Volume 45 No.1
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Volume 45 No.1

Infrastructure Requirements for Clear-Fell Harvesting of Small-Scale Plantation Forests in New Zealand

volume: 45, issue:

Background: Small-scale forests (woodlots) increasingly account for a greater proportion of the total annual harvest in New Zealand. There is limited information on the extent of infrastructure required to harvest a woodlot; road density (trafficable with log trucks), landing size, or the average harvest area that each landing typically services.

Methods: This study quantified woodlot infrastructure averages and evaluated influencing factors. Using publicly available aerial imagery, roads and landings were mapped for a sample of 96 woodlots distributed across the country. Factors such as total harvest area, average terrain slope, length/width ratio, boundary complexity and extraction method were recorded and investigated for correlations.

Results: The average road density was 25 m/ha, landing size was 3000 m2 and each landing was serviced on average 12.8 ha. Notably, 15 of the 96 woodlots had no internal infrastructure, with the harvest completed using roads and landings located outside of the woodlot boundary. Factors influencing road density were woodlot length/width ratio, average terrain slope and boundary complexity. Landing size was influenced by average terrain slope, woodlot length/width ratio, and woodlot area.

Conclusion: The results provide a contemporary benchmark of the current infrastructure requirements when harvesting a small-scale forests in New Zealand. These may be used at a high level to infer the total annual infrastructure investment in New Zealand’s woodlot estate and also project infrastructure requirements over the foreseeable future.

Effects of Boom-Tip Control and a Rotating Cabin on Loading Efficiency of a Forwarder: A Pilot Study

volume: 45, issue:

Climate change and associated heat waves and droughts are causing enormous amounts of damaged wood in Central Europe. To face these challenges, mechanized timber harvesting systems consisting of single-grip-harvesters and forwarders are commonly employed due to their high productivity and work safety. Despite the advantages of these work systems, the operation of advanced forestry machines requires lengthy training and entails high levels of mental strain for machine operators. In recent years, operator assistance systems have been installed in forest machines with the intention of reducing mental workload of machine operators, thereby improving productivity. However, knowledge of the actual effect of operator assistance systems on productivity is still lacking.

The present case study surveyed the effect of two recently released operator assitance features, Intelligent Boom Control (»IBC«) and a rotating cabin (»RC«), on productivity during loading cycles, by means of a time study. Therefore, IBC and RC were tested in different loading settings using a forwarder, John Deere 1210G. Three loading angles were tested (55°, 90° and 125° azimuthal and counterclockwise to the machine axis) in combination with five loading distances (4 m, 5.5 m, 7 m, 8.5 m, and 10 m distance from the crane pillar). The 15 loading positions were sampled using four variants (I: IBC off RC off, II: RC on IBC off, III: IBC on RC off, IV: IBC on RC on), capturing 10 replications for each position and variant, resulting in 600 loading cycles in total.

When the operator was not supported by any system, mean time consumption per loading cycle amounted to 20.6 ± 0.114 sec. The utilization of IBC resulted in a significant reduction in time consumption of 2 seconds per loading cycle. Moreover, further time savings were observed when IBC was engaged in combination with a rotating cabin, leading to a mean time consumption of 17.8 ± 0.114 sec (or 14% improvement) per loading cycle. Although the lowest time consumption was observed when IBC and RC were engaged, the use of RC alone did not show any significant time improvements.

Since loading activities occupy approximately 50% of the total cycle time in timber forwarding, potential time savings within this work element are crucial for further improvements of work productivity. This pilot case study quantified the time savings when IBC and RC were engaged during loading in an experimental setting. The results can be used as a basis for further investigations dealing with factors influencing the productivity of highly mechanized timber harvesting systems.

