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.
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.
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.
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%.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
volume: 41, issue: 1
Logging firms are a critical link in wood supply chains, connecting forest landowners with markets for wood products. Improving operational planning can benefit individual logging firms as well as the larger wood supply chain in which they operate. Applying concepts from Theory of Constraints (TOC) to timber harvesting may help achieve greater predictability and efficiency when planning harvest operations. However, examples that demonstrate how TOC can improve logging operations are lacking. This study focuses on the analysis of production and activity data collected during the harvest of a temperate mixed hardwood forest in the Northeast United States using a chainsaw-forwarder system through a TOC lens. Specifically, the drum-buffer-rope (DBR) method was used to reschedule operator and machine activities such that a consistent flow of wood from stump to landing was maintained despite anticipated production setbacks. The results of this case study provide insights into the usefulness of applying TOC to logging operations. In particular, logging businesses must be able to estimate machine and operator productivity within a given harvest context to identify and exploit system constraints, while taking full advantage of unused capacity of any non-constraint functions
volume: 41, issue: 1
According to National Forest Inventory data, there is an urgent need for tending seedling stands of at least 700,000 ha and a need for 1 million ha in the next few years in Finland. The motivation for forest owners to conduct pre-commercial silvicultural operations is low due to the associated high costs. Especially the costs of tending and clearing operations after the regeneration of the stand have been increasing. In addition, the availability of labor is a restricting factor due to the high seasonality of silvicultural works.
In the 2000s, several solutions for the mechanization of tending have been proposed. These are based on the use of harvester or a forwarder as a base machine. Typically, light weight base machines are favored to reduce the hourly cost of operations and the impacts on the remaining seedlings. There have been challenges with the high speed of the cutting device, which increases the risk of damages to the head and the ignition of forest fires when the circular saw or chain hits stones, for example. In addition, the chain can become dislocated due to bending forces caused by stumps.
Cutlink has presented a low RPM solution based on rotating cone-shaped shears that cut 50–100 cm wide corridors between and around seedlings. In this study, the productivity of mechanized tending with Cutlink´s device compared to manual tending was evaluated in spruce seedling stands in central Finland. The productivity, fuel consumption and quality of the seedling stand after the operation were measured. In early tending, the productivity of motor manual tending was notably better than when using the Cutlink device. Crucial factors for the competitiveness of a mechanized alternative include the annual working hours and finding suitable working areas for the machine. Additional work for the device and base machine can also be found in the clearing of forest road sides
volume: 41, issue: 1
The analysis evaluates the potential and methods of the respective assessment of beech trees, beech logs and sawn timber. The objective of the study was to assess the impact of the quality of the incoming raw material (tree) on the quality and quantity of products – obtained at the sawmill. The study presents a model that indicates the relations between the assessment of the quality of a standing beech tree and the quality of the sawmill products obtained from its wood. In addition, relations between individual quality classes of sawlogs, pulpwood, energy wood and sawn timber are shown. Standing trees were assessed in three sites according to the national 5-grade quality scale, assortments produced from selected trees pursuant to the EN 1316-1 standard, and sawn timber produced from assortments according to the rules of the European Organisation of the Sawmill Industry (EOS). In total, 87.04 m3 of timber was harvested. In higher quality trees (quality 1 and 2), the shares of sawlogs were between 53% and 72% of gross tree volume, but in the poorest quality trees, the shares were only between 23% and 36%. What remained was pulp and energy wood. In trees of excellent quality (quality 1), sawlogs of the highest quality prevailed (A and B quality grade), while sawlogs of C and B quality prevailed in trees of lower quality. Covered knots and heart defects were typically the decisive criteria for classifying sawlogs quality in all three sites. A total of 30,786 m3 of unedged timber was sawn from the sawlogs, which comprised 35% of the total gross quantity of trees on average. Nine percent of the sawn timber was classified into the A–EOS class (top quality), 27% into the B–EOS class and 47% into the C–EOS class. Seventeen percent of the timber was only suitable for post-processing. The crucial criteria for classifying sawn timber were as follows: dead and rotten knots, heart, curvature and cracks. Above-average sawlogs (A and B quality grade) was mainly obtained from trees of better quality. Relations between the quality of trees, sawlogs and sawn timber indicated the suitability of classifying standing trees and sawlogs, since it was possible to produce sawn timber of higher quality from quality trees or logs. The model presents a rare attempt to establish and monitor quality and quantity from standing tree to end product.
