Volume 40 No. 1
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Volume 40 No. 1

Effects of Steel Flexible Tracks on Forwarder Peak Load Distribution: Results from a Prototype Load Test Platform

volume: 40, issue: 1

Steel flexible tracks (SFT) are regularly installed on bogie axles of forwarders to improve traction
and extend trafficability by increasing the contact area between machines and operating surface.
The study quantified dynamic peak loads exerted by a forwarder driving either on wheels or
using additional SFT on its rear bogie axle. To examine load distribution of a full-scale forwarder,
a load test platform was designed and constructed. Three scenarios were tested with the
forwarder unloaded and loaded to quantify load distribution between wheels driven directly over
the steel load test platform (Scenario 1) and SFT when either driven directly over the steel load
test platform (Scenario 2) or when driven over a 20 cm layer of sand placed over the platform
(Scenario 3). The platform proved to be an appropriate measuring device for full-scale tests.
Results indicate that, when operated on the sand layer, SFT (installed on the forwarder’s rear
unloaded axle) decreased dynamic peak loads by about 30% compared to wheels. The use of SFT
on bogie axles of forest machines is recommended to lower soil disturbances, especially through
a reduction of peak loads often responsible for negatively altering soil physical properties.

Development of a Sensorized Timber Processor Head Prototype – Part 1: Sensors Description and Hardware Integration

volume: 40, issue: 1

Forest operations are in constant development to provide increasingly higher standards of
economic and environmental sustainability. The latest innovation trends are concentrated in
the generation, storage and management of data related to the harvesting process, timber
products and logistics operations. Current technologies provide productivity and position, but
only physical parameters are made available for timber products. The possibility of providing
a comprehensive quality evaluation of roundwood early in the supply chain and linking the
information to each log provides a new tool for optimization of the whole forest-timber supply
chain. Current in-field methods for grading logs are based on visual rating scales, which are
subjective, operator-dependent and time-consuming. As an alternative, a sensorized processor
head was developed, featuring the following sensors: near infrared (NIR) spectrometer and
hyperspectral cameras to identify surface defects, stress wave and time of flight sensors to
estimate timber density, hydraulic flow sensor to estimate cross-cutting resistance and delimbing
sensors to estimate branches number and approximate position. The prototype also deployed
an RFID UHF system, which allowed the identification of the incoming tree and individually
marked each log, relating the quality parameters recorded to the physical item and
tracing it along the supply chain. The tested sensors were installed and designed to be independent,
nevertheless, their integrated use provides a comprehensive evaluation of timber
quality. This paper presents the technical solutions adopted, the main hindrances found and
some preliminary results of the operative prototype as tested in laboratory and in forest operational

Comparison of Productivity, Cost and Chip Quality of Four Balanced Harvest Systems Operating in a Eucalyptus globulus Plantation in Western Australia

volume: 40, issue: 1

There have been few comparative harvest system studies to provide a basis to understand the
performance and chip quality of harvest systems used in eucalypt plantations.
The study compared the CTL – cut-to-length method at the stump, WTM – whole tree method
where trees were processed to logs at roadside, IFC-DDC – infield chipping using a debark/
delimb/chipper, IFC-F/C – infield chipping using a separate flail and chipper harvest systems
on a single site in south-west Western Australia.
The WTM and IFC-F/C harvest systems were the most productive. The productivity of the
CTL and IFC-DDC harvest systems was about 25% less than that of the other harvest systems.
The CTL harvest system produced wood at the highest cost resulting from it having a large
number of machines without a correspondingly high productivity level. However, the CTL
harvest system has advantages over the other systems through retaining evenly distributed
logging residues, low machinery impact on the site and flexibility to add or subtract machines
as conditions change.
Two limitations of this study were that the harvest systems were only compared at a single
mean tree size and operator performance differences may have influenced harvest system
productivity. Previous studies have found that the balance of machines in a harvest system
can change with changes in mean tree size. This is an area where further research is required.
Wood chip samples from three of the four harvest systems did not meet the company chip
specifications. However, the deviations from the specifications were minor.