Overview of Global Long-Distance Road Transportation of Industrial Roundwood

volume: 45, issue:

The aim of the study was to provide a comprehensive overview of global long-distance road transportation of industrial roundwood. The study focused on the maximum gross vehicle weight (GVW) limits allowed with different timber truck configurations, typical payloads in timber trucking, the road transportation share of the total industrial roundwood long-distance transportation volume, and the average long-distance transportation distances and costs of industrial roundwood. The study was carried out as a questionnaire survey. The questionnaire was sent to timber transportation logistics experts and research scientists in the 30 countries with the largest industrial roundwood removals in Europe, as well as selected major forestry countries in the world (Argentina, Australia, Brazil, Canada, Chile, China, Japan, New Zealand, South Africa, Türkiye, the United States of America and Uruguay) in February 2022, and closed in May 2022. A total of 31 countries took part in the survey. The survey illustrated that timber trucking was the main long-distance transportation method of industrial roundwood in almost every country surveyed. Road transportation averaged 89% of the total industrial roundwood long-distance transportation volume. Timber truck configurations of 4 to 9 axles with GVW limits of around 30 tonnes to over 70 tonnes were most commonly used. The results indicated that higher GVW limits allowed significantly higher payloads in timber trucking, with the lowest payloads at less than 25 tonnes, and the highest payloads more than 45 tonnes. The average road transportation distance with industrial roundwood was 128 km, and the average long-distance transportation cost in timber trucking was €11.1 per tonne of timber transported. In the entire survey material, there was a direct relationship between transportation distance and transportation costs and an inverse relationship between maximum GVW limits and transportation costs. Consequently, in order to reduce transportation costs, it is essential to maximise payloads (within legal limits) and minimise haul distances. Several measures to increase cost- and energy-efficiency, and to reduce greenhouse gas emissions in road transportation logistics, are discussed in the paper. On the basis of the survey, it is recommended that up-to-date statistical data and novel research studies on the long-distance transportation of industrial roundwood be conducted in some countries in the future.

Development and Evaluation of a Felling Head for a Light Forest Crawler

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With motor-manual wood harvesting (by a forest worker with a chainsaw) fatal accidents happen every year when the tree is felled or when parts of the crown fall down. The alternative is to fell trees mechanically using a timber harvester head, which, however, must be brought up to the trees in the forest by means of its crane. With the usual crane reach of 10 m, the harvester needs a system of parallel strip roads with a spacing of 20 m. Furthermore, the harvester needs a dead weight of around 20 tons that compacts the soil. Both consequences increasingly evoke critics. The requirement to fell trees mechanically and to enlarge the distance between the strip roads calls for a solution to fell trees with a small, light machine that can apply its felling tool to the tree in close proximity. Together Pfanzelt Maschinenbau GmbH and the Professorship for Forest Technology of Technische Universität Dresden have run a project for developing a compact, new type of felling head, which is attached to the existing forest crawler »Moritz FR70/75« by means of a short manipulation arm. This head imitates the felling technique, which is applied by a forest worker, in a mechanical way with a high grade of automatization. Even though this machine works with higher system costs, it is significantly faster and more precise than the motor-manual version. The functional principle of the felling head was developed, patented, conceptualized and optimized with the help of prototypes and individual tests at the TU Dresden, Professorship for Forest Technology. After that, it was completely designed, manufactured and automated in terms of control technology by the Pfanzelt company. More than 100 conifers with a felling diameter of up to 50 cm were felled safely and without any problems with the prototype. The possible integration into harvesting processes as well as the effects on the use in the forest stands were analyzed in detail. The project has shown that it is possible to fell trees in a fully mechanized way without danger for the forest worker with a machine that weights roughly a tenth of the dead weight of a conventional harvester.

Effect of Prior Tree Marking on Cutting Productivity and Harvesting Quality

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Prior tree marking is used to guide loggers or forest machine operators on which trees to cut to achieve the desirable silvicultural quality of a thinning treatment. In the future, this beneficial but expensive human work could be automated with advanced driver assistance systems. This study aimed to investigate the effect of conventional prior tree marking on cutting productivity and harvesting quality of the first and later thinnings. A comparative time study was conducted with four experienced harvester operators. The operators thinned 4825 stems with the cut-to-length (CTL) harvesting method in eight thinning stands. The time consumption of the different time elements of cutting work was measured to model the cutting productivity with average values or regress these values against the stem volume or density of removal. Prior tree marking increased the cutting productivity by an average of 2.8% in the first thinnings and 2.7% in later thinnings by reducing the time consumption of boom-out (positioning the harvester head for cut) and moving. The operator effect was notable, even though only experienced operators participated in the study. For some operators, prior tree marking did not make cutting work more efficient, and sometimes hampered it. Prior tree marking improved the quality of the remaining stands in thinnings by producing a more accurate density of remaining trees after the harvesting operation in relation to thinning guidelines. When the stands were not marked, the operators chose trees of poor quality with almost the same accuracy as the forester. These findings lay the foundation for the next-generation operators’ guidance and decision support systems, which could detect trees around the harvester and guide the operator in tree selection and managing better thinning intensity in cutting work. Although prior tree marking increased productivity only marginally, the improvement in the quality of harvesting operations must be acknowledged.

