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Harvesting systems and technologies

Productivity Model for Cut-to-Length Harvester Operation in South African Eucalyptus Pulpwood Plantations

volume: 39, issue: 1

There has been a concerted shift from traditional motor-manual and semi-mechanised timber
harvesting systems to mechanised cut-to length (CTL) operations in South Africa. This is
particularly true in Eucalyptus pulpwood felling and processing, South Africa’s largest commercial
wood resources used in the pulp and paper industry. Mechanisation improvements
are typically driven by increasing safety regulations, product quality and productivity concerns
related to traditional harvesting systems. The objective of this study is to develop productivity
models for mechanised Eucalyptus pulpwood CTL felling and processing operations by combining
the results of a number of individual studies done over a period of 24 months in the summer
rainfall areas of South Africa. The study takes into account species, machine type (purpose
built vs. excavator based), silvicultural practices (planted vs. coppiced) and slope. The pooled
data revealed general productivity ranges from 5.16 m3 PMH-1 to 27.49 m3 PMH-1.

 

Productivity and Costs of Harwarder Systems in Industrial Roundwood Thinnings

volume: 39, issue: 1

In several studies, the harwarder has proven to be a more cost-effective wood harvesting system
than the traditional two-machine (harvester-forwarder) system, especially when the average
stem size of the marked stand is relatively small, the removals per hectare/stand low (i.e. the
harvesting site small), and the forwarding distance short. One of the strengths of a harwarder
is considered to be the lower relocation costs compared to the two-machine system. The time
consumption of harwarder relocations have not, however, been reported in the previous harwarder
studies. Metsäteho Oy conducted a follow-up study of harwarders in industrial roundwood
harvesting, and also investigated the relocations of harwarders. A total of five – three
Ponsse Wisent Dual and two Valmet 801 Combi – harwarders were examined in the follow-up
study. The amount of harvested industrial roundwood in the study totalled nearly 30,000 m3.
The cost calculations showed that the harwarder system is more competitive than the twomachine
system when the average stem size of the marked stand is relatively low, i.e. less than
110–170 dm3. Furthermore, harwarders were the most competitive at low-removal harvesting
sites. The proportion of the total working time of harwarders used in relocations between harvesting
sites was 2.5%, and the effective relocation time was, on the average, 1.3 hours/relocation.
The study results underlined that it makes sense to harvest relatively small-removal and
small-diameter thinning stands marked for harvesting with a harwarder while, conversely, it
is more worthwhile to harvest sites with larger removals and trees using a two-machine harvester-
forwarder system, thereby raising the profitability of forest machine business.

Middle-Term Сhanges in Topsoils Properties on Skidding Trails and Cutting Strips after Long-Gradual Cutting: a Case Study in the Boreal Forest of the North-East of Russia

volume: 39, issue: 1

In this work, physical and chemical properties of the upper horizons of podzolic light loamy
soil were investigated 21–23 years after forest cutting. This was after the first shift of long-term,
gradual felling was carried out by tree-length logging in wintertime in mixed conifer stands
of the Middle Taiga of the Arkhangelsk Region in Russia. The increased density of the forest
litter composition was observed. This was especially the case on skidding trails. On the forest
floor of skidding trails subjected to a greater stress caused by timber skidding, lower total
porosity and aeration porosity was observed, in comparison with the cutting strip and natural
forest. It was established that timber skidding during wintertime does not affect the density of
podzolic horizon composition. An inverse pattern was observed here: the total porosity and
the aeration porosity became higher and were close to the optimum values for plant growth
(54.16–52.99% and 15.72–19.97%). In the podzolic horizon on skid roads, comparison to the
natural forest showed a significant reduction of phosphorus mobile forms and an increase in
the amount of absorbed bases, which is the result of grassy vegetation overgrowth and natural
birch regeneration. On skidding trails and cutting strips, the organic matter content and total
nitrogen significantly increased, which is related to a change of light intensity, the composition
of living ground cover and vigorous decompositions of the organic horizon and woody residues.
In cutting areas, a system mosaic of soil cover developed, which differed according to favourable
conditions for tree species regeneration, compared to the control stands.