Costing the Forest Operations and the Supply of Hardwood in Tennessee

volume: 40, issue: 1

The purpose of this paper is to assess the delivered cost of pulpwood from natural hardwood
stands in the State of Tennessee using forest operations supply chain analysis. The study is
based on primary production and equipment data collected from logging firms using a statewide
in-depth harvesting and transportation survey. Survey results were used to develop estimates
for the delivery cost of hardwood pulpwood removed per green tonne unit hour. Findings
revealed not only the variability of inputs attached to costing harvesting operations, but
also the difficulty in identifying one typical harvest system for the state. This may be explained
by the very diverse operating conditions and systems, as well as the low stumpage prices and
high cost of harvesting and delivery that are predominantly managed by small scale operations.
Results have shown that the cost of harvesting a tonne of wood for a distance of up to 50 km
ranges from an average minimum of $43 per tonne to an average maximum of $51 per tonne.
After this distance, the cost increases exponentially. The fact that this study is the first for the
state that looks at the operations logistics indicates the lack of available knowledge of the true
cost incurred by operators that may have a lasting impact not only on the continuity of logging
operations but also the sustainability and availability of forest products and workforce.

South African Pine Cut-to-Length Harvesting: an Analysis of Fibre Loss and Productivity

volume: 40, issue: 1

A study was conducted in Pinus elliottii and Pinus patula clear-felling stands in the Southern
Cape and Mpumulanga forestry regions of South Africa. A hybrid harvester was observed
over four compartments in a cut-to-length system in order to assess its productivity as well as
its precision with regards to potential fibre loss while processing Pinus elliottii and Pinus patula
for sawlog production. Potential fibre loss results show that the harvester contributes minimally
through inaccurate cross-cutting, accounting for 1.5% of the total wood volume processed.
Converted to a cost, this indicated losses up to € 0.18 m–3 for P. elliottii and € 1.61 m–3
for P. patula. Additionally, the machines were found to be more productive when working with
P. elliottii (32.12 m3 SMH–1) than P. patula (17.55 m3 SMH–1). Based on these findings, the
loss was estimated at up to € 22 650 and € 101 530 y–1 for P. elliottii and P. Patula, respectively.
Species showed to have a significant impact on the processing accuracy, with cross-cutting of
P. patula stems being less precise than P. elliottii. This was attributed to the species’ tendency
to grow thicker branches, although differences in harvesting conditions could have contributed.
Results suggest that harvesting P. patula stands in a CTL system requires more caution since
these can be associated with higher economic losses, and lower productivities. Considering the
recent growth of mechanised CTL harvesting, this study hopefully aids in exploring the efficacy
of a system, which has gone largely untested to date in South African conditions.

Productivity and Utilization Benchmarks for Chain Flail Delimber-Debarkers-Chippers Used in Fast-Growing Plantations

volume: 40, issue: 1

The study developed robust benchmark figures for the performance of delimber-debarker-chippers
in fast-growing eucalypt plantations, through the analysis of an exceptionally large database
that combined automatically-captured and user-input records. Data for three Peterson
Pacific DDC 5000 H units operated by the Brazilian company Fibria Cellulose were captured
continuously for three years, from 2015 to 2017. During this time, all study machines ran
triple-shift and clocked over 25 000 hours each. The consolidated record included information
for 79 858 delay events, with an average duration of 0.55 hours per event. Delay time accounted
for 57% of total worksite time: mean utilization was therefore 43%. Maintenance was
the most important cause of delays, and accounted for 22% of total worksite time. Interaction
delays came second, and represented 20% of total worksite time. Mean productivity was
88 solid m3 ub (under bark) per productive machine hour (PMH) or 39 solid m3
ub per scheduled machine hour (SMH), depending on whether delay time was excluded or included in the
calculation. The gap between the most efficient and the least efficient operator was 22% and
26% for scheduled productivity and utilization, respectively (this difference was calculated by
taking the figures for the lowest performer as a basis). While the exact productivity figures
reported here may reflect the exceptionally favorable conditions encountered in rationallymanaged
South American plantations, the dynamics revealed in this study may have general
validity and could offer precious insights for rationalizing a whole range of similar operations.

A Plackett-Burman Design to Optimize Wood Chipper Settings

volume: 40, issue: 1

The wood-chipping process is affected by several factors, notably chipper settings and wood
characteristics. It is often difficult to test all of these factors in a full factorial experimental
plan, due to the large number of trials required. On the other hand, a screening design of the
experiment makes it possible to manage a large number of variables in a small number of trials.
Hence, this approach is used to test six factors, in order to optimize the productivity and
chip quality of a drum wood-chipper. These factors are: feeding speed, screen size, PTO-speed,
wood species, wood moisture content, and wood diameter. Productivity was significantly affected
by screen size, while chip quality was related to feeding speed, screen size, PTO-speed,
and wood species. The results suggest that the optimal configuration can be achieved by adjusting
feeding speed, the PTO-speed, and the wood species, as these settings maximize chip
quality. Screen size requires further analysis, as larger sizes increase productivity but reduce
quality, while the opposite is true for smaller sizes. Thus, the optimal screen size requires a
consideration of costs and benefits that may change according to the retail price of premium
and regular wood chips, and production costs.

