No abstract is provided for this article.
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.
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.
Unpaved forest roads are common accessways in mountain areas being used for forestry purposes. The presence of forest roads produces large volumes of surface runoff and sediment yield due to changes in soil properties and hillslope profile. Rainfall simulation experiments were conducted to estimate the impacts of above-ground vegetation and antecedent soil water condition on hydrology and sediment processes. A total of 9 small plots(<TEX>$1m{\times}0.5m$</TEX>) were installed to represent different road surface conditions: no-vegetation(3 plots), vegetated surface(3 plots), and cleared vegetation surface(3 plots). Experiments were carried out on dry, wet, and very wet soil moisture conditions for each plot. Above ground parts of vegetation on road surface influenced significantly on surface runoff. Runoff from no-vegetation roads(39.24L) was greater than that from vegetated(25.05L), while cleared-vegetation condition is similar to no-vegetation roads(39.72L). Runoff rate responded in a similar way to runoff volume. Soil erosion was also controlled by land cover, but the magnitude is little than that of surface runoff. Even though slight differences among antecedent soil moisture conditions were found on both runoff and soil erosion, runoff rate and soil losses were increased in very wet condition, followed by wet condition. The experiments suggest that vegetation cover on forest road surface seems most effective way to reduce surface runoff and soil erosion during storm periods.
Cable yarding operations on steep terrain have always been a challenge with respect to safety as they are mostly undertaken by manual laborers, particularly in South Korea.Steep slopes are associated with a high workload for choker setters.Therefore, the main goals of this study were to determine the heart rate and oxygen consumption of choker setters and evaluate their workload during clear-cut operations on a Larix kaempferi stand using a Polar M400, H7 heart rate sensor.Three choker setters were continuously evaluated during one working day.Overall, the mean working heart rate (HR w ) during choking operations ranged from 87 to 104 bpm at a maximum oxygen consumption rate of 0.9 to 1.4 L/min.The choker setters recorded most of the effective work time on the "wait" (68.5%) and "walk-in" (7.8%) work elements.In addition, the physiological workload differed among the various elements of the cable yarding operation, with a higher HR w associated with a higher workload.Our findings may provide useful information for managing the health and safety of forestry crews during cable extraction activities.
No abstract is provided for this article.
This study purposed to examine the water retention capacity of floor litter in deciduous forests. Water holding capacity(WHC) and interception storage capacity of Alnus hirsuta Turcz. ex Rupr., Quercus acutissima, Quercus mongolica litters were experimentally estimated. Physical characteristics of litters were also obtained to understand the relationships between water-retention capacity and litter characteristics. Experiments showed that WHC increases with specific volume of litter, varying 244.4% to 416.8% of its dry mass. Interception storage have estimated with rainfall simulation experiments. Maximum interception storage (<TEX>$C_{max}$</TEX>) and minimum interception storage (<TEX>$C_{min}$</TEX>) of litters were 220% and 138% of dry mass in Alnus hirsuta Turcz. ex Rupr., 218% and 137% in Quercus acutissima, and 240% and 156% in Quercus mongolica. Both <TEX>$C_{max}$</TEX> and <TEX>$C_{min}$</TEX> increased linearly with litter mass, and the values of <TEX>$C_{min}$</TEX> in broadleaf litters have also linear relation to leaf area.
Tree diameter, topography, and stand accessibility have been major factors to consider when selecting the optimal equipment to extract logs from stump to landing area. In Korea, forest land has 6.4 million ha of forest, comprising 64% of its total land area. Small and medium (15–30 cm in diameter at breast height [DBH]) size of trees located on steep slopes (> 30°) is approximately 80% of total forest area. Therefore, there has been an increasing interest in the application of a small-scale cable yarding system. We performed uphill and downhill yarding experiments using an 80 hp farm tractor mounted tower yarder (HAM300) to evaluate productivities and costs associated with primary transportation of tree length logs in mixed conifer stands. In addition, sensitivity analyses were performed to find the effects of different yarding directions and distances on yarding productivities and costs. Results showed that uphill and downhill yarding productivities were 9.04 m3/PMH (Productivity Machine Hours) and 7.87 m3/PMH at a cost of US$9.06 and US$10.04/m3, respectively. The yarding direction greatly affected productivity and cost: decreasing productivity may be significantly affected by working conditions. Our results support the effectiveness of an HAM300 yarder in extracting logs for small-scale cable yarding operations.