Tractive Performance of Tyres in Forest Conditions – Impact Assessment of Ground and Tyres Parameters

volume: 39, issue: 1

This article deals with the assessment of traction properties of tyres on forest grounds. The
research was carried out on skid trails located in pine stands. The tested grounds were different
due to the cover of the soil and its mechanical properties. The study also deals with the
evaluation of ways to improve traction by reducing the inflation pressure and using the tyre
chain. The research was carried out using a specialized traction test stand for two tyres (9.5–24
and 400/55–22.5) different in width and tread pattern. The studies showed significant effect
of ground conditions on traction. As a result of changes in the ground conditions, the values
of drawbar force, rolling resistance and tractive efficiency were altered by 25%, 23% and 6%,
respectively. The higher values of the drawbar force and tractive efficiency on all tested trails
were obtained for 400/55–22.5 tyre. Both the use of tyre chains and the reduction of inflation
pressure resulted in the increase in drawbar force and tractive efficiency. A better way to improve
traction properties was the reduction of the tyre inflation pressure, which caused the
increase in drawbar force and tractive efficiency. The use of tyre chains caused an increase in
drawbar force over the entire slip range, while an increase in tractive efficiency has only been
shown for the slip larger than 15%.

Including Exogenous Factors in the Evaluation of Harvesting Crew Technical Efficiency using a Multi-Step Data Envelopment Analysis Procedure

volume: 39, issue: 2

The performance of a harvesting crew in terms of its ability to transform inputs into outputs
is influenced by discretionary factors within the unit’s control, such as the selection of machines
and operators. However, factors associated with the operating environment, such as
terrain slope and tree size that are outside the direct control of management, can also influence
harvesting system efficiency. Using data on forest harvesting operations in New Zealand, this
paper applies an established four-stage Data Envelopment Analysis (DEA) procedure to estimate
the managerial efficiency of independent forest harvesting contractors, while taking into
account the influence of the operating environment. The performance of 67 harvesting contractors
is evaluated using seven inputs, one output (system productivity) and three operating
environment factors in an input-oriented, variable return to scale DEA. The results show that
the operating environment including terrain slope, log sorts and piece size influence the efficient
use of inputs by harvesting contractors. A significant difference is observed between the
mean managerial efficiency of the crews before and after controlling for the influence of the
operating environment, the latter being higher by 11%. This study provides evidence that
without accounting for the influence of the operating environment, the resulting DEA efficiency
estimates will be biased; the performance of crews in favourable operating environment
would be overestimated and those in unfavourable environment underestimated.

Productivity, Efficiency and Environmental Effects of Whole-Tree Harvesting in Spanish Coppice Stands Using a Drive-to-Tree Disc Saw Feller-Buncher

volume: 39, issue: 2

Whole tree harvesting was conducted on two coppice stands with different tree composition
(Q. ilex and Q. pyrenaica) in gentle terrain. Felling and bunching were performed by a
drive-to-tree wheeled feller-buncher with disc saw head. Operations were analyzed on 17 plots
25x25 m2 in order to develop productivity models and to assess operational costs. The study
also aimed at determining biomass collection efficiency and evaluating the impact of the new
harvesting method on the soil, the remaining trees and stumps. The treatment consisted in a
strong coppice thinning leaving standards. Productivity ranged from 2.8 to 4.6 odt/pmh in
the Q. ilex coppice, and from 0.9 to 2.6 in the Q. pyrenaica stand. Tree species, dry weight
per tree and percentage of removed basal area were the main independent variables affecting
productivity. Approximately 50% of the standards showed damages. Most wounds were light,
caused by the drive-to-tree work pattern, followed through GPS tracking. Soil damage was
also light; in no plots, deep disturbances were found. However, most of the stumps were damaged.
Forwarding and chipping productivity and cost were also evaluated. The slash left on
the terrain averaged 3.0 and 1.5 odt/ha in Q. ilex and Q. pyrenaica, respectively, including
scrub debris. As a conclusion, while this heavy feller-buncher can be useful in coppice heavy
thinnings with larger trees, it would be a good option to try lighter disc saw felling heads
mounted on the harvester boom tip, which probably would reach better productivity and reduce
the frequency of stand damage.

Investigation of Log Length Accuracy and Harvester Efficiency in Processing of Oak Trees