Impacts of a High-Capacity Truck Transportation System on the Economy and Traffic Intensity of Pulpwood Supply in Southeast Finland

volume: 40, issue: 1

High-capacity transportation (HCT) of roundwood is a road transport concept that is currently
being demonstrated in Finland and Sweden. In Finland, HCT trucks are in most cases
unable to access roadside storages, but they are expected to bring cost savings in highway
transportation between transshipment terminals and mill yards. Evaluating the optimal solutions
is challenging due to the complexity of the transportation systems. This paper presents a
dynamic simulation model, SimPulp, which was developed to generate information about the
impacts of substituting HCT for a part of the present pulpwood transportation system. A case
study in the area of the most intensive pulpwood use in Finland was conducted. The results
indicate that HCT has potential for reducing transport costs and especially the traffic intensity
of roundwood procurement in the studied area. The economic advantages of pulpwood HCT
could be more significant in a larger area or in the use of inter-terminal backhauling.

Attitudes of Small and Medium-Sized Enterprises towards Energy Efficiency in Wood Procurement: A Case Study of Stora Enso in Finland

volume: 40, issue: 1

Stora Enso Wood Supply Finland (WSF) was certified to the ISO 50001 Energy Efficiency
Management System standard in 2015. At Stora Enso WSF, the goal is to improve energy
efficiency by 4% by 2020 from 2015. Improving the energy efficiency of wood procurement
(i.e. logging and timber trucking) enterprises is currently one of the main focus areas for energy
efficiency development at Stora Enso WSF. In order to clarify its state-of-the-art in the
business of wood procurement enterprises at Stora Enso WSF, logging and timber-trucking
entrepreneurs were interviewed in November and December 2017. The survey data consisted
of 25 logging and 25 timber-trucking entrepreneurs. The coverage rate of both entrepreneur
groups was 73.5% in the survey. The results indicated that timber-trucking enterprises highlight
more energy efficiency and fuel efficiency than logging enterprises. For instance, the
timber-trucking entrepreneurs underscored more energy efficiency in their acquisition decisions
of new vehicles and the greater role of fuel efficiency in the energy-efficient business than
logging entrepreneurs during 2016 and 2017. Furthermore, the survey results revealed that
logging and trucking enterprises can improve energy efficiency in their business by organizing
more energy efficiency education (i.e. economical and anticipated driving training) for
their machine operators and truck drivers. There is a positive attitude towards energy efficiency
among both logging and timber-trucking entrepreneurs. This creates a solid background
to deepen and continue energy-effective work in the wood supply chain between the enterprises
and Stora Enso WSF in the future.

Application of Black-Bridge Satellite Imagery for the Spatial Distribution of Salvage Cutting in Stands Damaged by Wind

volume: 40, issue: 1

Salvage logging is performed to remove the fallen and damaged trees after a natural disturbance,
e.g., fire or windstorm. From an economic point of view, it is desirable to remove the
most valuable merchantable timber, but usually, the process depends mainly on topography
and distance to forest roads. The objective of this study was to evaluate the suitability of the
Black-Bridge satellite imagery for the spatial distribution of salvage cutting in southern Poland
after the severe windstorm in July 2015. In particular, this study aimed to determine which
factors influence the spatial distribution of salvage cutting. The area of windthrow and the
distribution of salvage cutting (July–August 2015 and August 2015–May 2016) were delineated
using Black-Bridge satellite imagery. The distribution of the polygons (representing
windthrow and salvage cutting) was verified with maps of aspect, elevation and slope, derived
from the Digital Terrain Model and the distance to forest roads, obtained from the Digital
Forest Map. The analysis included statistical modelling of the relationships between the process
of salvage cutting and selected geographical and spatial features. It was found that the higher
the elevation and the steeper the slope, the lower the probability of salvage cutting. Exposure
was also found to be a relevant factor (however, it was difficult to interpret) as opposed to the
distance to forest roads.

