti {uma.
Podru~je istra`ivanja uklju~ilo je mre`u postoje}ih {umskih cesta podijeljenu u 11 cestovnih segmenata
smje{tenih na lokaliteta Lesuntu Mare u Karpatima.
U istra`ivanju su kori{teni:
Þ kartografski podaci – digitalni visinski model dobiven iz topografskih slojnica, veli~ine }elije 5 m × 5 m i
visinske to~nosti unutar jednoga metra
Þ izmjereni podaci – 11 cestovnih odsje~aka (segmenata) izmjerenih na terenu s ru~nim GPS-om (polo`ajne
to~nosti 3 metra).
Sama metoda sadr`i ove korake prora~una:
Þ pripremni – ispravljanje (korigiranje) digitalnoga visinskoga modela uklanjanjem vrhova i dolova (najve}ih i najmanjih vrijednosti)
Croat. j. for. eng. 33(2012)1
147
Eugen Iordache et al.
Planning Forest Accessibility with a Low Ecological Impact (143–148)
Þ prora~un pristupa~nosti – prora~un pristupne udaljenosti od svake }elije do cestovne mre`e kori{tenjem
tzv. tro{kovne funkcije (iz grupe funkcija Spatial Analyst ra~unalnoga programa »ESRI Arc GIS 9.2«)
Þ procjena morfolo{ko-ekolo{koga utjecaja – prora~un indeksa neujedna~enosti terena i odre|ivanje mogu}ega
ekolo{koga utjecaja nove ceste na okoli{
Þ kartiranje podru~ja s najve}im ekolo{kim (erozijskim) rizikom
Þ odre|ivanje podru~ja za najbolji prostorni smje{taj novoplaniranih cesta.
Za prora~un pristupa~nosti {umi Lesuntu Mare izra|en je digitalni model terena (slika 1). Kao funkcija
horizontalnoga faktora kori{tena je linearna funkcija (slika 3) kako bi se odredio algoritam koji zaustavlja svaki
daljnji prora~un udaljenosti ako se nai|e na greben (sedlo). Postavljanjem praga udaljenosti do jednoga kilometra
od najbli`e {umske ceste rezultantni je raster razdijeljen u dva podru~ja: pristupa~nu i nepristupa~nu {umsku
povr{inu. Kori{tenjem tradicionalnih metoda planiranja cesta kreirane su mogu}e trase kako bi se pove}ala
otvorenost pojedinih {umskih povr{ina (odjela). Koriste}i indeks neujedna~enosti terena (Riley i dr. 1999) izlu~ene
su zone rizika od erozije kako bi se identificirala podru~ja u kojima bi okoli{ni utjecaj cesta bio ve}i, a gradnja
nepovoljna.
Upotrebom metode dodatnoga tro{ka na pojedinim odsje~cima zbog kompenzacije ekolo{koga utjecaja pove}ana
je otvorenost na dodatna 262 hektara, a rezultati su ukazali na mogu}e dodatne tro{kove na 4 cestovna odsje~ka.
Ova je simulacija ponudila dodatne podatke ne samo o tro{kovima koji se mogu pojaviti ve} i o podru~jima koja su
izlo`ena visokoj vjerojatnosti pojave erozije. Istra`ivanje je pokazalo va`nost primjene GIS-a pri analizi geoprostorno referenciranih podataka kojima se jednostavno mo`e identificirati trasa na kojoj je najmanji ekolo{ki utjecaj na
tlo ili posredno na ekosustav. Ovisno o to~nosti te preciznosti unesenih podataka, izlazni se podaci mogu koristiti ili
za planiranje velikih razmjera ili za planiranje i upravljanje podru~jima lokalnoga karaktera.
Klju~ne rije~i: planiranje, otvaranje {uma, utjecaj na okoli{, erozija tla, GIS
Authors' address – Adresa autorâ:
Received (Primljeno): March 9, 2011
Accepted (Prihva}eno): August 11, 2011
148
Asst. Prof. Eugen Iordache, PhD.
e-mail: i.eugen@unitbv.ro
zh , MSc.
Mihai-Daniel Nita
e-mail: nita_mihai_daniel@yahoo.com
Prof. Ioan Clinciu, PhD.
e-mail: torenti@unitbv.ro
Faculty of Silviculture and Forest Engineering
Transilvania University of Brasov
Sirul Bethoven 1
500123 BraÕov
ROMANIA
Croat. j. for. eng. 33(2012)1
Original scientific paper – Izvorni znanstveni rad
Static Horizontal Positions Determined
with a Consumer-Grade GNSS Receiver:
One Assessment of the Number of Fixes
Necessary
Pete Bettinger, Krista Merry
Abstract – Nacrtak
Over the course of a year, a consumer-grade GNSS receiver was used to collect data in three
forest types in northeastern Georgia (USA). During each visit, fifty position fixes were collected to estimate a horizontal position. Since there has been a significant amount of debate
regarding the appropriate number of position fixes to collect to determine a position, this
analysis was conducted to understand whether the static horizontal position error (a)
changed over the collection period of fifty position fixes, (b) was significantly different than a
single position fix collected to estimate the positions, and (c) was a function of forest type.
We failed to reject the hypothesis that static horizontal position accuracy does not significantly change with increasing numbers of position fixes collected to determine a position,
yet we favor rejecting the hypothesis that trends do not differ by forest type or by density of
trees per unit area. The results are not entirely conclusive, and the time (season) of year may
influence the results observed within certain forest types (e.g., young coniferous forests). We
observed a trend that the static horizontal position accuracy in a young coniferous forest, on
average, improved from a position determined by a single position fix to a position determined from the average of fifty position fixes. A much less relevant trend in accuracy was observed in a deciduous forest, and no trend at all was observed in an older coniferous forest.
Keywords: Global navigation satellite systems, static horizontal position accuracy, root mean
squared error, linear regression
1. Introduction – Uvod
Satellite navigation and positioning systems (or
more commonly, Global navigation satellite systems
(GNSS)) utilize electromagnetic energy emitted by
earth-orbiting devices (space vehicles, or satellites)
to establish positions on earth. The United States
(NAVSTAR GPS), the Russian Federation (GLONASS),
the European Union (GALILEO), India (IRNSS), and
China (COMPASS or BiDou-2) all either have developed, or are developing, GNSS that will provide
signals useful in determining positions on earth. Each
of these programs broadcasts, or plans to broadcast,
signals in various ranges near the L1 (about 1575
MHz) and L2 (about 1228 MHz) band frequencies of
the electromagnetic spectrum. GNSS receiver manufacturers are developing (or have developed) techCroat. j. for. eng. 33(2012)1
nology to collect and use the information emitted by
the satellites to determine positions on earth, and to
facilitate mapping or navigational processes. In practice and in the published literature, GNSS receivers
are generally divided into three classes: survey-grade,
mapping-grade, and consumer-grade (or recreation-grade). Survey-grade receivers can provide sub-centimeter static horizontal position accuracy in open
conditions, and sub-meter accuracy in or near forests
(Pirti 2008), yet lengthy signal acquisition times may
be required. Mapping-grade receivers may be able to
provide sub-meter static horizontal position accuracy in open conditions, but usually 2 – 5 m accuracy
in forests. Consumer-grade receivers are the lowest
cost of the three classes, and generally provide static
horizontal position accuracy in the 5 to 15 m range in
forested conditions.
149
P. Bettinger and K. Merry
Static Horizontal Positions Determined with a Consumer-Grade GNSS Receiver ... (149–157)
Augmentation processes are available to increase
the quality of data collected by GNSS receivers. These
include space-based augmentation systems (e.g., the
United States WAAS program, the European Space
Agency EGNOS program, the Canadian MSAT program, and others), ground-based augmentation systems (differential GPS or DGPS, and real-time kinematic or RTK processes), and post-process differential correction. Depending on the receiver used and the
data the receiver provides, some or all of these augmentation processes may be available. In some cases,
particularly with low-cost consumer-grade GNSS receivers, very few augmentation processes may be
available. Using GNSS technology in a forested environment presents perhaps one of the most challenging data collection situations, because of the effects of trees on signals (Pirti 2005). The influence of
tree canopies on satellite signals is important, as horizontal and vertical accuracy and precision (even
with survey-grade receivers) can be affected (Pirti
2008). Even though contemporary GNSS receivers
may have advanced satellite tracking technologies,
signals are noisier, weaker, and subject to multipath
and diffraction when forced to pass through tree canopies (Pirti 2008). Therefore, in forestry, the accuracy of positions determined with GNSS technology is of concern, since manufacturer’s statements
of typical data quality do not include a description of
the testing environment.