Using Cyclic CBR Method to Determine Resilient Modulus of Hydraulic Binder Stabilised Road Pavement Base Layers

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The mechanistic-empirical (E-M) design of pavement structures requires knowledge of the elastic modulus of the layers comprising the structure. The necessary cyclic (dynamic) triaxial testing is expensive and cumbersome for low-volume forest and agricultural roads. Opiyo (1995) developed a method called cyclic CBR (cCBR) to determine the resilient modulus (Mr) of granular road construction materials using CBR testing equipment. The present study tested the cCBR method on silty, fine sand stabilised with lime and a lime-cement mixture. For the test, 24 test specimens were prepared by adding 3, 5 and 7% pure lime and a 70–30 lime-cement mixture at the targeted 8–23% water content. Three metrics were used to express the bearing capacity of the specimens: (1) the commonly used CBR% value, (2) the Mr value calculated as a function of load force and elastic deformation determined as a result of the cCBR test, and (3) the resilient modulus calculated from the CBR value. The experimental results showed that the initial water content had a greater effect on the bearing capacity than the binder dosage. The present study found the cCBR procedure to be feasible. The test results were converted to a resilient modulus value using the formula developed by Opiyo and Molenaar, respectively. The calculated resilient modulus values from the CBR value exhibited a wide variation. Uzan’s formula provided similar results to those calculated by Molenaar’s formula. A 250 m long experimental road section was also constructed to verify the laboratory data. Based on the laboratory tests, five different 50 m long stabilisation layers were built. The bearing capacity data measured with the handheld BC-1 LFWD and KUAB-FWD equipment verified Molenaar’s formula.

Economic Evaluation and Performance of a Tree Planting Machine Performing in Two Different Slope Classes and Conditions of Harvesting Slash

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In recent years, fully mechanized planters have gained attention in Brazil on flat to steep terrain. A field study was conducted to analyze the potential of a planting machine composed of a hydraulic crawler excavator and a planter unit to perform soil preparation and planting in two slope classes and two conditions of slash presence. The experimental area was divided according to slope – undulating (8% to 20%) and strong undulating (20% to 45%) – and the presence of slash. Slope class did not significantly affect productivity, nor was there a significant interaction effect between the slope and slash factors. The presence of slash proved to be statistically different, with mean productivity of 236 seedlings hour-1 when reloading the carousel in an area without harvesting slash. Tree planting machine utilization was 75.13%, and the mechanical availability was 79.6%. The presence of slash significantly reduced the tree planting machine productivity, including the seedling reloading time, suggesting a newer research line for fasters reloading seedling systems.

Shortage of Labour Force in Forestry of Bosnia and Herzegovina – Forestry Experts' Opinions on Recruiting and Retaining Forestry Workers

volume: 45, issue:

Labour force represents the sum of human physical and mental abilities used for the production of whatever kind of use values. In forestry, the performance of work operations, especially wood harvesting, represents a high-risk, physically intensive, and professionally very demanding activity, which inevitably requires a qualified and sustainable labour force. Professional, skilful and motivated forestry workers are the basic requirement for efficient forestry operations and make a constituent part of todays sustainable forest management. However, the forestry sector has recently been facing the increasing problem of a shortage of forestry workers i.e. the major challenge of obtaining the necessary labour force. The reasons for this are different demographic, economic, technological and political processes, as well as the specifics of the forestry sector itself. Therefore, in addition to some general indicators of the forestry workforce condition in Europe and worldwide, this paper presents forestry experts’ reflections on the future perspectives of forest work in Bosnia and Herzegovina. Special attention is paid to current issues and problems in attaining and ensuring the necessary labour force (attitudes on forestry work and the profession of forestry worker, gravity of the labour shortage, leading causes and reasons for the lack of forestry workers) and to possible measures and instruments important for improving the forestry workforce sustainability (factors for successful recruitment of forestry workers, stronger retention of workers, greater work commitment, general forest management issues affecting workforce sustainability, etc.). The opinions of forestry experts in public and private companies were statistically tested for differences. The aim of the study is to sensibilize the sector and the public on the problems of the labour force in forestry, its condition and status, and to create the basis that can contribute to bettering the status and sustainability of the labour force in forestry.