volume: 41, issue: 1
Wood-harvesting activities are conducted by contractors through tendering based on prices determined by the amount of transported wood, land conditions and transport method parameters. Managers should determine the average completion time of the work and the base price accurately to prevent both work and contractor losses prior to the tender and note the same in the tender contract. Thus, prediction of productivity in wood production is of great importance in the determination of the work duration and cost. In this context, the aim of the present study was to determine the most accurate estimation model that would predict productivity (Pe) based on log volume (Vt), route slope (P) and winching distance (D) in uphill cable skidding activities with a drum tractor. In the current study, estimation models were developed that use both linear regression through SPSS employing all data and the robust regression method that minimizes the effect of outliers. Harvesting units were selected among pure spruce (Picea orientalis (L.) Link) stands via the uphill cable-skidding method with a tractor in the North-East of Turkey. Route slope, winching distance, log volume and time-consumption data were collected in the chosen harvesting units and productivity prediction models were developed with these data. In this study, the productivity estimation was performed using linear regression in SPSS and robust regression methods prepared in MATLAB environment. The coefficients calculated by these methods were statistically tested, and it was determined that the winching distance coefficient was insignificant with both methods. Thus, the productivity estimation model was re-determined with both methods based on the slope and log volume parameters, and the findings were compared. Additionally, the standard errors of the coefficients of both models were compared and it was concluded that the robust method was more sensitive than the SPSS regression method.
volume: issue, issue:
Ground-based skidding operations can lead to soil compaction and displacement, which could cause negative effects on forest soil. Hence, some efforts such as forestry best management practices (BMPs) must be implemented in the prone area to mitigate these possible impacts. Several materials and treatments have been adopted to suppress these adverse effects by increasing the ground cover. However, the effects of mulch treatments on runoff and sediment yield are inconclusive with a diverse range of effectiveness. For these reasons, in this research mulch treatments were tested as to determine how the application of organic mulch amendments such as straw and leaf litter and contour-felled logs would alleviate the runoff and sediment yield on machine operating trails and ensure successful hillslope stabilization. The aims of the study were to analyse and compare the effectiveness of leaf litter (LM) and straw mulch (SM) rate and different distances of contour-felled logs (CFL) to mitigate the runoff and sediment yield, and examine the impact of rainfall intensity on effectiveness of litter mulch, straw mulch, and contour-felled logs. Totally, 30 bounded runoff plots in the machine operating trails and four treatments including litter mulch (LMR1: 0.62, LMR2: 1.24, and LMR3: 1.86 kg m-2), straw mulch (SMR1: 0.45, SMR2: 0.92, and SMR3: 1.34 kg m-2), contour-felled logs (CFL10: 10, CFL20: 20, and CFL30: 30 m), and untreated area were established in triplicate with 4 m width and 100 m length. During the study period, the runoff and sediment yield in the untreated trails (U) were 2.36 mm and 11.84 g m-2. Straw (from 41.5 to 60.6%) and litter mulch (from 38.1 to 55.1%), and contour-felled logs treatments (from 70.8 to 88.1%) significantly decreased the runoff, compared to U treatment. Results show that mulch treatments with three different levels of Litter Mulch Rate, LMR1, LMR2, and LMR3 decreased mean sediment by 46.6, 64.0 and 71.8%, in the treatments with three different levels of Straw Mulch Rate, SMR1, SMR2, and SMR3 decreased mean sediment by 42.9, 62.1, and 69.9%, and in the treatments with three different distances of Contour-Felled Logs, CFL10, CFL20, and CFL30 decreased mean sediment by 90.6, 94.7 and 88.3% comparing to U, respectively. The relationships of the runoff and sediment responses to increasing mulching rate of litter and straw followed as negative logarithmic curves, but the decreasing-increasing trends were observed in runoff and sediment yield as the distance between contour-felled logs increased from 10 to 30 m. Polynomial regression equations were developed for predicting the runoff and sediment yield as a function of the application rate of litter and straw mulch and the distance between contour-felled logs, and rainfall intensity. We concluded that contour-felled logs treatment was more effective than both litter and straw mulch to mitigate the runoff, runoff coefficient, and sediment yield on machine operating trails. As a management measure, it could be possible to propose that the contour-felled logs with a distance of 20 m be prescribed to protect the machine operating trails from the negative effects of surface waterflow.