GNSS technology is now widely used in forestry
and other natural resource fields, and professionals
frequently use data collected with these devices for
positional and navigational purposes. Some examples
of uses include the delineation and identification of
forest cutting area boundaries, forest roads, forest
trails, inventory plot locations, streams, and wildlife
nest locations. The need and desire for highly accurate locational information is understandable since
many management decisions are based on data such
as these. A number of recent research efforts have
evaluated and illustrated the usefulness of GNSS
technology in natural resource management (e.g.,
Andersen et al. 2009, Danskin et al. 2009a, 2009b,
Keskín et al. 2009, Wing 2009, Bettinger and Fei 2010,
Klimánek 2010, Pirti et al. 2010, Ransom et al. 2010).
These and other studies conducted within the last
decade provide forest managers with periodic assessments of the positional accuracy of GNSS technology under forested conditions. However, the number of determined horizontal position fixes necessary to obtain the highest level of static horizontal
position accuracy possible under tree canopies is
still open to debate. About a decade ago, Sigrist et al.
(1999) suggested that numerous (300) static horizontal position fixes were necessary at each point visited, yet others (e.g., Bolstad et al. 2005, Wing and
Karsky 2006) have since suggested that the static
horizontal position determined from an average of a
large set of position fixes may be no better than the
position determined from a single position fix. Other
research (Wing et al. 2008, Danskin et al. 2009a) has
suggested a small set (30 or fewer) of static horizontal
position fixes are preferred. Most of these discussions
concern consumer-grade or mapping-grade GNSS
receivers, since it is well known that survey-grade
GNSS receivers need a significant amount position
fixes to arrive at very precise and highly accurate
positions (Hasegawa and Yoshimura 2003, Yoshimura and Hasegawa 2003, Naesset and Gjevestad
2008, Andersen et al. 2009).
The objectives of this work were therefore to understand how static horizontal position accuracy might
change with the number of position fixes collected
during a visit to a known control point.
The hypotheses are:
H1: Static horizontal positional accuracy does not
significantly change with an increasing number of position fixes used to determine a position’s location.
H2: Trends in static horizontal positional accuracy,
with an increasing number of position fixes, do not
differ based on forest type or tree density.
Using data collected over the course of one year
(and previously described in Bettinger and Fei 2010),
we address these two hypotheses.
2. Materials and Methods – Materijal
i metode
Between September 2008 and September 2009,
data were collected with a Garmin Oregon 300 consumer-grade GPS receiver nearly every day, under a
variety of environmental conditions. Static horizontal positions were determined in a young coniferous
forest (loblolly pine, Pinus taeda), an older coniferous
forest, and a deciduous forest, each located within
the Whitehall Forest GPS Test Site1 in Athens, GA.
The purpose of this study was to determine whether
long-term data collected with a consumer-grade GPS
receiver were sensitive to stand type, time of year,
and a number of environmental variables. In a previously published study (Bettinger and Fei 2010), we
found no significant relationship between observed
1
http://warnell.forestry.uga.edu/Warnell/Bettinger/GPS/UGA_GPS.htm
150
Croat. j. for. eng. 33(2012)1
Static Horizontal Positions Determined with a Consumer-Grade GNSS Receiver ... (149–157)
P. Bettinger and K. Merry
(older hardwood) forest. The deciduous forest is dominated by oak (Quercus spp.) and hickory (Carya
spp.). All three control points are located in what we
considered upper slope positions for the surrounding area, and therefore represented the best choices
for comparison among the three forest types. The
three control points were visited once per test day
over the course of a year, the order of visit to each
point was randomized, and fifty position fixes were
collected at each point during each visit. The travel
time between each of the three required about three
minutes. Our assumption (collecting fifty position
fixes at each point during each visit) is consistent
with recent studies (Danskin et al. 2009a, 2009b, Wing
2008, Wing et al. 2008), yet is a compromise based on
previous research in this area. Although until now
Fig. 1 A map of the three Whitehall Forest GPS Test Site points used in
this research
Slika 1. Karta pozicijâ pokusa GPS-om u {umi Whitehall koje su se
koristile u ovom istra`ivanju
static horizontal positional accuracy and several environmental variables (air temperature, relative humidity, atmospheric pressure, and solar wind speed).
No significant differences were noted within a forest
type as seasons of the year changed. The average
static horizontal position accuracy was 11.9 m, 6.6 m,
and 7.9 m for the young coniferous, older coniferous,
and deciduous forests, respectively (Bettinger and
Fei 2010).
Three control points (numbers 6, 31, and 37) from
those available at the Whitehall Forest GPS Test Site
were selected for this research (Fig. 1). Control point
37 is located in the young loblolly pine forest (Fig. 2),
and the forest conditions at the time of the study are
illustrated in Table 1.
Control point 31 is located in the older coniferous
forest, and control point 6 is located in the deciduous
Fig. 2 An aerial view of the Whitehall Forest GPS Test Site and the three
test points used in this research
Slika 2. Zra~ni snimak GPS-om pokusnih pozicija u {umi Whitehall i triju
testnih pozicija kori{tenih u ovom istra`ivanju
Table 1 Characteristics of the forests on the Whitehall Forest GPS Test Site (Georgia, USA) where the study was conducted
Tablica 1. Zna~ajke {uma na podru~ju Whitehall (Georgia, SAD) ispitivanom GPS-om gdje je provedena studija
Characteristic – Zna~ajka
Forest age – Dob {ume
Basal area – Temeljnica
Tree density – Broj stabala
Aspect – Polo`aj, inklinacija
Slope – Nagib
Elevation – Nadmorska visina
Canopy closure – Obrast
Croat. j. for. eng. 33(2012)1
Forest type – Tip {ume
Young coniferous – Mlada {uma ~etinja~a Older coniferous – Starija {uma ~etinja~a
15 years
60 – 70 years
2 –1
30 m ha
20 m2ha–1
182 ha–1
146 ha–1
Southwest – Jugozapadna
South – Ju`na
8%
2%
212 m
222 m
95%
50%
Deciduous – [uma lista~a
60 – 70 years
20 m2ha–1
356 ha–1
Northeast – Sjeveroisto~na
18%
210 m
90%
151
P. Bettinger and K. Merry
Static Horizontal Positions Determined with a Consumer-Grade GNSS Receiver ... (149–157)
the results have not been statistically tested, at the
time of data collection we observed a number of
patterns in the fifty position fixes collected. These
included: (1) static horizontal position accuracy increased as the number of position fixes increased, (2)
static horizontal position accuracy decreased as the
number of position fixes increased, and (3) static
horizontal position accuracy increased, then decreased, or vice versa as the number of position fixes
increased. There seemed to be no clear reason for
these patterns, and the patterns were not consistent
within a forest type on a data collection day.
This research was unfunded, therefore the lead
author decided that approximately 20 minutes per
day could be spared to collect data at the test site. In
addition, it was assumed that only one GNSS receiver
would be assessed, and that the operating parameters of the receiver would be fixed for the entire
duration of the study so that similar data collection
conditions would be used. This implied that during
each visit to each control point, the consumer-grade
receiver was plumbed directly over the control point.
The lead author would then stand on the north side
of each control point as data was collected. Space-based augmentation of signals would be disabled
since the receiver was unable to report the percentage of time the service was available. Finally, position fixes were captured manually, using a 2 – 3
second interval.
Static horizontal position data were collected between 10:30 AM and 16:30 PM, and varied according
to the daily schedule of the lead researcher. We found
it impossible to collect data during a consistent period of time throughout a year, given other responsibilities. That being said, the average Coordinated
Universal Time (UTC) for data collection activities in
the older coniferous forest was 19:45 in the fall season, 19:40 in the winter season, 18:11 in the spring
season, and 17:04 in the summer season (as reported
in Bettinger and Fei 2010). The effect of variations on
data collection activities on the results is unknown,
however trends in data collection times (e.g., consistently collecting data in the morning in the winter
season) were not evident.
The raw (non-transformed) data representing the
root mean squared error (RMSE) of each position fix
determined was used in a linear regression analysis
to determine the slope and coefficient of determination (R2) of a line that best fits the fifty position fixes
of a visit to a control site. This analysis was performed for all 298 days of the study, and each of the three
forest types visited during these days. The slope of
the regression line should be negative if additional
position fixes increase the static horizontal position
accuracy, should be positive if additional position
152
fixes decrease the static horizontal position accuracy,
and will be nearly zero if additional position fixes
have no effect on static horizontal position accuracy.
In these cases of simple linear regression, the independent variable is the RMSE of each position fix,
and the dependent variable is the position fix number (1 to 50). For presentation purposes, we average
the slope values and the coefficient of determination
values to help determine whether to accept or reject
the first hypothesis, that static horizontal positional
accuracy would not be significantly different with an
increasing number of position fixes used to determine
a position’s location. An analysis of these results by
season is also performed. For the purpose of this
study, the fall season covered the period from September 15, 2008 to December 14, 2008, the winter season covered the period from December 15, 2008 to
March 14, 2009, the spring season covered the period
from March 15, 2009 to June 14, 2009, and the summer season covered the period from June 15, 2009 to
September 15, 2009.