Operator Exposure to Noise and Whole-Body Vibration in a Fully Mechanised CTL Forest Harvesting System in Karst Terrain

volume: 40, issue: 1

In recent decades fully mechanised cut-to-length forest harvesting systems have spread from
flat and gentle to steep and rough terrain. To analyse the potential adverse impact of these
changes on operator health, an observational study of exposure to noise and whole-body vibration
(WBV) was carried out in karst terrain. The results showed that, in contrast to exposure
to noise, the exposure of harvester and forwarder operators to WBV exceeds the daily exposure
action value specified in the European Directive. Differences between work sites may contribute
up to 8.7 dB(A) to noise exposure and up to 0.28 m/s2 and 6.0 m/s1.75 to WBV exposure
when working with forwarders and harvesters. Aside from technical upgrades of machines,
reduction of exposure to both WBV and noise, while simultaneously maintaining high productivity,
requires careful selection of work sites and adapted work organisation.

Automated Volumetric Measurements of Truckloads through Multi-View Photogrammetry and 3D Reconstruction Software

volume: 40, issue: 1

Since wood represents an important proportion of the delivered cost, it is important to embrace
and implement correct measurement procedures and technologies that provide better wood
volume estimates of logs on trucks. Poor measurements not only impact the revenue obtained
by haulage contractors and forest companies but also might affect their contractual business
relationship. Although laser scanning has become a mature and more affordable technology in
the forestry domain, it remains expensive to adopt and implement in real-life operating
conditions. In this study, multi-view Structure from Motion (SfM) photogrammetry and
commercial 3D image processing software were tested as an innovative and alternative method
for automated volumetric measurement of truckloads. The images were collected with a small
UAV, which was flown around logging trucks transporting Eucalyptus nitens pulplogs.
Photogrammetric commercial software was used to process the images and generate 3D models
of each truckload. The levels of accuracy obtained with multi-view SfM photogrammetry and
3D reconstruction obtained in this study were comparable to those reported in previous studies
with laser scanning systems for truckloads with similar logs and species. The deviations between
the actual and predicted solid volume of logs on trucks ranged between –3.2% and 3.5%, with
an average deviation of –0.05%. In absolute terms, the average deviation was only 0.5 m3 or
1.7%. Although several aspects must be addressed for the operational implementation of SfM
photogrammetry, the results of this study demonstrate the great potential for this method to be
used as a cost-effective tool to aid in the determination of the solid volume of logs on trucks.

Testing the Applicability of the Official Croatian DTM for Normalization of UAV-based DSMs and Plot-level Tree Height Estimations in Lowland Forests

volume: 40, issue: 1

The Airborne Laser Scanning (ALS) technology has been implemented in operational forest
inventories in a number of countries. At the same time, as a cost-effective alternative to ALS,
Digital Aerial Photogrammetry (PHM), based on aerial images, has been widely used for the
past 10 years. Recently, PHM based on Unmanned Aerial Vehicle (UAV) has attracted great
attention as well. Compared to ALS, PHM is unable to penetrate the forest canopy and, ultimately,
to derive an accurate Digital Terrain Model (DTM), which is necessary to normalize
point clouds or Digital Surface Models (DSMs). Many countries worldwide, including Croatia,
still rely on PHM, as they do not have complete DTM coverage by ALS (DTMALS). The
aim of this study is to investigate if the official Croatian DTM generated from PHM (DTMPHM)
can be used for data normalization of UAV-based Digital Surface Model (DSMUAV) and estimating
plot-level mean tree height (HL) in lowland pedunculate oak forests. For that purpose,
HL estimated from DSMUAV normalized with DTMPHM and with DTMALS were generated and
compared as well as validated against field measurements. Additionally, elevation errors in
DTMPHM were detected and eliminated, and the improvement by using corrected DTMPHM
(DTMPHMc) was evaluated. Small, almost negligible variations in the results of the leave-oneout
cross-validation were observed between HL estimated using proposed methods. Compared
to field data, the relative root mean square error (RMSE%) values of HL estimated from DSMUAV
normalized with DTMALS, DTMPHM, and DTMPHMc were 5.10%, 5.14%, and 5.16%, respectively.
The results revealed that in the absence of DTMALS, the existing official Croatian DTM
could be readily used in remote sensing based forest inventory of lowland forest areas. It can
be noted that DTMPHMc did not improve the accuracy of HL estimates because the gross errors
mainly occurred outside of the study plots. However, since the existence of the gross errors in
Croatian DTMPHM has been confirmed by several studies, it is recommended to detect and
eliminate them prior to using the DTMPHM in forest inventory.

