The utilization of forest residues as a woody biomass feedstock for the production of bioenergy and bioproducts requires processing (i.e., comminution) to meet feedstock specifications, such as moisture content and particle size. The objective of this study was to determine the effect of small diameter processed hardwood (SH) and small and large diameter processed softwood (SS and LS) stems had on the productivity and cost of a track mounted sawdust machine that produced sawdust. In addition, moisture content, particle size distribution, bulk density, and the effect of knife wear were evaluated. The sawdust machine's 298-kW engine was capable of comminuting all material types except the LH stems. The machine's productivity ranged between 18.3 and 26.7 bone-dry metric ton (BDmT)/productive machine hour (PMH) at a cost of US $5.3 and US $3.6/BDmT, respectively. The moisture content of material used in the study ranged between 26 and 36%. The geometric mean particle lengths for SH, SS, and LS were 4.7, 5.3, and 4.4 mm, respectively. The machine could not process LH materials due to limited power. The bulk density of feedstock produced ranged between 234 and 281 kg/m3. Analysis indicated that knife wear did not have a significant effect on comminution productivity and feedstock quality while comminuting 60 green metric tons (GmT) of forest residues. The results from this study suggest that this sawdust machine can be useful in producing feedstock for new biomass conversion technologies that require small, uniform particles.
Thinning is a silvicultural process in which trees are both harvested selectively and systematically removed from a stand to enhance forest management and ecosystem dynamics. However, this practice is challenged by the mechanical damage to residual trees, and the nature of this damage, particularly on stand damage during mechanized row-thinning and manual selective thinning, in South Korea is unknown. Therefore, objectives of this study were to compare stand damage levels and wound characteristics between three different thinning operations: manual selective, manual row-, and mechanized row-thinning. After thinning, 12%, 15%, and 10% of the residual damaged trees were observed in manual selective, manual row-, and mechanized row-thinning, respectively. Both types of row-thinning predominantly demonstrated damages at the stem and butt region, whereas in manual selective thinning, the most of the damages occurred on the roots. Manual selective thinning exhibited a slightly larger average wound size (207 cm2) compared to mechanized row- (181 cm2) and manual row-thinning (165 cm2). The wound sizes on the stem in mechanized row-thinning were significantly higher than manual selective (p < 0.05). These results may be helpful in understanding exposure to damage among different thinning types and in managing its occurrence in future practices.
No abstract is provided for this article.
The forestry industry poses a higher risk of occupational accidents than other sectors, and understanding the occurrence and characteristics of injuries and fatalities is crucial for improving the safety and health of workers and establishing future strategies. In South Korea, although occupational injuries have declined since 2010, the number of occupational accidents in forestry remains higher than that in other sectors. Occupational injuries and fatalities present considerable challenges, and thus, our objective was to analyze and compare forestry accidents between 2010 and 2020. The results indicate that the highest average number of injuries occurred among workers older than 51 years and those with less than 6 months of experience. Timber harvesting and silviculture are among the most dangerous operations in forestry. Based on the analyzed dataset, amputation and laceration injuries, as well as slip and trip injuries, were the most common, accounting for 29.2% and 22.3% of total annual occupational accidents, respectively. These results may be explained by the labor-intensive, steep terrain operations in forestry. Our findings represent an essential resource for improving worker safety and health.
Forests are well known to control soil erosion and severe flooding. In the Democratic People's Republic of Korea (North Korea), deforestation was estimated at 20% between 1997 and 2014. This decline was mainly reflective of improper land use practices on steep slopes. Intensive deforestation and inappropriate land management can lead to severe soil erosion. The objective of this study was to describe the regional soil erosion severity in North Korea using the Revised Universal Soil Loss Equation (RUSLE) model coupled with a GIS technique. This model is widely being used to assess the potential mean annual soil erosion under different rainfall, soil characteristics, slope, and land use conditions. The results showed that the average annual rate of soil loss was estimated to be 15.8 tonnes ha−1 yr−1. Regionally, Nampo city is the most vulnerable region to soil erosion (55.1 tonnes ha−1 yr−1), followed by Hwanghaebuk-do (30.5 tonnes ha−1 yr−1), due to rapid land development. Denuded lands, which are estimated at around 6.5% of the total area, are predicted to have contributed 192.1 million tonnes yr−1 to the country's soil erosion. Participatory agroforestry and reforestation were found to be practical solutions to reduce soil erosion, particularly on degraded landscapes, and improve people's farm-based livelihoods.