Given a full set of fifty position fixes collected
during a single visit to a single control point, this
data was reduced to six estimates of RMSE: (1) the
first position fix, (2) the average of the first ten position fixes, (3) the average of the first twenty position
fixes, (4) the average of the first thirty position fixes,
(5) the average of the first forty position fixes, (6) the
average of all fifty position fixes collected. To be
clear, RMSE was determined for each position fix,
and the RMSE values were then averaged to arrive at
the group average static horizontal error. Since there
was a significant amount of variation in RMSE values from one day to the next, the difference between
the RMSE of the first position fix and the average
RMSE values of the other five groups were used in
the analysis. This analysis was designed to address
the second hypothesis, which suggested that the results may differ based on forest type or tree density.
This analysis was also performed by season to determine whether seasonal variation may explain some
of the differences in the data collected.
3. Results – Rezultati
The average change in static horizontal position
accuracy for positions determined in each of the
three forest types, from the first position fix determined to the last (the fiftieth), was negligible, as
evidenced by the mean and median slope of regression lines fitted to the sequence of position fixes captured during each visit to a control point (Table 2).
This implies that the first hypothesis cannot be
rejected, however other results should also be considered. For example, in Table 2 one can see that the
Croat. j. for. eng. 33(2012)1
Static Horizontal Positions Determined with a Consumer-Grade GNSS Receiver ... (149–157)
P. Bettinger and K. Merry
Table 2 Average regression-related information from 50 position fixes collected per visit to three forest types on the Whitehall Forest GPS Test Site
(Georgia, USA)
Tablica 2. Prosje~ni regresijski podaci za 50 polo`ajnih ~vrstih to~aka prikupljenih po snimanju u razli~itim tipovima {uma na istra`ivanom podru~ju –
Whitehall (Georgia, SAD)
Mean
Srednja vrijednost
Slope, b1 – Nagib, b1
Coefficient of Determination R2
Vrijednost koeficijenta odre|ivanja, R2
Slope, b1 – Nagib, b1
Coefficient of Determination, R2
Vrijednost koeficijenta odre|ivanja, R2
Slope, b1 – Nagib, b1
Coefficient of Determination, R2
Vrijednost koeficijenta odre|ivanja, R2
–0.020
0.595
–0.003
Median
Medijana
Minimum
Minimalna
Maximum
Maksimalna
vrijednost
vrijednost
Young coniferous – Mlada {uma ~etinja~a
–0.011
–0.588
0.700
0.000
Older coniferous – Starija {uma ~etinja~a
–0.006
–0.300
Percent of days within one standard
deviation of the mean
Postotak dana unutar standardne
devijacije srednje vrijednosti
0.297
92
0.893
79
0.332
92
0.546
0.640
0.000
0.938
72
0.003
Deciduous – [uma lista~a
–0.008
–0.250
0.562
91
0.548
0.674
0.917
69
minimum and maximum slope values for regression
lines developed on individual visits can be either
positive (indicating a reduction in accuracy as the
number of position fixes captured increases) or negative (indicating an increase in accuracy as the
0.000
number of position fixes captured increases). Fig. 3
illustrates two cases with high coefficient of determination (R2) values that suggest either of these trends
may be observed. Further, while the R2 values of the
regression lines fit to the fifty position fixes from
Fig. 3 RMSE values for fifty consecutive position fixes collected at a control point in the young coniferous forest, and regression lines drawn to describe
changes ((a) improvement and (b) decline) in static horizontal position accuracy
Slika 3. Vrijednosti srednje kvadratne pogre{ke za pedeset uzastopnih ~vrstih to~aka prikupljenih na kontrolnoj to~ki u mladoj {umi ~etinja~a i regresijske
krivulje povu~ene kako bi prikazale promjene ((a) pobolj{anja i (b) pogor{anja) to~nosti stati~koga horizontalnoga polo`aja
Croat. j. for. eng. 33(2012)1
153
P. Bettinger and K. Merry
Static Horizontal Positions Determined with a Consumer-Grade GNSS Receiver ... (149–157)
Table 3 Difference in RMSE (m) from one position fix collected to an average of X position fixes (up to 50, in steps of 10) collected per visit to three forest
types on the Whitehall Forest GPS Test Site (Georgia, USA)
Tablica 3. Razlika u srednjoj kvadratnoj pogre{ci (m) od jedne polo`ajne ~vrste to~ke do prosje~ne vrijednosti za X polo`ajnih ~vrstih to~aka (do 50, u
koracima po 10) prikupljenim po jednom snimanju unutar razli~itih tipova {uma istra`ivanoga podru~ja Whitehall (Georgia, SAD)
Difference between one position fix collected and X position fixes, m – Razlika izme|u jedne polo`ajne ~vrste to~ke i X polo`ajnih ~vrstih to~aka, m
Forest type – Vrsta {ume
X = 10
X = 20
X = 30
X = 40
X = 50
Young coniferous – Mlada {uma ~etinja~a
–0.126
–0.252
–0.381
–0.477
–0.568
Older coniferous – Starija {uma ~etinja~a
0.008
0.002
–0.024
–0.034
–0.053
Deciduous – [uma lista~a
0.031
0.110
0.160
0.193
0.184
each visit ranged from 0.55 to 0.70 on average, some
visits produced highly linear trends (R2 > 0.90),
while some visits did not show any trend (R2 = 0.00).
However, the percentage of days with regression
slope values that were within one standard deviation of the mean was very high for all three forest
types (Table 2). In the young coniferous forest, only
5.4% of the regression slope values were below one
standard deviation from the mean, and only 2.3%
were one standard deviation above the mean. In the
older coniferous forest, only 3.4% of the regression
slope values were below one standard deviation from
the mean, and only 5.0% were one standard deviation above the mean. And in the deciduous forest,
only 2.0% of the regression slope values were one
standard deviation below the mean, while only 7.4%
were one standard deviation above the mean. Further,
in the young coniferous forest, the trend during the
spring season (a slight increase in static horizontal
position accuracy with increases in numbers of position fixes) was significantly different (p < 0.05) than
the trends observed in the other seasons of the year.
No other significant differences among the seasons
were observed with regard to the young coniferous
forest. No significant differences (p < 0.05) among
the seasons were observed with regard to the older
coniferous forest and the deciduous forest. So while
it seems that static horizontal positional accuracy does
not significantly change with an increasing number
of position fixes used to determine a position’s location (leading to a decision not to reject H1), the results
are not entirely conclusive, and the season of year
may influence results for some forest types (e.g.,
young coniferous forests), where there is a relatively
high density of trees per unit area that are also relatively short.
Due to the high level of variation among RMSE
values observed each day, statistical tests designed
to examine the difference between the first position fix
RMSE and an average RMSE of a larger set of position fixes all show no significant differences among
the mean values. However, if one were to simply
examine the difference in static horizontal position
154
accuracy (as represented by RMSE values) between
the first and an average of a larger set, trends do
emerge (Table 3).
Through this analysis, we find that the difference
in RMSE between the first position fix and an average of fifty position fixes is over 0.5 m in the young
coniferous forest, which suggests that a larger set (at
least 40 or 50) of position fixes would be necessary in
the young coniferous forest to better describe a static
horizontal position. In examining the results related
to the older coniferous forest, we find very little
difference, on average, between the first position fix
collected and the average of larger sets of position
fixes. In this case, where trees are taller and the forest
is less dense, a static horizontal position could be
estimated just as accurately with one position fix as
with a larger set of position fixes (using the receiver
tested in this research, of course). In the older deciduous forest we found that static horizontal position
accuracy tended to decrease slightly, to about 0.2 m
worse after averaging fifty position fixes. Therefore,
as with the older coniferous forest, a static horizontal
position could be estimated just as accurately with
one position fix as with a larger set. Given these observations, we suggest rejecting the second hypothesis, which proposed that the trends do not differ
by forest type or by density of trees per unit area.
4. Discussion –Rasprava
In previously published research involving the
data used here (Bettinger and Fei 2010), we found
that static horizontal position accuracy was significantly different in deciduous, older coniferous, and
younger coniferous forests, regardless of the season.
The consumer-grade receiver that was tested determined static horizontal positions that were consistent with other similar devices tested in the same
area, and however it was observed that trends in
individual position fix values were evident during
visits to the control points. Therefore, this analysis
was conducted in order to delve into the trends that
Croat. j. for. eng. 33(2012)1
Static Horizontal Positions Determined with a Consumer-Grade GNSS Receiver ... (149–157)
were observed during individual visits to control
points in three types of forests in the southern United
States.