Possibilities to Produce Additional Quantities of Woody Biomass from Small-Scale Private Forests in Croatia, Bosnia and Herzegovina and Serbia

volume: 40, issue: 1

Private forests in Croatia, Bosnia and Herzegovina and Serbia are highly fragmented into
small plots of land with low productivity level and a large number of owners. Nevertheless,
they are recognized in the strategic plans and programs concerning renewable energy as having
a significant potential for woody biomass production. A regional research was conducted
among 350 private forest owners in each of the three South-East European countries, Bosnia
and Herzegovina, Croatia, and Serbia. It analyzed management activities and readiness of
private forest owners to produce additional quantities of woody biomass. Smart regulation
principles were selected as analytical framework in order to understand how the design of
forest policy instruments, based on specific characteristics of the target groups, can contribute
to the improvement of private forest owners’ readiness to mobilize additional quantities of
woody biomass from their forests. The results of this research indicated that although the
majority of private forest owners use their forests for producing firewood to meet their own
needs – 91.2% of private forest owners in Croatia, 85.0% in Bosnia and Herzegovina and
89.7% in Serbia, there is economic interest of private forest owners to produce additional
quantities of woody biomass beyond their own fuelwood household consumption – 43.9% in
Croatia, 45.8% in Bosnia and Herzegovina and 54.8% in Serbia. Moreover, private forest
owners’ socio-demographic characteristics, forest property characteristics and management
objectives significantly impacted the owners’ readiness to produce additional quantities of
woody biomass. The readiness for woody biomass mobilization could be increased by providing
different policy instruments, since this is deemed important by private forest owners. Hence,
forest policy recommendations were proposed that may support the private forest owners’
readiness to produce additional quantities of woody biomass.

Multi-Criteria Decision Analysis (MCDA) in Forest Operations – an Introductional Review

volume: 40, issue: 1

Decision making in forestry is very complex and requires consideration of trade-offs among
economic, environmental, and social criteria. Different multi-criteria decision analysis
(MCDA) methods have been developed for structuring and exploring the decision-making
process of such problems. Although MCDA methods are often used for forest management
problems, they are rarely used for forest operation problems. This indicates that scholars and
practitioners working with forest operations are either unaware of MCDA methods, or see no
benefit in using these methods. Therefore, the prime objective of this review was to make
MCDA methods more intelligible (compared with current level of understanding) to novice
users within the field of forest operations. For that purpose, basic ideas as well as the strengths
and limitations of selected MCDA methods are presented. The second objective was to review
applications of MCDA methods in forest operations. The review showed that MCDA applications
are suitable for forest operation problems on all three planning levels – strategic, tactical,
and operational – but with least use on the operational level. This is attributed to: 1) limited
availability of temporally relevant and correct data, 2) lack of time (execution of MCDA
methods is time consuming), and 3) many operational planning problems are solved with
regards to an economic criterion, with other criteria serving more as frames. However, with
increased importance of environmental and social aspects, incorporating MCDA methods into
the decision-making process on the operational planning horizon (e.g., by developing MCDAbased
guidelines for forestry work) is essential.

Forest Road Planning, Construction and Maintenance to Improve Forest Fire Fighting: a Review

volume: 40, issue: 1

Forest roads play a key-role in fire fighting activities. In fact, all ground-based activities are
strictly related to the presence of forest roads as access to fire edge. In spite of this important
role, forest roads are often planned and built without considering their use in fire fighting, and
this also occurs in literature, where few studies are dedicated to the importance of forest roads
in fire fighting. A well-developed and well-maintained forest road network is the answer to
different needs in fire management. The objective of this review is to clarify basic principles
for obtaining efficient road network also for fire fighting, collecting, defining and resuming
the main roles, the most important aspects and the reported experiences to be taken into account
in forest road network planning and maintenance in fire-prone areas. The most important
themes treated are related to: i) the analysis of the functions of forest roads in fire prevention
and suppression; ii) the importance of forest road planning and building also considering their
importance for protecting forests against fires: iii) the construction and maintenance characteristics
to be considered for building and maintaining an efficient forest road network against
fires; iv) the importance of fire prevention and the related role of forest roads. Special attention
has been dedicated to maintenance activities, because a not well-maintained forest road is a
not efficient forest road, and it represents a useless economic and environmental cost.


Web of Science Impact factor (2023): 2.7
Five-years impact factor: 2.3

Quartile: Q1 - Forestry

Subject area

Agricultural and Biological Sciences