In ground-based harvesting, machine traffic can cause soil physical disturbances including excessive compaction, the displacement of the soil surface and topsoil, and rutting. These impacts can indirectly hamper seedling survival and tree growth because of reduced soil permeability and root growth. However, the extent of soil disturbance in mechanized row thinning by harvester and forwarder systems in South Korea is unclear. Therefore, our objectives were to determine the impacts of two types of harvesters, soil textures, and extraction methods on soil compaction and rutting in a Korean Pine stand. The results showed that the machine passes affected soil disturbances. The soil bulk density inside the tracks (at 0–10 and 10–20 cm soil depths) after harvester passes (wheeled vs. tracked) increased by 17 and 27% and 30 and 20%, respectively. The largest impact was recorded for the forwarding track and significant differences were observed between the track and reference locations. Furthermore, the rutting depth in the forwarding trails was significantly higher than in the harvester trails. Thus, the application of a brush mat on harvester and forwarder trails may reduce machine-induced soil compaction. These results provide useful information to help forest engineers and field managers design environmentally sound ground-based harvesting operations.
Forests in Korea are mainly located in steep mountainous areas, where small-shovel-based extraction technology is widely used, with the level of mechanization undoubtedly low due to financial limitations. On this steep terrain, a better approach may be to use cable yarders, which can offer high revenues through cable-based extraction. Therefore, improving the efficiency of cable yarding activities in good-quality timber forests is necessary. The main objectives of this study were to (1) evaluate the productivity and cost of a cable yarder operation for tree-length clearcut treatment of a Larix kaempferi (Lamb.) Carr. stand and (2) compare the productivity efficiency of two yarder (K301-4 and HAM300) types. The productivity rates of the K301-4 ranged from 10.2 to 12.5 m3/productive machine hours, with corresponding costs of US $12.6–15.4 /m3. The productivity of the HAM300 was 26% lower than that of the K301-4 for a 30% lower cycle log volume while yarding and a comparable lateral distance. This study provides insights to support production and management decisions in the forest supply chain associated with planning cable-yarding operations.
Simulator training offers a safe and cost-effective approach to providing new operators opportunities to become familiar with operating modern machinery. However, in Korea, the current programs are insufficient in training skilled operators capable of handling advanced forestry machinery. Consequently, these programs fall short of developing the required technical expertise, leading to difficulties in workforce employment. We compared the performance of simulator-trained participants with that of machine-trained participants by testing operators on real equipment and assessing their stress levels. Participants were categorized as those with and without excavator certificates. Within each category, participants were further divided into those receiving training via simulators or those who were trained using actual equipment. Although we detected no significant differences in the overall performance of simulator- and machine-trained participants, compared with real machine training, simulator training promoted better performance, lower levels of frustration, and a reduced mental workload due to the safer and more controlled virtual environment. These findings can be used to develop more effective training programs by incorporating simulator-based modules that enhance skill acquisition whilst reducing risks. They can also inform policy decisions to improve workforce training in industries dependent on the operation of advanced machinery, thereby ensuring that operators achieve higher levels of competence and safety.
Background: Winch-assisted harvesting is an alternative to traditional cable yarding on steep slopes, offering improved operational efficiency and fewer limitations. Knowledge on the effects of winch-assisted harvesting on soil disturbance are limited. This study aimed to assess the effects of winch-assisted and conventional tracked harvester operations on soil compaction and machine slippage in a clear-cut stand with sandy loam soil. Methods: We evaluated changes in soil physical properties, in depth and extent, along machine operating corridors with and without winch-assist across slope gradients ranging from 30% to 52% and up to three machine passes. Results: The relative increase in bulk density differed between treatments. In the non-assisted corridors, the bulk density increased by 18%, 12%, and 11% at depths of 0–10, 10–20, and 20–30 cm, respectively; the winch-assisted corridors showed smaller increases of 12%, 5%, and 3% at the corresponding depths. The winch-assisted plots did not show a significant reduction in rut depth compared with the non-assisted plots, a result likely influenced by site-specific dry soil conditions. Conclusions: These results highlight the potential of winch-assisted systems to reduce horizontal soil disturbance, though their effectiveness in limiting rutting remains variable under dry conditions.
This study was conducted to analyze the physical strain with heart rate monitor in timber harvesting operations in order to reduce occupational accidents. The timber harvesting activities are manual cutting(felling, limbing and bucking) with a chainsaw and extraction by cable yarder. The study took place on Japanese larch stand. The average height was 26m and average diameter at breast height(DBH) was 3 7cm. The havest unit was gentle slope to steep slope. Results showed that the heart rate increases for chocking, felling, limbing and bucking were 94.0%, 87.9%, 84.8% and 56.4% respectively. The rate of Work Load Index was higher in the limbing(61.4%) activity than other activities chocking(55.2%), felling(54.1%) and bucking(32.1%). During 50% working heart rate test it was found that limbing(1.09), chocking(1.05) and felling(1.04) was exposed to high work intensity compared to bucking(0.83). The results showed that maximum acceptable work times(felling, chocking and limbing) were 2.30 hour, 1.85 hour and 1.60 hour respectively. To avoid occupational accidents, timber harvest workers may use a suitable working hour schedule to felling, chocking, limbing.