When using low-cost consumer-grade GNSS receivers, fifty position fixes seems to be the most one
would need to determine a horizontal position. In
fact, in some cases (older, less dense forests), one
position fix may return an estimated position that
would be just as accurate as the average of a larger
set. However, we have shown that younger and more
dense coniferous forests (with shorter trees) may
require an average of 40 – 50 position fixes to better
describe the horizontal position, if an improvement
of 0.5 m of accuracy were important. These suggestions are for management applications, of course.
When studying the effects of terrain, vegetation, and
weather on the accuracy of positions determined by
a GNSS receiver, one would want to collect at least
fifty position fixes given the variability that can be
observed within a 2 – 3 minute span of time.
One obvious limitation of this work is that a
single GNSS receiver was studied, and it was a relatively low-cost device (around $ 400 USD). Unfortunately, time and funding constraints influenced
the protocols developed for the study. We acknowledge that an assessment of a larger set of GNSS
receivers in the manner described here would provide further evidence of trends in position fix accuracy. The more troubling aspect of this enhancement
is the time required to perform a long-term study.
For the work presented here, 20 minutes per day
were required for field data collection purposes. With
each additional receiver or each change in parameter
setting, 20 more minutes would be required per day.
We are not implying that this type of research is
impossible to conduct, however, receiver manufacturers and government agencies seem reluctant to
invest in these types of forestry studies. In our case,
the research was unfunded, therefore while improvements to the study design were considered, given
time constraints, many were not pursued.
5. Conclusions – Zaklju~ci
In an assessment of the changes in static horizontal position accuracy of a single low-cost, consumer-grade GNSS receiver, we failed to reject a hypothesis that static horizontal position accuracy does not
significantly change with increasing numbers of position fixes collected. However, we favor rejecting
the hypothesis that trends do not differ by forest
type or by density of trees per unit area. Therefore,
we suggest that when using a GNSS receiver similar
to the one we studied, static horizontal positional accuracy does not significantly change with an increasCroat. j. for. eng. 33(2012)1
P. Bettinger and K. Merry
ing number of position fixes used to determine a
position’s location (leading to a decision not to reject
H1). However, the results are not entirely conclusive,
and the season of the year may influence results for
certain forest types (e.g., young coniferous forests).
Daily visit trends in the improvement (or decline) of
static horizontal position accuracy for three forest
types were observed over the long-term study. We
found that the static horizontal position accuracy in
the young coniferous forest, on average, improved
from that determined by a single position fix to that
determined by a set of fifty position fixes. A much
more minor decline in accuracy was noted in the
deciduous forest, and no trend was observed in the
older coniferous forest.
Acknowledgements – Zahvala
We appreciate and value the thoughtful concerns
of the anonymous reviewers of this manuscript.
6. Reference – Literatura
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2009: An accuracy assessment of positions obtained using
survey-grade and recreational-grade Global Positioning
System receivers across a range of forest conditions within
the Tanana Valley of Interior Alaska. Western Journal of
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Bettinger, P., Fei, S., 2010: One year’s experience with a
recreation-grade GPS receiver. International Journal of
Mathematical and Computational Forestry & Natural-Resource Sciences 2(2): 153–160.
Bolstad, P., Jenks, A., Berkin, J., Horne, K., Reading, W. H.,
2005: A comparison of autonomous, WAAS, real-time, and
post-processed Global Positioning Systems (GPS) accuracies in northern forests. Northern Journal of Applied Forestry 22(1): 5–11.
Danskin, S. D., Bettinger, P., Jordan, T. R., 2009a. Multipath
mitigation under forest canopies: A choke ring antenna
solution. Forest Science 55(2): 109–116.
Danskin, S. D., Bettinger, P., Jordan, T. R., Cieszewski, C.,
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hardwood forest: Exploring low-cost solutions for forestry
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9–16.
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canopies. Journal of Forest Research 8(2): 103–110.
Keskín, M., Say, S. M., Keskín, S. G., 2009: Evaluation of a
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the forest environment. Croatian Journal of Forest Engineering. 29(2): 189–199.
Pirti, A., Gümüs, K., Erkaya, H., Hosbas, R. G. 2010: Evaluating repeatability of RTK GPS/GLONASS near/under
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Horizontal measurement performance of five mapping-grade Global Positioning System receiver configurations
in several forested settings. Western Journal of Applied
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Wing, M. G., Karsky, R., 2006: Standard and real-time accuracy and reliability of a mapping-grade GPS in a coniferous western Oregon forest. Western Journal of Applied
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Sa`etak
Stati~ke horizontalne pozicije odre|ene prijemnikom GNSS (korisni~ke vrste):
procjena broja potrebnih ~vrstih to~aka
Ciljevi su ovoga rada sadr`ani u utvr|ivanju mijenjanja to~nosti stati~koga horizontalnoga polo`aja s obzirom na
broj ~vrstih to~aka prikupljenih tijekom snimanja na poznatoj kontrolnoj to~ki. Hipoteze su sljede}e:
H1: To~nost stati~koga horizontalnoga polo`aja ne mijenja se zna~ajno s pove}anjem broja ~vrstih to~aka
kori{tenih za odre|ivanje polo`aja.
H2: Kretanja se to~nosti stati~koga horizontalnoga polo`aja, s porastom broja ~vrstih to~aka, ne razlikuju s
obzirom na tip {ume ili gusto}u stabala.
Izme|u rujna 2008. i rujna 2009. godine pomo}u GPS prijamnika Garmin Oregon 300 gotovo svakoga dana
prikupljani su podaci u raznolikim stani{nim uvjetima. Stati~ki horizontalni polo`aji snimani su GPS-om u
mladoj {umi ~etinja~a (Pinus taeda), u starijoj {umi ~etinja~a te u {umi lista~a na lokaciji ispitnoga podru~ja
Whitehall Forest, Athens, GA (Atena, Georgia, SAD).
Prosje~ni stati~ki horizontalni polo`aji iznosili su 11,9 m, 6,6 m, i 7,9 m za mladu {umu ~etinja~a, stariju {umu
~etinja~a, odnosno bjelogori~nu {umu.
Tri su kontrolne to~ke (brojevi 6, 31, 37) odabrane za ovo istra`ivanje izme|u raspolo`ivih na istra`ivanom
podru~ju Whitehall (slika 1). Kontrolna to~ka 37 smje{tena je u mladoj borovoj {umi (slika 2), a sastojinski
~imbenici u vrijeme istra`ivanja prikazani su u tablici 1. Kontrolna to~ka 31 smje{tena je u starijoj {umi ~etinja~a,
a kontrolna to~ka 6 u {umi lista~a. Sve tri kontrolne to~ke smje{tene su na povi{enim mjestima (upper slope
positions) u odnosu na okolno podru~je te predstavljaju najbolji izbor za usporedbu izme|u tih triju tipova {ume.
To~ke su obila`ene jednom dnevno tijekom godine, raspored posjeta bio je u potpunosti nasumi~an i svaki je put
prikupljeno pedeset ~vrstih polo`ajnih to~aka.
Nadalje, po{lo se pretpostavkom kori{tenja samo jednoga prijamnika GNSS koji bi imao nepromjenjive radne
parametre tijekom cijele studije kako bi se koristili sli~ni uvjeti prikupljanja podataka.
Snimljeni (neobra|eni) podaci, koji predstavljaju srednju kvadratnu pogre{ku svake odre|ene ~vrste polo`ajne
to~ke, izjedna~eni su linearnom regresijom ~ime se odredio nagib i koeficijent odre|ivanja (R2) linije, a ona najbolje
156
Croat. j. for. eng. 33(2012)1
Static Horizontal Positions Determined with a Consumer-Grade GNSS Receiver ... (149–157)
P. Bettinger and K. Merry
odgovara uklapanju unutar pedeset ~vrstih to~aka svakoga pojedinoga dana snimanja na kontrolnom polo`aju.
Analiza je vo|ena tijekom svih 298 dana istra`ivanja i za svaki od triju tipova {ume.
U tim slu~ajevima jednostavne linearne regresije nezavisna je varijabla srednja kvadratna pogre{ka svake
~vrste to~ke, a zavisna je varijabla broj ~vrstih to~aka (1 do 50). Za potrebe prikazivanja uprosje~ene su vrijednosti
nagiba i koeficijenta odre|ivanja kako bi se moglo zaklju~iti prihva}a li se prva hipoteza, pri ~emu se to~nost
stati~koga horizontalnoga polo`aja ne mijenja zna~ajno s pove}anjem broja polo`ajnih ~vrstih to~aka kori{tenih za
odre|ivanje stvarnoga polo`aja.