volume: 39, issue: 2

Harvester use in broadleaves has recently become more effective economically. However, difficulties
with delimbing have shown that not all harvesting heads are suitable and efficient for
broadleaved species. The typical obstacles are mainly large tree sizes, bends and forks in the
trunks and large branches. For these reasons, it is difficult to obtain specific log lengths according
to the settings in the harvester on-board computer. The objective of the research was
to determine: 1) the accuracy of the log lengths from the bottom, middle and top parts of oak
trees, and 2) harvester efficiency in the utilisation of the trunk for logs. The research was carried
out on 61-year-old oaks from which logs with an expected length of 250 cm were processed.
To achieve this length, a margin of error was set in the harvester computer with minimum
and maximum lengths of 252 and 257 cm. For thinning operations, a Ponsse Ergo harvester
with a H7 harvesting head was used. After harvesting, manual log measurements were carried
out on 280 logs: 69, 142 and 69, from bottom, middle and top parts of the trees, respectively.
The largest share of assortments satisfying the minimum requirement of 250–257 cm was
obtained from the middle part of the trees (93%), followed by bottom logs (91%) and top logs
(88%). The highest frequency of logs, which were too short, were found to be the top logs (9%),
while bottom logs were most often too long (6%); therefore, different length settings should be
applied to limit such inaccuracies. Analysis of the last log from the highest part of the tree
indicated a strong goodness of fit between the top diameter and the DBH; the mean value of
the top diameter was 13.3 cm over bark.

Impact of Season and Harvester Engine RPM on Pine Wood Damage from Feed Roller Spikes

volume: 39, issue: 2

Harvesters have become a common solution for wood harvesting in coniferous and broadleaved
stands. Unfortunately, not every customer will accept logs with damage on the lateral surface
of the roundwood caused by feed roller spikes. The extent of the wood damage caused by the spikes
of harvester heads depends mainly on the type of feed rollers and tree species. The objective of the
study was to investigate the external damage to pine (Pinus sylvestris L.) roundwood from
harvester head spikes depending on the season of the year and harvester engine RPM, as well as
the significance and potential consequences of such damage. The scope of the study also included
an analysis of wood damage depth in three stem sections. The experimental plots selected
were all in an 85-year-old pure pine stand. Logging was performed using a Ponsse Beaver harvester
with an H60e harvester head manufactured in 2006. The mean depth of wood damage at
all the points of measurement was 4.1 mm, while the maximum depth of wood damage totalled
5.3 mm. The depth of wood damage depended on the season of the year in which the logging work
was performed, the harvester engine RPM and the stem section from which the log was processed.
The damage was the deepest during summer operations and the shallowest during winter and
springtime. The differences were statistically significant, however, the difference in the depth of
damage was only 1 mm in average. Deeper wood damage was found at a lower engine RPM.
Wood damage depth differed axially, and the least damage was found in the bottom logs.

Tensile Force Monitoring on Large Winch-Assist Forwarders Operating in British Columbia

volume: 39, issue: 2

The forest industry around the world is facing common challenges in accessing wood fiber on
steep terrain. Fully mechanized harvesting systems based on specialized machines, such as
winch-assist forwarders, have been specifically developed for improving the harvesting performances
in steep grounds. While the mechanization process is recognized as a safety benefit,
the use of cables for supporting the machine traction needs a proper investigation. Only a few
studies have analyzed the cable tensile forces of winch-assist forwarders during real operations,
and none of them focused on large machines normally used in North America. Consequently,
a preliminary study focused on tensile force analysis of large winch-assist forwarders was
conducted in three sites in the interior of British Columbia during the fall of 2017.
The results report that in 86% of the cycles, the maximum working load of the cable was less
than one-third of the minimum breaking load. The tensile force analysis showed an expected
pattern of minimum tensile forces while the forwarders were traveling or unloading on the
road site and high tensile forces when operating on steep trails, loading or traveling. Further
analysis found that the maximum cycle tensile forces occurred most frequently when the
machines were moving uphill, independently of whether they were empty or loaded. While the
forwarders were operating on the trails, slope, travel direction, and distance of the machines
from the anchor resulted statistically significant and able to account for 49% of tensile force
variability. However, in the same conditions, the operator settings accounted for 77% of the
tensile force variability, suggesting the human factor as the main variable in cable tensile force
behavior during winch-assist operations.

Productivity and Cost Analysis of Three Timber Extraction Methods on Steep Terrain in Thailand

volume: 39, issue: 2

Steep terrain harvesting in Thailand has low productivity because of the shortage of suitable
logging extraction methods. Common methods involve extraction using manpower on steep
slopes where machines cannot operate. This study compared the utilization of log chutes against
manpower and mule methods with regard to productivity and cost-efficiency in the same logging
compartment in Northern Thailand. The extraction methods were divided into work elements
and data were collected based on described work cycles. The log chutes clearly had the highest
productivity (2.29 m3/h) compared to the other methods. The hourly cost was lowest using
manpower and the highest cost was using the log chute. However, the unit cost indicated the
most economic method was the log chute (THB 72.40/m3) and the least was using mule extraction.
From a logging contractor point of view, the log chute method helps reduce the number of
working days during the harvesting season and provides a higher profit for business.