Recently, the use of powerful and heavy vehicles for timber harvesting on flat or slightly sloping terrains has been widely expanded to provide safe working conditions and high productivity. However, soil disturbances during ground-based mechanized operations in South Korea are not fully investigated and difficult to avoid. Therefore, we compared the soil displacement and compaction (bulk density and hydraulic conductivity) between two different operations: cut-to-length (CTL) logging with a harvester and forwarder, and whole-tree (WTH) logging with a harvester and skidder. After clear-cutting, severe visual disturbances and rut depths were more prevalent in the forwarding trails than in the skidding trails. The CTL harvesting method created larger amounts of slash (6.9 kg/m2) along the trails than the WTH harvesting did (1.8 kg/m2). We found a significant difference in the compaction between the reference and the track and a negative correlation between the slash quantity values and the percentage increase in compaction. Our results showed that using skidding extraction can cause more severe impacts than forwarding extraction. Thus, these results may be helpful in understanding the influence of ground-based CTL and WTH harvesting operations and achieving best practices to minimize the environmental impacts on soil.
No abstract is provided for this article.
Natural forest regeneration offers economic, ecological, and environmental advantages over artificial regeneration; however, its application is often constrained by uncertainties in stand development and management outcomes. Pre-commercial thinning (PCT), a key assisted natural regeneration practice, is widely used to regulate stand density and improve early stand development. Nevertheless, empirical evidence remains limited regarding how post-thinning residual density influences both tree growth and operational performance in high-density naturally regenerated Pinus densiflora stands. This study evaluated three residual density treatments (RD2000, RD3000, and RD5000) following PCT in naturally regenerated pine stands with an initial density of approximately 30,000 stems ha−1. Diameter at breast height, tree height, and crown area were monitored annually over three years, while thinning productivity and operational costs were quantified during treatment implementation. Residual density significantly affected both biological and operational outcomes. The intermediate residual density (RD3000) showed the most consistent growth responses, whereas the lowest residual density (RD2000) resulted in suppressed growth. The highest residual density (RD5000) achieved the highest productivity and lowest operational costs despite moderate growth performance. These results indicate a trade-off between growth performance and operational efficiency and suggest that an intermediate residual density may provide a balanced strategy for managing naturally regenerated pine stands.
Rainfall-induced landsliding is the major sediment-related disaster in the mountainous regions of Korea. Landslide susceptibility mapping, which is the principal approach to identifying areas prone to landslides, provides decision-makers with the policy priorities...
Two integrated harvesting methods have been primarily applied to increase the opportunity for forest biomass utilization. In Korea, small shovels with a carrier for cut-to-length harvesting (CTL system) and tower yarders for whole-tree harvesting (WT system) are commonly used for the transportation of tree assortments (i.e., sawlogs and logging residue). No previous studies are available in South Korea that have compared and highlighted the operational performance and yield of logging residues between the CTL and WT harvesting systems. Thus, our study’s main objectives were to (1) evaluate the productivity and costs of the two harvesting systems through a standard time study method and (2) estimate the amount of harvesting logging residue at the landing. The productivities of the CTL and WT systems were 1.45 and 2.99 oven-dried tons (odt)/productive machine hour (PMH), at a cost of 86.81 and 45.41 USD/odt, respectively. In the WT system, the amount of logging residue (2.1 odt/ha) collected at the landing was approximately four-times larger than that of the CTL system (0.5 odt/ha). Our results suggested that the WT system is a less expensive and more suitable system when there are markets demanding logs and biomass, whereas the CTL system remains a less expensive option for stem-only harvesting. Furthermore, these results are important for estimating the economic and environmental amount of residue that could be potentially recovered and utilized from the forest types included in the study.