S obzirom na mno{tvo od pedeset ~vrstih to~aka prikupljenih prilikom svakoga mjerenja na pojedinoj kontrolnoj
to~ki, ti su podaci smanjeni na {est procjena srednje kvadratne pogre{ke: (1) prva ~vrsta to~ka, (2) srednja
vrijednost prvih deset ~vrstih to~aka, (3) srednja vrijednost prvih dvadeset ~vrstih to~aka, (4) srednja vrijednost
prvih trideset ~vrstih to~aka, (5) srednja vrijednost prvih ~etrdeset ~vrstih to~aka, (6) srednja vrijednost svih
pedeset prikupljenih ~vrstih to~aka. Kako bi bilo jasnije, srednja je kvadratna pogre{ka odre|ena za svaku polo`ajnu
~vrstu to~ku, a potom su vrijednosti pogre{aka uprosje~ene u grupnu prosje~nu stati~ku horizontalnu pogre{ku.
Budu}i da je postojala velika koli~ina varijacija u vrijednostima srednje kvadratne pogre{ke od dana do dana, u
analizi je kori{tena razlika vrijednosti izme|u srednje kvadratne pogre{ke prve ~vrste to~ke i prosje~ne kvadratne
pogre{ke ostalih pet skupina. Ova je analiza osmi{ljena za rje{avanje druge hipoteze, koja je sugerirala kako se
rezultati mogu razlikovati s obzirom na vrstu {ume i obrast.
Na temelju svega navedenoga izvedeni su ovi zaklju~ci: pri kori{tenju prijamnika GNSS tipa ni`ega cjenovnoga razreda to~nost stati~koga horizontalnoga polo`aja ne mijenja se zna~ajno s pove}anjem broja ~vrstih to~aka
kori{tenih za odre|ivanje lokacije polo`aja ({to vodi do zaklju~ka da se hipoteza H1 ne odbacuje). Me|utim, rezultati nisu u potpunosti pouzdani jer i godi{nje doba mo`e utjecati na rezultate u pojedinim tipovima {uma (mlada
{uma ~etinja~a). Kretanja dnevnih snimanja u pobolj{anju (ili pogor{anju) to~nosti stati~koga horizontalnoga
polo`aja za tri tipa {uma promatrana su kroz dugotrajnu studiju. Utvr|eno je da se to~nost stati~koga horizontalnoga polo`aja u mladoj {umi ~etinja~a u prosjeku pobolj{ala od one odre|ene jednom ~vrstom to~kom do one odre|ene pomo}u pedeset ~vrstih to~aka. Mnogo manji pad to~nosti utvr|en je u listopadnoj {umi, dok nikakva kretanja
to~nosti nisu otkrivena u starijoj {umi ~etinja~a.
Klju~ne rije~i: globalni navigacijski satelitski sustavi, to~nost stati~koga horizontalnoga polo`aja, srednja
kvadratna pogre{ka, linearna regresija
Authors’ address – Adresa autorâ:
Received (Primljeno): March 07, 2011
Accepted (Prihva}eno): October 01, 2011
Croat. j. for. eng. 33(2012)1
Prof. Pete Bettinger, PhD.
e-mail: pbettinger@warnell.uga.edu
Krista Merry
Research Professional
e-mail: kmerry@warnell.uga.edu
University of Georgia
School of Forestry and Natural Resources
180 E. Green Street
Athens, GA 30602
USA
157
Subject review – Pregledni rad
Opening-up of Forests for Fire
Extinguishing Purposes
Andrea Majlingová
Abstract – Nacrtak
Information on the existence of forest roads as well as their quality is important not only for
planning forest management activities, but also for fire management, which includes fire
risk assessment and fire suppression. In the case of fire, the level of forest opening-up has a
significant influence on the attendance time of fire brigades. Not sufficiently developed road
network is often reflected on the elongation of fire-fighting attack and exactingness of shuttle
water relay. Therefore, the level of forest opening-up is an important indicator and factor
affecting the promptness of fire-fighting activities and further fire spreading, because forest
roads also represent a natural barrier against fire.
A simple approach to the assessment of the level of forest opening-up has been introduced
from the aspect of terrain accessibility for the available mobile fire apparatus with the use of
GIS and GNSS technologies. First, the forest road network was mapped using the GNSS
technology, and then the information on the quality of particular roads was collected. These
data were processed in the ArcGIS 9.3 environment and as a result the geodatabase was
created. It was later used to process the opening-up analysis in IDRISI Taiga environment.
The opening-up analysis was performed for the Hrabusice forest management district,
located in the karst area of the Slovensky raj National Park and the available mobile fire
apparatus – pumping appliance CAS 32 on Tatra 148 chassis and forest special UNIMOG
on Mercedes chassis.
The objective of the opening-up analysis was to identify the zone where the terrain is
accessible for mobile fire apparatus and where fire hose piping is admissible. It was based on
computation of the maximum range of fire hose piping (maximum sidelong distance), road
spacing and the index of forest opening-up.
The results of this analysis are valuable as a support for decision making for foresters dealing
with forest protection, road planning and construction, for fire brigades in planning fire
attacks, as well as for risk managers and crisis managers.
Keywords: Fire extinguishing, forest fire, GIS, GNSS, opening-up
1. Introduction – Uvod
The intensive exploitation of natural resources
gives rise to significant claims of forest management
oriented not only to sustaining and improving of
wood production functions of forest, but also towards
its non-production functions, such as soil protection,
hydrological control, landscape architecture, health
and recreation.
Forest fires are among the most harmful factors in
forestry representing the highest risk for fulfilling
the objectives of forest management planning.
Croat. j. for. eng. 33(2012)1
In the period 2000–2010, there occurred 4 373
forest fires in Slovakia that destroyed about 5 831 ha
of forests (JRC Scientific and Technical Report 2010).
This is the reason to incorporate the effective fire
protection system into a system of multi-resource
forest management. The most effective fire protection is effective prevention, and if, however, a fire occurs, it is necessary to establish promptly its location
and provide extinction.
The functional and efficient network of forest roads
is a basic pre-requisite for a sustainable multi-resource
forest management as well as for fire protection.
159
Andrea Majlingová
Opening-up of Forests for Fire Extinguishing Purposes (159–168)
In steep mountainous terrain, where the use of
ground-fire-fighting machinery (mobile fire apparatus) is required, the operational facilities of this machinery (mainly its working range) as well as the access
to the fire place are the limiting factors (Chromek
2006).
In Slovakia, 3 types of mobile fire apparatus are
commonly used: pumping appliance CAS on Tatra
148 and Tatra 815 chassis and forest special UNIMOG
on Renault or Mercedes chassis.
The pumping appliance is suitable for extinguishing fires on public roads of 1st and 2nd quality class
and on reinforced forest roads (in Slovakia 1L, 2L
class forest roads in accordance with STN 73 6108).
Due to its technical parameters, the UNIMOG is also
suitable for extinguishing fires on hauling roads (with
the longitudinal slope from 10 to 12%).
This paper deals with the assessment of opening-up of the area of Hrabusice forest management
district for the purposes of extinguishing fires with the
use of mobile fire apparatus: pumping appliance CAS
32 on Tatra 148 chassis and forest special UNIMOG
on Mercedes chassis.
The choice of fire apparatus was not oriented to
the latest and most powerful machine, but to the
model actually used by fire brigades acting in this
territory.
2. Problem – Problem
Effective forest fire prevention is a pre-requisite
for good forest management in fire prone areas. To
have a sufficiently developed road network of good
quality that can be used for efficient fire-fighting is a
sign of well-done fire prevention that can lead to
reduction of fire vulnerability in that territory.
Planning of forest roads is commonly oriented to
assigning the fundamental management activities in
the forest and to reducing the costs and environmental impacts of timber logging. Nowadays, the
analyses of forest opening-up are performed mainly
as a part of timber logging process optimization. For
this purpose the computer aided or GIS approaches
are used. Numerous authors have been concerned
with these problems for many years.
Tan (1999) was interested in locating forest roads
by a spatial and heuristic procedure using microcomputers.
Tu~ek and Pacola (1999) introduced the algorithms
for tractor and cableway skidding distance modelling on a raster digital terrain model in GIS environment.
Adams et al. (2003) published an approach to the
modelling of steep terrain harvesting risk using GIS.
160
Eriksson and Rönnqvist (2003) presented a decision support system for transportation and route
planning in Sweden as well as the Akarweb – web
based planning system.
Andreson and Nelson (2004) published an optimization approach to the projecting vector-based
road network based on the shortest path algorithm
applicable in GIS environment.
Gumus at al. (2007) introduced a new network
planning approach developed for wood-harvesting.
GIS was also used for data evaluation and planning
process. It was applied to Catak Forest District area.
Contreras and Chung (2007) published in their
work a computer approach to finding optimal long
landing location and analyzing influencing factors
for ground-based timber harvesting.
Slan~ík at al. (2009) introduced the model for
optimization of timber logging and transportation
technologies regarding the ecological criteria. It was
created using GIS and EMDS tools.
In 2010, Kühmaier and Stampfer introduced a
GIS based evaluation model designed to select the
optimal timber harvesting system. The model has
been demonstrated in steep terrain in the South of
Lower Austria.