Accuracy of Photo-Optical Timber Measurement Using a Stereo Camera Technology

volume: 45, issue:

Harvested timber requires efficient and accurate measurements for timber trade. Recently, the amount of timber that is harvested for industrial purposes is growing and methods for roundwood measurements are under constant development. Some of these solutions are with certification confirming its accuracy, some of them are proposed for general use without certification. The aim of this paper was to select the best and most useful electronic solution for timber volume masurement and calculation, and to recommend the most effective and accurate solution for future timber trade. Three photo-optical systems were tested: LogStackPro, iFovea and Timbeter. Each system was used to measure 71 stacks of pine and oak roundwood, which amounted to 3481.15 cubic meter stacked. Timber volumes obtained from the manual measurements were used as reference. Volumes obtained from the photo-optical systems were larger in comparison with the volume from manual measurements, by 3.37, 8.07 and 9.08%, in LogStackPro, iFovea and Timbeter, respectively. It was concluded from the tested systems that, currently, the most recommended solution for timber measurement will be LogStack Pro, which also presented, in most cases, the smallest deviations from the volume obtained in manual measurements.

Assessing Forest Traversability for Autonomous Mobile Systems Using Close-Range Airborne Laser Scanning

volume: 45, issue:

Advances in sensor technology and computing performance has brought us into an era of digital forestry where a forest environment can be digitally replicated. At the same time, an increasing interest in the use of unmanned vehicles and other autonomous mobile systems (AMSs) in forest mapping and operations has emerged. However, a forest is an unstructured and rather complex environment for AMSs to operate in, and usually some kind of a priori information of traversability is required. The aim of this study was to assess forest traversability for AMSs using high-density airborne laser scanning (ALS) point clouds. It was assumed that such point clouds acquired from a helicopter flying at a low altitude can be used to characterise vegetation obstacles affecting forest traversability. A voxel-based vegetation occupancy analysis was carried out with the aim to detect open space to define traversable three-dimensional space. The experimental setup included seven sample plots (32×32 m) representing diverse boreal forest structures. Terrestrial laser scanning (TLS) was used for obtaining reference for vegetation occupancy. Comparison between ALS and TLS revealed an overall accuracy of 0.85–0.94 with a recall of 0.78–0.91 and a precision of 0.62–0.74 for ALS-based voxel classification for vegetation occupancy depending on forest structure. This implies that up to 91% of voxels assigned a classification »occupied« based on the TLS could be correctly classified using the ALS, while up to 74% of voxels assigned a classification »occupied« using the ALS were occupied based on the TLS. Density of low vegetation accounted for 83% of the variation in accuracy and precision. The feasibility of vegetation occupancy information to be used by an AMS for navigation was also demonstrated. It was assumed that the ALS data convey as sufficient information of AMS path planning as does the TLS data. The experiments showed that out of 1393 randomly generated paths based on empty space detected by the ALS, 72% were considered feasible when validated with the TLS data. The success rate in path planning varied from 0.54 to 0.92 between the sample plots and was seemingly affected by vegetation density that accounted for 53% of variation in success rate. Altogether, the demonstrated possibility to predefine forest traversability using remote sensing will support the use of AMSs in forestry.