Cable yarding technology remains the most effective operation in steep terrain harvesting systems; however, it has limitations and challenges. Using cable yarders (tractor-, truck-, and excavator-based) to extract tree lengths and whole trees has been common since the late 20th century in South Korea, and cable yarding operations were developed in the late 1800s in the United States and Europe. Machine potential and limitations must be understood to ensure the widespread use of technology, strong cooperation, and optimal selection of machinery size. We reviewed the literature on tower yarder performances from 1990–2021 to determine the alteration of yarders and its productivity pattern and obtained 23 papers; <2 publications per year discussed the determination of cable yarding productivity. We selected independent variables (e.g., silvicultural treatment, harvesting method, and cycle log volume) for cable yarding that would likely affect productivity. Data were analyzed to compare productivities under silvicultural treatment, the harvesting method, and yarding direction and identify the interaction mechanical power (i.e., lifting capacity and machine power), yarding distance, and slope. Cable yarder productivity rates generally depended on the silvicultural treatment, harvesting method, and yarding direction, particularly in clear-cut, tree-length, and uphill yarding operation activities. The lifting capacity, machine power, and slope had no significant correlation with yarders’ productivity, particularly in thinning operations, whereas, in clear-cut productivity, it was influenced by these variables. The results contribute to improving operation activities for cable yarding systems and towards future research directions.
No abstract is provided for this article.
No abstract is provided for this article.
Open pile burning (OPB) forest residues have been limited due to several concerns, including atmospheric pollution, risk of fire spread, and weather conditions restrictions. Air Curtain Burner (ACB) systems could be an alternative to OPB and can avoid some of the negative effects that may result from OPB. The main objective was to compare the burning consumption rates and costs of two types of ACB machines, the S-220 and BurnBoss. In addition, we tested a hand-pile burning (HPB) consumption rate for a comparison with BurnBoss unit. The S-220’s burning consumption rates ranged between 5.7 and 6.8 green metric ton (GmT)/scheduled machine hour (SMH) at a cost between US $12.8 and US $10.8/GmT, respectively. Costs were 70% higher when using the BurnBoss unit. Burning residue consumption rates and cost of disposal were considerably different: they were highly dependent on machine size, species, and fuel age of forest residues. Particularly, BurnBoss test burned over 40% more than HPB method and produced clean burn by airflow. The results from this study suggest that ACBs can be a useful tool to dispose of forest residues piled in many forests areas with less concerns of air quality and fire escape risks.
No abstract is provided for this article.
Salvage logging of nematode-infested pinewoods could increase in South Korea, because of the risk of pest spread in response to climate change. No previous studies have precisely determined how to extrapolate information regarding cable extraction productivity and cost in salvage logging operations to steep terrains in South Korea. Therefore, in this study, the performance of a semi-mechanized system was observed at two different harvesting sites located in areas affected by the pinewood nematode (Bursaphelenchus xylophilus). The following were the specific aims of this study: (1) to evaluate HAM200 yarder productivity and cost in four different conditions (50 and 100 m yarding distances in uphill and downhill directions), and (2) to identify significant independent variables related to productivity. The HAM200 productivity values varied considerably and ranged from 1.95 to 2.52 m3/productive machine-hour (costs 43.29–55.81 US $/m3, respectively). Overall, productivity for trees damaged by uphill yarding was 20% higher compared to downhill yarding while productivity was not significantly different. Yarding direction, lateral distance, volume per cycle, and interaction of volume per cycle with lateral distance significantly affected the productivity. Further, our regression model, uphill yarding should be favorable from 35 to 100 m yarding distances. The findings of this study would enable better planning and decision-making regarding salvage logging, thereby allowing improved production of damaged trees.
In South Korea, logs for low-value products, such as pulpwood and fuelwood, are primarily extracted from harvest sites and transported to roadside or landing areas using small shovels. Previous studies on log extraction, however, have focused on cable yarding operations with the goal of improving productivity on steep slopes and inaccessible sites, leaving small-shovel operations relatively unexamined. Therefore, the main objectives were to determine small-shovel extraction productivity and costs and to evaluate the impact of related variables on productivity. In addition, we developed a model to estimate productivity under various site conditions. The study took place in 30 case study areas; each area has trees with stems at a diameter at breast height ranging from 18 to 32 cm and a steep slope (greater than 15%). The areas ranged from 241 to 1129 trees per hectare, with conifer, deciduous, and mixed stands. Small-shovel drives ranged from 36 to 72 m per extraction cycle from stump to landing. The results indicated that the mean extraction productivity of small-shovel operations ranged between 2.44 to 9.85 m3 per scheduled machine hour (including all delays). At the forest level, the estimated average stump-to-forest road log production costs were US $4.37 to 17.66/m3. Small-shovel productivity was significantly correlated with stem size (diameter at breast height and tree volume) and total travelled distance (TTD). However, a Pearson’s correlation analysis indicated that stand density and slope did not have a significant effect on productivity. Our findings provide insights into how stem size and TTD influence small shovel performance and the predictive ability of productivity. Further, this information may be a valuable asset to forest planners and managers.