Production of Wood Chips from Logging Residue under Space-Constrained Conditions

volume: 39, issue: 2

A study was conducted on chip production from logging residue left after a cable yarder operation.
The logistics were managed with tractor and trailer units (shuttles). The study specifically
dealt with a very difficult case of space constrained operations, further expanding the
knowledge about chip supply in extreme work conditions. The focus of the investigation was
also extended to the shuttles. The study tested a production chain, in which only 3 machines
(1 chipper, 2 shuttles) were used to minimize operational costs. The use of 2 shuttles was decisive,
reducing shuttle delays. The chips produced had an average moisture content of 40.2 ±3.1%.
Particle size distribution shows an unfavorable composition. The content of accepts is as low
as 72%, while oversized particles get up to 5.4% and fines rise to a maximum of 24%. The
estimated net productivity of the whole system was 11.5 t PMH-1, corresponding to a gross
productivity of 11.1 t SMH-1. The cost of the whole operation amounted to 21.2 €t-1.

Dynamic Soil Pressures Caused by Travelling Forest Machines

volume: 39, issue: 2

Machines travelling in forest stands cause dynamic loading of soil, the size of which depends
on a multitude of factors such as terrain ruggedness, machine speed, axle load and tyre inflation
pressure. To decide on harvesting and transport machines suitable for specific field conditions,
it is necessary to have at least some awareness about their dynamic effects on the soil,
which sometimes considerably differ from static values measured on standing machines. The
paper deals with the method of determining dynamic ground pressures according to the given
parameters of vehicle weight and speed. At the same time, it compares dynamic pressures
calculated by using this method with actually measured values.

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.

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.

Cost Analysis of Innovative Biomass Harvesting Systems for Young Dense Thinnings

volume: 40, issue:

The objective was to analyze three innovative harvesting systems for early thinnings and compare forest-to-industry supply costs. FlowConv consists of a harvester equipped with an innovative continuously cutting, accumulating and bunching head (the FlowCut head), a forwarder and a truck to transport loose tree-parts. FlowFix consists of a harvester equipped with the same cutting head but also a bundling unit (the Fixteri system), plus a forwarder and roundwood truck for biomass transport. FlowCin consists of a new conceptual biomass harvester (the Cintoc system) equipped with the same cutting head and a second crane to pass the cut trees from the front of the machine to a bundling unit at the back, plus the same forwarding and trucking units as in the FlowFix system. Empirical data were used to assess the FlowConv system’s performance, while the FlowFix and FlowCin systems’ performance was simulated.

Results indicate that supply costs of the FlowCin system would be 6–10% and 24–29% lower than those of the FlowFix and FlowConv systems, respectively. Thus, it would be more suitable to be equipped with an innovative cutting head, which is up to 100% more efficient than the current commercially available options. Key features of the Cintoc-based system (which minimize possible waiting times during operation) include its buffering cradle and delivery of biomass acquired in two cutting crane cycles to the intermediate delivering crane. The apparent superiority of the FlowCin system is consistent with previous conclusions regarding developments needed to maximize the cost-effectiveness of harvesting young dense stands.

Assessing Cable Tensile Forces and Machine Tilt of Winch-Assisted Forwarders on Steep Terrain under Real Working Conditions

volume: 40, issue:

Winch-assisted forwarders are now commonly accepted as an innovative alternative for extracting wood on challenging terrain. In order to assess safety risks, it is necessary to know the tensile forces in the steel wire rope and their interaction with the machine tilt under real working conditions. In this study, the tensile force and the machine tilt of two winch-assisted forwarders (John Deere 1210E and Komatsu 840TX) were observed for about 15 work hours without delays on two different stands in Austria. The tensile force data and the machine tilt data were separated by work elements. The mean tensile force ranged from 18.1 kN for unloading up to 56.8 kN for loading activities. During the measurements, the cable tensile force exceeded 50% of the minimum breaking strength (MBS) only twice. The maximum observed tensile force was 174.5 kN or 82.7% of the MBS, respectively, which led to a failure of the steel cable. For the machine tilt, a maximum of 80% was measured during loading and driving during loading. John Deere 1210E was operated 31% of the productive work time above the manufacturers tilt limit. For Komatsu 840TX, the manufacturers’ maximum tilt limit was exceeded only twice. The study also showed that peaks with an amplitude of up to 50 kN can occur within a few centiseconds, which highlights the need of high measurement rates, when measuring cable tensile force of winch-assisted machinery. The detailed analysis of the peaks showed that 90% of the pit-to-peak amplitudes ≥20 kN occurred during driving activities. Only 10% of pit-to-peak amplitudes ≥20 kN were measured during loading activities, although loading took about 43.5% of the productive work time. As such, the study results confirm that amplitudes of peaks in tensile force, and hence safety risks, are significantly higher during driving than during loading.