volume: issue, issue:
The processing of Eucalyptus logs is a stage that follows the full tree system in mechanized forest harvesting, commonly performed by grapple saw. Therefore, this activity presents some associated uncertainties, especially regarding technical and silvicultural factors that can affect productivity and production costs. To get around this problem, Monte Carlo simulation can be applied, or rather a technique that allows to measure the probabilities of values from factors that are under conditions of uncertainties, to which probability distributions are attributed. The objective of this study was to apply the Monte Carlo method for determining the probabilistic technical-economical coefficients of log processing using two different grapple saw models. Field data were obtained from an area of forest planted with Eucalyptus, located in the State of São Paulo, Brazil. For the technical analysis, the time study protocol was applied by the method of continuous reading of the operational cycle elements, which resulted in production. As for the estimated cost of programmed hour, the applied methods were recommended by the Food and Agriculture Organization of the United Nations. The incorporation of the uncertainties was carried out by applying the Monte Carlo simulation method, by which 100,000 random values were generated. The results showed that the crane empty movement is the operational element that most impacts the total time for processing the logs; the variables that most influence the productivity are specific to each grapple saw model; the difference of USD 0.04 m3 in production costs was observed between processors with gripping area of 0.58 m2 and 0.85 m2. The Monte Carlo method proved to be an applicable tool for mechanized wood harvesting for presenting a range of probability of occurrences for the operational elements and for the production cost.
volume: issue, issue:
Accurate predictions in forest operations can be used towards effective planning, costing, and maximizing the productivity of machines in mechanised cut-to-length (CTL) harvesting. There is a general and substantial gap in forwarder productivity data available for pine sawtimber in South Africa at present, and as the number of product assortments being harvested increase there is a need for more work to quantify the effects of extracting products of different dimensions. The aim of this study was to calculate the time consumption and productivity of two models of Ponsse forwarders (15 t and 20 t capacity) to consider and compare the effects of multiple variables including machine capabilities, product assortment, load size, extraction distance and fuel consumption. Productivity averaged at 34.08 m3 per productive machine hour excluding delays longer than one minute (PMH1) for the smaller machine, and 55.94 m3/PMH1 for the larger machine. Productivity and average log volume were strongly positively correlated. Regression models were created for each machine where load volume and extraction distance were both significant factors for predicting productivity. Average fuel consumption of the smaller machine was 15.55 l/PMH1 and 0.47 l/m3, and 20.57 l/PMH1 and 0.43 l/m3 for the larger machine. The product with the largest volume was found to require the least fuel per m3. The models developed could aid in predicting system productivity and potentially carbon emissions under similar conditions in a South African context of industrial plantation forestry.
volume: issue, issue:
Demand for higher value-added wood products stimulates research for new, mainly mechanized, thinning operations in order to increase productivity and reduce production costs. In this context, the aim of this study was to evaluate the impact of distance between strip roads on forwarder productivity and costs of thinning operations in Pinus taeda stands. The study was carried out in 10-year-old Pinus taeda stands located in Parana State, Brazil. Two thinning methods were evaluated: (1) TH5: systematic harvest in every fifth tree row and selective harvest in adjacent rows; and (2) TH7: systematic harvest in every seventh tree row and selective harvest in adjacent rows. Working cycle times, productivity and costs were determined through a time-motion study of the forwarder. The additional variables evaluated were wood assortments (industrial wood and energy wood) and extraction distances (50, 100, 150 and 200 m), and mean values were compared between thinning methods using t tests for independent samples (α=0.05). Loading and unloading elements consumed the most time in the working cycle, with lower participation time in TH7 due to greater availability of logs along the strip roads (higher pile volumes), influencing total cycle time up to the mean distance of 150 m for both assortments. TH7 consequently showed 6% higher productivity, its energy yield was 5.3% lower and its production cost was 3.0% lower.