No abstract is provided for this article.
No abstract is provided for this article.
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.
Forest roads, haul roads, and especially skid trails have been associated with sedimentation and soil erosion risk. Despite the widespread small shovel harvesting system on steep terrains in South Korea, the subsequent risks of deep (rut depth >5 cm) and compact disturbances, and erosion rates in skid trails are largely unknown. Therefore, the main objectives of this study were to compare the soil erosion rate in each skid trail and predict the total soil erosion rate in a small shovel harvesting area. The soil erosion rate was measured at the plot scale (5 × 3 m) in different skid trail parts (bladed skid trail by small-shovel loader passage, BT; and compacted skid trail CT by carrier passage with construction by a small-shovel loader) using a silt fence experiment. In addition, we investigated the applicability of the Water Erosion Prediction Project (WEPP) model to each disturbance. Among all disturbances, the highest erosion rate (average value of 9.13 ± 0.96 kg m −2 4 months −1 ) was because of CT. The model predictions were over- and under-estimated and showed particularly poor performance where uncovered soil was exposed (less than 1%) to high machine traffic frequency and excavation. Further, the annual soil erosion rates ranged from 11.59 to 28.94 ton ha −1 year −1 . The results suggested that the WEPP model could partially validate the soil erosion results, and further research is still required to improve the accuracy of the model.
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.
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.
불투과형 사방댐에 의한 수질오염 문제는 산림유역관리에 있어 매우 중요하지만, 이에 대한 신뢰할 수 있는 연구는 상대적으로 부족하다. 이 연구에서는 이를 위하여 낙동강유역 사방댐을 대상으로 계류수와 저류수의 수질을 조사하였으며, 수질 특성과 유역의 물리적 환경과의 상관관계를 분석하였다. 전체 43개의 조사대상 사방댐 중에서 농업용수 등급이하로 판정된 곳은 10%미만으로 나타나 전반적으로 수질은 양호하였다. 계류수 및 저류수에서 공통적으로 상관성이 높게 나타난 항목은 TOC와 산소요구량, SS와 탁도, SS와 Chl-a, Chl-a와 탁도 등이었다. 계류수에서 높은 상관성을 보인 항목들은 BOD와 SS, BOD와 Chl-a, BOD와 탁도, TOC와 Chl-a 등이었다. 이 연구의 결론은 사방댐 저류수의 수질이 대부분 양호하였고 저류수 수질이 유출수 수질에 다소 영향이 있지만 개별 수질항목에 국한된다는 것이다. Water pollution in erosion control dams is a major issue for forest watershed management, but the effects of erosion control dams on water quality remain poorly understood. In this study, water quality data from streams and dam reservoirs were collected over the Nakdong river basin. Monitored data were further analyzed to examine the relationship between watershed characteristics and water quality. Of the total 43 erosion control dams, less than 10% had lower water quality that was not suitable for agricultural use. TOC and oxygen demand, SS and turbidity, SS and Chl-a, and Chl-a and turbidity showed high correlations (p < 0.01) both in stream water and in detained water. BOD and SS, BOD and Chl-a, BOD and turbidity, and TOC and Chl-a showed high correlations only in stream water. Overall, the results demonstrated that for most erosion control dams the water quality was relatively good. In addition, the quality of downstream water is somewhat affected by the water detained by erosion control dams, in limited ways.
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.
Typical small shovel logging system, using manual felling and extraction by small crawler excavator with grapple and crawler carriers, is the predominant logging method in the Republic of Korea, due to the associated high productivity. The trails with ground pressure and one more passes of the shovel and carriers may lead to soil compaction. However, impacts of these bunching-extraction technologies on physical and hydrological properties of soils are not well known. The main objectives of this study were to: (1) determine the bulk density, porosity, and saturated hydraulic conductivity of soils in logging operation areas with three different disturbance types (i.e., undisturbed areas [UAs], bladed trails [BTs], and skid trails [STs]), and (2) compare soil compaction between these disturbance types. The most intense compaction occurred within BTs and STs, with increased bulk density and reduced porosity and hydraulic conductivity. Soil bulk density increased by 27–53% at all depths in BTs and STs compared to UAs, while porosity decreased by 23–49%. On average, saturated hydraulic conductivity at depths of 0–20 cm decreased from 337.5 mm h−1 to 30.5 mm h−1 in the most compacted sections of BTs and STs. Skid trails, which are characterized by trail construction and frequent vehicle movement, also caused greater impacts on soil compaction than BTs. This study provides useful insights to aid forest consultants and field managers in planning more environmentally sound mechanized logging operations.
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...
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.
No abstract is provided for this article.
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.
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.
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.
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.