The requirements related to fire extinguishing
activities in the forest are not well implemented into
to forest management planning. However, there are
few works dealing with the problem of opening-up
analyses as a simultaneous combination of requirements related to forest management and fire risk management.
Johnsson at al. (1998) published a scientific paper
dealing with the problem of integration of wildfire
into strategic planning for Sierra Nevada forests.
Gonzáles at al. (2005) dealt with the problem of
integrating fire risk in forest management planning
on landscape-level perspective in Spain.
Acuna at al. (2010) introduced an approach to the
integrated spatial fire and forest management planning. They applied it in the boreal forest region of the
province of Alberta in western Canada.
In Slovakia, there are also activities related to the
planning and reconstruction of fire protection roads,
e.g. Dvor{~ák and Bohmer (2006); Antalová (2010),
or fire stop systems (Hlavá~ at al. 2007).
In our conditions only B`hmer and Dvor{~ák
(2006) dealt with the problem of optimization of
forest opening-up for the purpose of fire extinguishing. In the optimization process they considered a
pumping appliance »CAS 32« and a portable pump
»PS 12«. The analysis was performed by the classic
mathematical approach. In the calculation they also
Croat. j. for. eng. 33(2012)1
Opening-up of Forests for Fire Extinguishing Purposes (159–168)
included the friction losses because of different terrain slope.
The implementation of GIS methods into the analysis allows performing parallel processing of several inputs resulting in increasing time and cost efficiency in sense of reduction of exerted work, time
saving and reduction of errors caused by a subjective
view on the analyzed phenomenon.
3. Material and methodology – Materijal i
metodologija
3.1 Experimental area – Podru~je istra`ivanja
On the basis of the results of fire danger assessment of the forests of the Slovak Republic (Majlingová 2007), the territory of Slovensky raj National
Park, and hence also Hrabusice management district, is the region with the highest degree of fire
danger in Slovakia. This is mainly so because of the
climate conditions, forest species composition, inaccessible terrain – very low level of forest opening-up,
number of tourists and people living in poverty (Majlingová 2010).
The Slovensky raj National Park is situated in the
north-eastern part of the Slovenske Rudohorie Mts.
near the Low Tatras Mts. Fig. 1 shows the location of
the experimental area. The geological ground consists of limestone and dolomite that allow the creation of karst formations. The predominant soil types
are rendzinas, pararendzinas and lithosols (80 – 90%
of the area). Forest covers about 75% of the area. The
most represented tree species is spruce (50%), fol-
Andrea Majlingová
lowed by beech (30%). The climate characteristics
show that the preponderance of the area belongs to a
moderately cold region with an average annual temperature of 5 – 6 °C. Climate conditions together with
the meteorological situation represent significant factors for fire initiation. The highest fire danger periods are the spring season (March – May) and the
summer season, with the months with the highest air
temperature (July and August).
This region is well-known for an abundance of
canyons, ravines, caves. It is also well known because of well-developed tourism. Every year more
than 300 000 visitors come here.
For fire extinguishing purposes in the experimental area, two types of mobile fire apparatus are commonly used: the pumping appliance »CAS 32« on
Tatra 815 chassis and special forest mobile apparatus
called »UNIMOG« on Mercedes chassis.
3.2 Basic technical parameters of the mobile
fire apparatus – Osnovni tehni~ki parametri
kori{tene vatrogasne opreme
CAS 32 Tatra 148 has an excellent driveability
and quantity of extinguishing substances (6000 l). It
is most commonly used in fires in inaccessible terrain (forest fires, old grasslands, etc.). Pump power
output is 3200 lmin–1 at a pressure of 0.8 Mpa. It is
used to transport members of the fire brigade (1 + 2)
and material as well as pressure, foaming, assistance
and rescue equipment.
Mercedes–Benz UNIMOG is primarily used in
the transport of extinguishing agents (2500 litres of
water and 150 litres of foam) as well as members of
Fig. 1 Location of the experimental area
Slika 1. Lokacija istra`ivanoga podru~ja
Croat. j. for. eng. 33(2012)1
161
Andrea Majlingová
Opening-up of Forests for Fire Extinguishing Purposes (159–168)
the fire brigade (1 + 2) and material together with the
pressure, foaming, assistance and rescue equipment.
This vehicle is suitable to be applied in a harsh and
inaccessible terrain non-passable for another fire
machine.
The technical equipment of both types of apparatus, designed to ground attack, is generally composed of 2 hoses with the diameter of 75 mm (»B«
type) and the length of 20 m, 2 hoses with the diameter of 75 mm and the length of 5 m and 5 hoses
with the diameter of 54 mm and the length of 20 m.
Therefore the total length of the delivery fire hose
piping could be up to 150 m (it is also the maximum
range value).
3.3 Methodology of data collection and
pre-processing in ArcGIS environment
Metodologija prikupljanja podataka i
obrada u ArcGIS-u
In the pre-processing phase, vector layer of the
actual forest road network was obtained using the
position measurement with the Trimble GeoXH GNSS
device as well as information about its current condition obtained by terrain survey. Both sources were
used to create the geodatabase that was later used in
the opening-up analysis.
The position and attributes of forest road network were then corrected on the basis of the orthophotos in ArcGIS environment. The corrections were
done manually by editing the position errors. Pieces
of information on the road owner/user, road category, road and hauling road cover were entered into
the database and changes related to specific sections
of forest road network were proposed.
3.4 Methodology of forest opening-up analysis
in IDRISI Taiga environment – Analiza
otvaranja {uma primjenom softverskoga
paketa IDRISI Taiga
The analysis of forest opening-up was performed
in IDRISI Taiga environment using the functions of
context operators, map algebra and distance analyses.
Fig. 2 Development diagram of the forest opening-up analysis
Slika 2. Dijagram razvoja algoritma za analizu otvaranja {uma
162
Croat. j. for. eng. 33(2012)1
Opening-up of Forests for Fire Extinguishing Purposes (159–168)
Due to the variability of conditions related to water
relay and the direction of extinguishing (upslope or
downslope), both directions of fire extinguishing were
taken into consideration in the calculation. Based on
the calculated maximum range values of the delivery
of fire hose piping, the road spacing was calculated
using the formula published in B`hmer and Dvor{~ák
(2006). The calculated maximum range of delivery of
fire hose piping also determines the zone where
mobile fire apparatus can be applied for fire extinguishing.
The following data were used as the input layers
to the opening-up analysis: digital relief model with
the spatial resolution of 10 m, vector layer of forest
unit borders and vector layer of road network representing the actual situation in spatial distribution
of forest roads in the experimental area, obtained by
road network mapping using the GNSS technology.
The resulting values of the analysis of forest opening-up and extraction for individual forest stands
are shown in the development diagram (Fig. 2).
The first step was the data pre-processing. The
digital relief model was used as a source for the
slope raster calculation – module SURFACE. It was
calculated in percentage. For the purposes of further
analysis it was consecutively converted to the radians
– module TRANSFORM. The vector representation
of forest roads, distributed in the experimental area,
was also converted to the raster representation (module RECLASS) – binary raster (1 – roads suitable to
be used by the mobile fire apparatus, 0 – the other
roads).
The next step was to calculate the cell sloping
distances using map algebra tools (module Image
Calculator). The input raster for this calculation was
the raster of slope converted to the radians.
The calculation was performed based on the formula:
dslope = 10/cos a
(1)
Where:
dslope sloping distance, m
10
resolution of the raster cell, m
a
angle which contains the hypotenuse with
an adjacent leg (or raster of slope in GIS), °
The output raster was used as a friction surface
raster for the calculation of cost distances, using distance operators – module COSTGROW. In the calculation it had been considered with 2 types of analyses.
The first was performed for the pumping appliance
CAS 32 used for extinguishing fires from reinforced
forest roads and the other for the UNIMOG which
uses skidding roads except the reinforced ones.
Croat. j. for. eng. 33(2012)1
Andrea Majlingová
The next step was to calculate the horizontal lengths
of the fire hose piping and road spacing. Providing
that the road spacing is considered as the distance of
its orthographic projections into the horizontal level,
it was necessary to recalculate the appropriate diagonal lengths of the fire hose line onto horizontal
ones according to the following equation. For that
purpose the Map algebra tools (module Image Calculator) were applied.
s
))
(2)
dhoriz = dslope ´ cos (arctg (
100
Where:
dhoriz horizontal distance [m] (cost distance
raster)
dslope sloping distance, m
s
slope, °
The output raster was consecutively reduced (module RECLASS) to the zone of extinguishing using
the mobile fire apparatus – the area opened up for
ground fire extinguishing. The maximum range of
extinguishing zone was determined to 150 m due to
the maximum length of delivery fire hose piping.
