Productivity and cost of a small-scale cable yarder in an uphill and downhill area: a case study in South Korea

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.