우리나라에서는 매년 태풍 혹은 국지성 집중호우로 유발되는 산지토사재해로 인한 피해가 발생하고 있다. 특히, 국립공원 지역은 대부분 산악지로 이루어져 있고 지형의 경사가 가파르고 토심이 얕아 많은 피해가 발생하고 있다. 본 연구는 산악형 국립공원(설악산, 소백산, 지리산)지역에서 발생한 산사태 발생지 446개소를 대상지로 선정하여 다양한 산림환경 인자별로 조사하고 산사태발생지 특성을 분석하였다. 산사태 발생 평균면적, 평균 침식량, 평균 길이, 폭은 각각 1,212 ㎡, 1,389 ㎥, 75 m, 12.9 m로 나타났다. 산림환경 인자가 산사태 발생 빈도에 미치는 영향을 분석한 결과, 사면경사도 (31~40°), 사면방위 N(북사면), 종단·횡단사면 오목(凹), 표고(401~800 m), 사면위치 산복, 하천차수 1차, 임상 혼효림, 모암 화강암, 토심 (46 cm 이상)에서 발생빈도가 높은 것으로 조사되었다. 산사태가 발생한 피해지에서의 침식량과 산림환경 인자와의 상관관계를 분석한 결과는, 종단사면(복합), 표고(1,201 m 이상), 토심(46 cm 이상)에서 1% 수준 내에서 정의상관관계를 보였다. In korea, debris-flow disasters are induced by typhoon and localized torrential rainfall annually. These disasters are particularly severe in the Korean national park due to its geomorphological characteristics. This study was conducted to analyze the landslide characteristics and forest environmental factors of landslide areas located in rugged mountain range in the Korean national park (Mt. Seorak, Mt. Jiri, and Mt. Sobaek). Overall, landslides occurred at 474 sites. The average area of the landslide scar among these sites was 1,212 ㎡. The average landslide sediment was 1,389 ㎥, average landslide length was 75 m, and the average width was 12.9 m. The landslides frequently occurred in regions with igneous rock and coniferous forest. In addition, slope gradient degree (31°-40°), slope gradient direction (N), vertical slope (concave), cross slope (concave), altitude (401-800 m), position (middle), stream order (first order), forest type (mixed), parent rock (igneous), and soil depth (<46 cm). The relationship between landslide soil volume and environmental factors showed positive correlation. The variables of vertical slope (complex), altitude (<1,201 m), and soil depth (<46 cm) correlated significantly at 1 % level.
Comminution is performed by using two main types of machines: grinders and chippers. Grinders are commonly used to treat contaminated wood biomass. In South Korea, cut-to-length harvesting is the main salvage logging method, and felled trees and residues often become dirtied during extraction, where logs are moved from the stump to the roadside using a small shovel. Therefore, grinders are preferred for the comminution of wood biomass for conversion into hog fuel. This study aimed to evaluate productivity and hog fuel quality as outcomes of wood biomass sorting. The productivities for unsorted residues and logs were 11.2 ± 1.48 ton/PMH0 and 12.4 ± 1.73 ton/PMH0 at a moisture content of 24%, respectively. Between 33.5% and 46.0% of the total hog fuel mass passed through the screen and reached an acceptable size (3.15 mm to 63 mm). The bulk densities of the two materials ranged from 132.4 kg/m3 to 148.8 kg/m3 on a dry basis. The results of this study suggest that sorting the feedstock has the potential to reduce the number of oversized particles in the hog fuel without screening.
Larix kaempferi (Lamb.) Carr. plantations are a reasonable alternative to timber production for producing high-quality wood for South Korean industrial applications that need appropriate and high-quality practice of silvicultural operations. Weeding and tree pruning operations, which can favor trees in their competition with vegetation, require intensive manual labor. Therefore, the objective of this study was to determine the effect of these operations on the heart rate variability, relative heart rate (RHR), and physical workload of workers in April (spring) and July (summer) months. Our results showed that the mean heart rate variability and RHR for weeding (108.0 bpm and 49.4%, and 105.8 bpm and 46.8% for worker A and B, respectively) and tree pruning (104.5 bpm and 46.1%, and 114.4 bpm and 55.9% for worker A and B, respectively) in July were higher than those in April. In addition, the level of workload in July was characterized as heavy to very heavy, and as moderate to heavy in April. The results from this study provide useful information for appropriate young tree tending operations from the perspective of the safety and health of workers.