Road spacing was calculated from the maximum
horizontal length projections of the fire hose piping
for upslope and downslope ways of water transport
based on the formula:
R = 2 ´ dhoriz
(3)
Where:
R
road spacing, m
Furthermore, range values of the fire hose piping
(sloping length of fire hose piping) were established
for specific forest units, using module EXTRACT as
the functions of Database Query operators.
At the end the area opening-up index [%] was calculated as the ratio between accessible area [ha]/non
accessible area [ha] and the whole experimental area.
4. Results and discussion – Rezultati
s raspravom
The amount of damage caused by forest fires
depends not only on the fire extent and price of
wood destroyed, but much more on the consequential ecological and environmental losses. Fire extinguishing mostly depends on the area opening-up
and terrain accessibility. Effective fire prevention in
forest management is also based on the early fire
observation, prompt fire call and especially on the
terrain accessibility. In fighting forest fires, in addition to early fire call and warning, the accessibility
163
Andrea Majlingová
Opening-up of Forests for Fire Extinguishing Purposes (159–168)
of localities affected by the fire is a crucial factor,
followed by the provision of fire-fighting machinery
and application of fire protection means. In this regard, the forest fund in Slovakia is divided into three
groups: inaccessible area, hardly accessible area and
easily accessible area. To improve the accessibility of
mobile fire appliances, it is necessary to ensure the
systematic development of the forest road network
with the parameters enabling the passage of mobile
fire-fighting machinery. This should be ensured by
legal entities and individuals owning and managing
forests (B`hmer and Dvor{~ák 2006).
In case of fire, the level of forest opening-up also
has significant influence on the attendance time of
fire brigades. Generally, the minimum time for a fire
flaring is 10 minutes.
In mountainous, indented areas, the forest roads
are not suitable for the use of the mobile fire apparatus. This is mainly due to their quality and technical parameters and it is reflected on the elongation of
fire-fighting attack and exactingness of shuttle water
relay.
Consequently, the forest opening-up level can be
considered as an important indicator and factor affecting the promptness of fire fighting activities and
further fire spreading, because forest roads represent
a natural barrier against fire.
Partial results were then introduced leading to
the calculation of opening-up index that expresses
the actual state of the experimental area accessibility
for the selected mobile fire apparatus.
In the calculation of the maximum length of fire
hose piping, the side slope was taken into consideration, as it strongly affects the losses in fire hose
piping according to the recommendation published
by B`hmer and Dvor{~ák (2006).
The maximum length (working range) of the delivery fire hose piping was determined as 150 m, also
taking into consideration the length of its particular
components (technical equipment of the apparatus).
The total range of the fire extinguishing zone is,
therefore, between 0 – 300 m, due to two directions of
extinguishing. However, this only applies in localities where the slope is not steep and the terrain
conditions allow the use of the fire hose piping up to
150 m length. This is possible only in lowlands. In
the mountainous terrain, the sloping distance is shorter and losses in the fire hose piping increase. Then
the road spacing value of 300 m represents only a
theoretical range of fire extinguishing zone. However, for the geomorphological conditions of Slovakia, the optimum road spacing is generally about
400 – 600 m.
Table 1 shows the values of maximum sloping
distance established for the specific forest units in
164
Table 1 Maximum sloping distance values by forest units
Tablica 1. Maksimalne stvarne udaljenosti pristupa povr{ini po odjelima
Forest unit No.
Broj odjela
197
198
199
200
201
202
203
204
205
206
207
208
209
341
345
476
486
Maximum sloping distance, m
Maksimalne stvarne udaljenosti pristupa povr{ini, m
CAS
UNIMOG
959
985
1653
1653
1686
1691
1512
1512
1954
1969
2182
2231
2481
2536
2846
2875
2887
2887
2486
2511
2718
2718
2925
2925
2808
2808
107
157
105
129
105
104
98
134
The results of the calculated sloping distance for the
UNIMOG are presented in Fig. 3.
the area. They were calculated as the distance from
the nearest road to the specific forest units. Only the
maximum values are presented for the forest units
(calculated as the distance from the road to the furthest part of a forest unit).
It should be pointed out here that the methodology of sloping distance calculation processing in
GIS environment could also be considered as the
result of this paper.
Fig. 4 presents the view on opened up forest area
for the UNIMOG fire mobile apparatus. This result
was produced based on the classification of forest
units into categories: 1 – forest unit with the average
sloping distance less or equal to 150 m and 0 – forest
unit with the average sloping distance of more than
150 m. Only the forest units classified as Class 1 are
suitable for fire extinguishing with the mobile fire
apparatus.
The results of opening-up analysis can be best
expressed by the means of opening-up index, which
shows the fact that in case of use of the CAS 32Tatra
148 the experimental area was only 26% opened-up.
In case of use of the UNIMOG, the percentage rate
only increased to 30.5%.
Croat. j. for. eng. 33(2012)1
Opening-up of Forests for Fire Extinguishing Purposes (159–168)
Andrea Majlingová
Fig. 3 Visualization of the results of the sloping distance calculation for UNIMOG, m
Slika 3. Grafi~ki prikaz rezultata izra~unatih stvarnih udaljenosti pristupa povr{ini za UNIMOG, m
Fig. 4 Visualization of the results of forest opening-up analysis for UNIMOG
Slika 4. Prikaz analize otvaranja {uma za UNIMOG
Croat. j. for. eng. 33(2012)1
165
Andrea Majlingová
Opening-up of Forests for Fire Extinguishing Purposes (159–168)
Table 2 Survey of current opening-up in the experimental area
Tablica 2. Postoje}a pristupa~nost terena u istra`ivanom podru~ju
CAS 32
UNIMOG
Extent – Povr{ina, ha Relative rate – Relativni udio, % Extent – Povr{ina, ha Relative rate – Relativni udio, %
Total area – Ukupno
5528.23
100
5528.23
100
Accessible area – Pristupa~no podru~je
1437.34
26
1686.11
30.05
Inaccessible area – Nepristupa~no podru~je
4090.89
74
3842.12
69.5
The present level of forest opening-up of the Hrabusice forest management district is shown in Table 2.
The results presented here refer to the low level of
the area opening-up. This is mainly caused by the
geomorphohological conditions of the experimental
area. This is one of the most significant reasons why
this area is the region with the highest number of
forest fires and with the largest extent of the area
burnt. It also implies the need to apply the aerial
attack in case of fire. However this technology is
more expensive and does not allow keeping a continuous shuttle water relay at the fire site as the mobile
fire apparatus does.
5. Conclusions – Zaklju~ci
The Slovensky raj National Park is known for its
steep terrain, and numerous karst forms as gulches,
ravines and canyons. However, it is also well known
because of the fire occurrence in the area. The forest
fires that occurred in the past affected large areas
and it took several days to extinguish them. Six
people burnt during extinguishing a fire that occurred in this area in 2000. Therefore, mainly because of
the high fire risk in this area, it is necessary to provide the opening-up of this area.
Due to operational tactics, it is generally known
that in the Slovensky raj National Park the aerial
attacks were mainly used for extinguishing fires.
The results presented in this paper confirm the need
for their use based on the low level of the area
opening-up. For this reason the mobile fire apparatus
could only be used for fire extinguishing in areas
that are properly opened up by reinforced forest
roads of good quality.
The advantage of the area opening-up analysis
and evaluation method based on GIS is the fact that
it allows processing of the analysis for any area in a
relatively short time and at low costs, which allows
efficient decision making on fire extinguishing tactics. The other advantage is GIS capability to also
process and combine information about factors that
could not be assessed in the terrain, e.g. because of
smoke curtain.
166
Acknowledgment – Zahvala
This work was supported by the Grant Agency of
the Ministry of Education, Science, Research and
Sport of the Slovak Republic under the contracts No.
VEGA 1/0714/10 andVEGA 1/0313/09.
6. Reference – Literatura
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Adams, J. D., Visser, R. J. M., Prisley, S. P., 2003: Modeling
Steep Terrain Harvesting Risks using GIS. Proceedings of
the second international precision forestry symposium.
Seattle, Washington, 99–108.
Anderson, A. E., Nelson, J., 2004: Projecting vector-based
road networks with a shortest path algorithm. Canadian
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Antalová, M., 2010: Projekt rekon{trukcie protipo`iarnej
lesnej cesty Tajchy In COYOUS 2010: konference mladých
vdeckých pracovníkç. Praha : ^eská zemdlská univerzita v Praze, 155–162.
B`hmer, M., Dvor{~ák, P., 2006: Evaluation and optimization of fire control forest accessing for classic fire-fighting
attack. Proceedings of the 2nd International Scientific Conference – Fire Engineering. Lu~enec, 35–44.
Chromek, I., 2006: Vyu`itie leteckej techniky pri hasení
lesných po`iarov. Monography, Zvolen: Technická univerzita vo Zvolene, ISBN 80-228-1595-0.