Productivity of a Portable Winch System Used in Salvage Logging of Storm-Damaged Timber

volume: 40, issue:

Storm damages result in serious losses in many regions, primarily by stem breakage or blowdown. Extraction of storm-damaged trees often requires more difficult than normal skidding activities due to obstacles created during the storm. In this study, the productivity of a portable winch was evaluated as a possible alternative to recover storm-damaged timber. Field measurements were conducted in the Alabarda Forest Enterprise Chief located near the city of Kütahya in western Turkey, where storm damage often occurs during the winter season. The time study was implemented in two slope classes (35% and 55%) and two skidding distances (40 m and 60 m). All timber was skidded uphill. A regression mode was developed that related productivity to log volume, ground slope and skidding distance. The highest percentage of total cycle time was observed for skidding logs to the landing. The highest productivity (3.96 m3/hour) was found at the shorter skidding distance (40 m) and the lower ground slope (35%). Statistical analyses indicated that productivity was most highly affected by log volume, followed by skidding distance and ground slope. Larger log loads increased productivity, while both longer skidding distances and steeper slopes reduced productivity.

Evaluation of Different Best Management Practices for Erosion Control on Machine Operating Trails

volume: 40, issue:

Ground-based mechanized forest operations often lead to increased runoff and soil loss on unbound forest roads and machine operating trails, which in turn can impede the technical trafficability of machines and cause negative impacts on the environment. The aim of this study was to evaluate the effectiveness of three Best Management Practice (BMP) treatments used to control erosion occurring on machine operating trails. The treatments included water bar, water bar and hardwood brush (H-brush), and water bar and softwood brush (S-brush). For a more comprehensive assessment of both brush treatments, two levels of brush thickness were tested; 0.5 m and 1.0 m. Results indicate that the most effective BMP treatments were the water bar and softwood brush followed by the water bar and hardwood brush and finally the least effective was the water bar. The average runoff rates and soil loss from the machine operating trails with the water bar treatment (52.64 l per plot, 8.49 g m-2) were higher than runoff and soil loss at the trails protected with hardwood brush (23.75 l per plot, 4.5 g m-2), and the trails protected by the hardwood brush had higher runoff and soil loss compared to trails covered by softwood brush (15.83 l per plot, 2.98 g m-2). Furthermore, results of this study showed that regardless of the treatment, the amount of runoff and soil loss decreased consistently as the thickness of the brush mat increased. Overall, erosion control techniques similar to either H-brush or S-brush that provide direct soil coverage should be used for erosion control, and final selection should be based on costs, availability of material, or landowner objectives.

Effects of Ground-Based Skidding on Soil Physical Properties in Skid Trail Switchbacks

volume: 40, issue:

Effective skid-trail design requires a solid understanding of vehicle-soil interactions, yet virtually no data exist on the effects of harvest traffic on soils in the switchback curves common in mountainous terrain. We contrast for the first time the effect of skidding on dry bulk density, total porosity, macroporosity, and microporosity in the straight segments of the skid trail and in various positions within switchbacks of differing trail curvature (deflection angle) on different slope gradients. Treatment plots with three replications included combinations of two classes of curvature (narrow = high deflection angle, 60–70°; wide = low deflection angle, 110–130°) and two categories of slope gradient (gentle = ≤20%; steep = >20%). The Cambisol soil was sampled in control and trafficked areas both before and after three passes with a rubber-tired skidder. After only three passes, significant effects were seen for dry soil bulk density (+), total porosity (–), macroporosity (–), and microporosity (+), with steady trends from undisturbed controls to straight segments to wide curves to narrow curves. Soil damage increased gradually and consistently toward the apex of the curve, particularly in narrow curves on gentle slopes. Our results establish that curvature and switchback position are important factors affecting soil compaction in ground skidding. The strong observed effects of even low harvest traffic volume on soil physical properties in curves indicate that the degree of soil compaction in skid trails may be underestimated in areas with numerous switchbacks, the placement of which within a skid trail system may require careful consideration on mountainous terrain.

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Web of Science Impact factor (2018): 2.258
Five-years impact factor: 2.197

Quartile: Q1 - Forestry

Subject area

Agricultural and Biological Sciences

Category/Quartile

Forestry/Q1