Development of a Sustainable Maintenance Strategy for Forest Road Wearing Courses in Different Climate Zones

volume: 45, issue:

This study was done to determine the appropriate maintenance strategies for the deteriorating gravel forest roads in the Mediterranean, sub-humid and semi-arid climates. Unmanned Aerial Vehicle (UAV) was used to monitor Unpaved Road Condition Index (UPCI), immediately after maintenance activities and seasonally in one year. The deterioration time of the wearing course was predicted using Markov chain analysis. Results showed that roads in sub-humid climates presented lower UPCI (7.19) compared to the Mediterranean (7.81) and semi-arid (8.82) climates. When roads were maintained by a high-budget strategy, deterioration time was longer than when other strategies were used. The cost-effectiveness (CE) value of the low-budget strategy was more favorable than different strategies in all traffic levels of the Mediterranean climate and high-traffic roads in a semi-arid environment. Low-budget maintenance activities include one culvert improvement per 6 km, light blading, and 30 mm layer graveling. In a semi-arid climate, a medium-budget maintenance strategy was more efficient in medium and low-traffic roads. Medium, high, and low-budget maintenance strategies were efficient in high, medium, and low-traffic roads in sub-humid climates. High-budget maintenance activities include one culvert improvement per 4 km, heavy blading and local compaction, and 60 mm layer graveling. Overall, it was concluded that monitoring UPCI over time and probability analysis using time series is helpful for a sustainable and long-term management of forest roads.

Soil Characteristics in Oak Lowland Stand – A Case Study of a 6-Wheeled Forwarder's Impact on Forest Soil

volume: 45, issue:

The behavior of the vehicle-soil interaction and reduction of the possible soil damage to an acceptable level is one of the goals of forest engineering. This study aimed to analyze the impact of a 6-wheeled forwarder on water-physical soil characteristics on lowland soil – pseudogley. The research was conducted using a 17-ton Timberjack 1710B forwarder, which forwarded 694.1 m3 volume of oak (Quercus robur L.) assortments. Soil characteristics were measured after each of the eight passes of the loaded forwarder. Bulk density measured on the surface layer ranged from 1.01–1.23 (Me=1.10) g/cm3 (undisturbed soil); 1.14–1.70 g/cm3 (multiple passes of the loaded forwarder). The highest soil density increase was observed after the first pass of the loaded forwarder (16%). Soil solid phase ranged from 2.49 to 2.73 g/cm3 with no statistically significant difference between undisturbed soil and soil after multiple passes of the vehicle. The highest porosity decrease was observed after the first pass of the loaded forwarder (10%). The highest soil water retention capacity decrease was observed after the first pass of the loaded forwarder (3%). The highest soil air capacity decrease was observed after the first pass of the loaded forwarder (30%) compared to the undisturbed soil of the forest stand.

Assessment of Tractor Tires Used in Forest Conditions in Terms of Traction Performance and Impact on Ground

volume: 45, issue:

This paper presents the assessment of selected tractor tires used in forest conditions. The first element of this assessment is related to tractive properties, while the second part concerns the potential negative impact of the tires on the ground. The research was conducted on the skid trail located in a lowland pine stand in Poland (Lower Silesian District). The 9.5-24, 400/55-22.5 and 11.2R24 tires were used for the experiment, and the following tractive parameters were analyzed: traction force, pulling force and rolling resistance. These parameters were determined during the experiment using special measure stand mounted on a 3-point linkage of the tractor. In addition to the traction properties, the impact of the wheel on the ground was determined – this evaluation included measurements of footprint areas and calculation of contact pressures. Based on the obtained results, it was shown that the increase of the vertical load and reduction of the inflation pressure of tires can cause an increase in net traction force of as much as 35% and 16%, respectively. The analysis of contact areas and pressures showed that the widest tire (400/55-22.5) had the least negative impact on the ground. The reducing of inflation pressure allowed to obtain higher traction force, higher contact area and smaller contact pressures.

Effects of Boom-Corridor and Selective Thinnings on Harvester Productivity in Dense Small Diameter Pyrenean Oak (Quercus pyrenaica Willd.) Coppices in Spain

volume: 45, issue:

Due to socioeconomic transformations in the 20th century, Quercus pyrenaica Willd. coppices in Spain, as well as other European coppices, have experimented an abandonment and lack of intervention leading to stagnant high density stands with fragile health due to competition. Thinnings are often required to ensure their stability and health, producing forest products such as firewood or biomass, which are key energy sources in a carbon-neutral economy. However, thinnings are seldom performed because they lack economic sustainability due to a low productivity, high costs and low biomass prices. In this study, two thinning methods, selective thinning (ST) and boom-corridor thinning (BCT), were tested carrying out a time study in a high-density small-diameter Q. pyrenaica stand in the León province (Castilla y León, Spain) with a forest harvester base machine, on which an accumulating felling head Bracke C16c was mounted. The residual stands were significantly different regarding the final density (greater in BCT) and the final average DBH (bigger in ST), while thinning intensity (odt·ha-1) was the same. In most work elements, time per tree was not significantly different. BCT showed a significant 48.6% increase in harvester productivity when compared to ST, with averaging 4.43 and 2.99 odt·pmh-1, respectively, due mainly to the average weight per extracted tree, 42% greater in BCT. When considering the common range of unit tree weight, the productivity was 16–23% greater for BCT, far less than observed in the trials. These results show the potential of BCT over ST in the studied conditions, although there is room for improvement. Further studies could include the future evolution of the treated stands and perform a cost analysis.

Comparing Different Replacement Policies for Logging Machines in Brazil

volume: 45, issue:

A dynamic programing algorithm to identify schedules that minimize the discounted cost (DC) of logging machines over a planning horizon including gains from technological progress was used. The identified schedules were also compared with three alternative replacement policies derived from the literature and Brazilian forestry companies. The case study used a harvester and a forwarder and a 100-year planning horizon, where the maximum replacement limit was 8 years. To apply the dynamic programing algorithm, it was necessary to generate lists from cash flows, which incorporated the possible replacement combinations of a series of machines according to the length of the planning horizon and the maximum replacement limit. The lists were formed by three descriptors: predecessor node (moment of purchase of the machine), future node (point of sale for the acquisition of a new machine), and arc value (DC information, the mean production cost and mean production). The results show that the DC identified for the series of harvester replacements was higher compared to the forwarder. It was also identified that the harvester's economic life is shorter, and with technological progress, there was a reduction in the economic life of both machines. Technological progress was also responsible for reducing the average production cost and increasing the average production of machines. When comparing the alternative schedules (AS), it was found that, although AS had a higher DC value and mean production costs, there was very little difference between them. In the harvester's case, AS01 had the highest DC value ($4.36 million). By choosing it, the decision maker would bear a DC boost of $54,000, while AS02 and AS03 would trigger an increase of $43,000 and $32,000, respectively. For the forwarder, the schedule with the highest DC value was AS03 ($3.69 million). The postponement of the replacements made in alternative schedule 01 and alternative schedule 02 resulted in an increase in the DC of $5000, while the anticipation of the replacements made in the alternative schedule 03 resulted in an increase of $48,000. The aspect that stood out the most, in relation to the results presented, was the small variation that the alternative schedules presented in relation to the schedules obtained using the dynamic programing algorithm. With a DC variation of less than 1.4%, the results lead us to conclude that the decision maker will not suffer much harm in choosing any of the alternative schedules tested.

Incorporating Simulators into a Training Curriculum for Forestry Equipment Operators: A Literature Review

volume: 45, issue:

Forestry equipment simulators offer opportunities for new operators to become familiar with operating logging machines as well as a promising solution to the high costs of training forestry equipment operators. Current literature lacks a synthesis on how best to train forestry equipment operators using simulators. The goal of this review was to identify effective ways to incorporate forestry equipment simulators into an equipment operator training curriculum. We analyzed a total of 14 independent studies in which construction and forestry equipment operators were trained on simulators and engaged in discussions with nine professionals in the field of heavy equipment operator training. In this review, traditional machine training and simulator training practices are introduced. Then, four key aspects of skill acquisition for forestry equipment operators are identified. Information collected from peer-reviewed literature and discussions with industry experts are used to consider how each aspect of skill acquisition is addressed in both traditional training using real machines and simulator-based training. Drawing on these sources, benefits and drawbacks of traditional machine training and simulator-based training for forestry equipment operators are synthesized and discussed. Finally, a model for an integrated and adaptive training curriculum that incorporates principles and technologies from both traditional machine training and simulator training is presented.


Web of Science Impact factor (2022): 3.200
Five-years impact factor: 3.000

Quartile: Q1 - Forestry

Subject area

Agricultural and Biological Sciences