Contreras, M., Chung, W., 2007: A computer approach to
finding an optimal log landing location and analyzing
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Eriksson, J., Rönnqvist, M., 2003: Decision support system/
tools: Transportation and route planning: Åkarweb – a web
based planning system. Proceedings of the 2nd Forest Engineering Conference, Uppsala, Sweden, 48–57.
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Reports. Report Nb. 11. Joint Research Centre. Luxembourg: Publications Office of the European Union, European Union 2011. ISSN 1018-5593.
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González, J. R., Palahí, M., Pukkala, T., 2005: Integrating
fire risk considerations in forest management planning in
Spain – A landscape level perspective. Landscape Ecology
20(8): 957–970.
Gumus, S., Acar, H., Toksoy, D., 2007: Functional forest
road network planning by consideration of environmental
impact assessment for wood harvesting. Environmental
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Andrea Majlingová
ného seminára 8. setkání u `ivatelç Idrisi. MZLU Brno,
26–35.
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fire risk assessment of the natural environment. In Fire
engineering proceedings. The 3rd international scientific
conference, Technical University in Zvolen, Slovak Republic, 215–220.
Hlavá~, P., Chromek, I., Majlingová, A., 2007: Vybrané
projekty protipo`iarnej ochrany lesa po vetrovej kalamite.
Monography. Zvolen: Technická univerzita vo Zvolene.
Slan~ík, M., Suchomel, J., Lieskovský, M., Tu~ek, J., 2009:
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Woodworking technique. Zalesina, Croatia, 257–265.
Johnson, K. N., Sessions, J., Franklin, J., Gabriel, J., 1998:
Integrating wildfire into strategic planning for Sierra Nevada forests. Journal of Forestry 96(1): 42–49.
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Sa`etak
Otvaranje {uma radi za{tite od po`ara
Podatak o koli~ini i prostornom razmje{taju {umske prometne infrastrukture va`an je podatak ne samo za potrebe gospodarenja {umama ve} i za planiranje prevencije i za{tite {uma od po`ara. U slu~aju {umskoga po`ara
podatak o prostornom razmje{taju {umske prometne infrastrukture ima velik utjecaj na vrijeme dolaska vatrogasne
postrojbe na mjesto po`ara. Nedovoljno razvijena mre`a {umskih cesta ~esto se odra`ava na produljenje protupo`arne obrane, a samim time i ve}e {tete nastale po`arom. Stoga je podatak o relativnoj otvorenosti {uma va`an
pokazatelj koji utje~e na brzinu protupo`arne za{tite i brzinu {irenja po`ara jer je {umska prometna infrastruktura
ujedno i prirodna barijera koja spre~ava {irenje po`ara.
[umski su po`ari u Slova~koj najve}a prijetnja {umama i {umskomu zemlji{tu te su jedan od glavnih ~imbenika
koji utje~u na (ne)ispunjavanje ciljeva zadanih osnovom gospodarenja. Od 2000. do 2010. godine zabilje`ena su
4373 {umska po`ara u Slova~koj koji su opusto{ili oko 5831 ha {uma i {umskoga zemlji{ta (JRC Scientific and
Technical Report 2010).
Pri planiranju mre`e {umske prometne infrastrukture do sada je naj~e{}e glavni cilj bio zadovoljiti zahtjeve
gospodarenja {uma, a pri tome se najvi{e ra~una vodilo o smanjenju tro{kova pri sje~i i izradi te privla~enju drvnih
sortimenata. Iz toga su razloga analize otvaranja {umskih podru~ja ra|ene uglavnom kao dio optimizacije pridobivanja drva, a zahtjevi vezani uz protupo`arnu za{titu donekle su uzimani u obzir ili uop}e nisu.
U ovom je radu predstavljen jednostavan pristup odre|ivanja relativne otvorenosti {uma iz aspekta pristupa~nosti terena za dostupna vatrogasna vozila koriste}i tehnologiju GIS i GNSS. [umska prometna infrastruktura
snimljena je pomo}u tehnologije GSNN te su tako dobiveni podaci o kvaliteti i u~inkovitosti {umskih cesta. U
ra~unalnom programu ArcGIS 9.3 snimljeni podaci su obra|eni i kao rezultat napravljena je baza podataka koja je
poslije kori{tena za analizu otvaranja istra`ivanoga podru~ja u softverskom paketu IDRISIS Taiga uz primjenu
funkcije algoritama, digitalne zemljovide i analize udaljenosti. Zbog varijabilnosti terenskih uvjeta i smjera ga{enja po`ara u obzir i izra~un uzeta su oba smjera ga{enja po`ara (uz nagib i niz nagib).
Analiza otvaranja izvedena je za gospodarsku jedinicu »Hrabusice« koja ima najve}i indeks opasnosti od po`ara u Slova~koj te je smje{tena u kr{kom podru~ju Nacionalnoga parka »Slovensky raj«. Indeks opasnosti od po`ara
za navedeno podru~je vrlo je velik zbog klimatskih uvjeta, sastava {umskih vrsta (udio smreke 50 %, bukve 30 % i ostale vrste 20 %), nepristupa~nosti terena (vrlo niske relativne otvorenosti), velikoga broja turista (godi{nje vi{e od
Croat. j. for. eng. 33(2012)1
167
Andrea Majlingová
Opening-up of Forests for Fire Extinguishing Purposes (159–168)
300 000 posjetitelja). Najve}a opasnost od {umskih po`ara javlja se u prolje}e (o`ujak – svibanj) te u ljetnim mjesecima za vrijeme najvi{ih temperaturnih vrijednosti (srpanj – kolovoz). Navedena je analiza napravljena za vatrogasna vozila Tarta 148 i Mercedesov Unimog opremljenih vatrogasnom opremom.
Cilj je rada bio analizirati relativnu otvorenost istra`ivanoga podru~ja te definirati nepristupa~na podru~ja za
vatrogasna vozila Tarta 148 i Mercedesov Unimog opremljenih vatrogasnom opremom. Pristupa~nost podru~ja
izra~unata je na temelju maksimalnoga dometa protupo`arnoga crijeva, udaljenosti izme|u {umskih cesta i indeksa
otvaranja {uma.
Efektivna za{tita od po`ara u gospodarenju {umama temeljena je na ranom otkrivanju {umskih po`ara, brzom
dojavljivanju vatrogasnim postrojbama, pristupa~nosti terena i mogu}nosti kori{tenja razli~itih tehnika ga{enja
po`ara. [to se ti~e pristupa~nosti terena u Slova~koj, on je podijeljen u tri grupe: nepristupa~an, te{ko pristupa~an i
lako pristupa~an teren. Da bi se pobolj{ala pristupa~nost terena kada se radi o {umskim po`arima, prijeko je potrebno osigurati planirani razvoj mre`e {umske prometne infrastrukture koja }e mo}i podnijeti prometno optere}enje i
omogu}iti nesmetan i siguran prolazak protupo`arnih kamiona.
Najvi{a je duljina protupo`arnoga crijeva 150 m, uzimaju}i u obzir i duljinu pojedinih njegovih dijelova (tehni~ke opreme). Dakle, ukupni je raspon zone za ga{enje po`ara izme|u 0 i 300 m, s obzirom na to da se gasiti mo`e u
oba smjera. Takav na~in izra~una vrijedi samo za nizine (neznatan popre~ni nagib terena) gdje terenski uvjeti omogu}uju da raspon zone za ga{enje po`ara iznosi 300 m.
Na brdovitom i planinskom terenu zbog popre~nih nagiba terena i gubitaka u cjevovodu najvi{i raspon zone za
ga{enje po`ara od 300 m samo je teorijska vrijednost. Zbog toga i razmaci izme|u cesta od 300 m, na takvim
podru~jima, nisu dostatni za potpunu za{titu. U Slova~koj optimalni razmak izme|u {umske prometne infrastrukture na brdskim i planinskim terenima iznosi izme|u 400 i 600 m.
Ovim su radom dobivene vrijedne spoznaje kao potpora pri dono{enju odluka za za{titu {uma, pri planiranju
novih {umskih prometnica te za vatrogasne postrojbe pri planiranju adekvatne i u~inkovite za{tite {uma od po`ara.
Klju~ne rije~i: ga{enje po`ara, {umski po`ar, GIS, GNSS, otvaranje {uma
Authors’ address – Autori~ina adresa:
Received (Primljeno): December 13, 2010
Accepted (Prihva}eno): March 28, 2011
168
Andrea Majlingová, PhD.
e-mail: amajling@vsld.tuzvo.sk
Technical University in Zvolen
Department of Fire Protection
24 T.G. Masaryka
960 53 Zvolen
SLOVAKIA
Croat. j. for. eng. 33(2012)1
ISSN 1845-5719
9 771845 571000

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