Article Performance Analysis of Log Extraction by a Small Shovel Operation in Steep Forests of South Korea Eunjai Lee 1 , Sang-Kyun Han 2 and Sangjun Im 3,* 1 National Institute of Forest Science, Forest Technology and Management Research Center, 498 Gwangneungsumogwon-ro, Soheul-eup, Pocheon 11186, Korea 2 Department of Forestry and Landscape Architecture, Korea National College of Agriculture and Fisheries, 1515 Kongjwipatwji-ro, Deokjin-gu, Jeonju 54874, Korea 3 Department of Forest Sciences and Research Institute of Agriculture and Life Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Korea * Correspondence: [email protected]; Tel.: +82-2-880-4768 Received: 7 May 2019; Accepted: 11 July 2019; Published: 13 July 2019 Abstract: 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. Keywords: shovel logging; follow-up study; cut-to-length extraction; productivity; cost; scheduled machine hour 1. Introduction Logging operations (a.k.a., primary transportation), in which logs are transported from stumps to a designated roadside or central landing area using various extraction methods, are an important part of the timber harvesting process, but they can be extremely expensive and more time-consuming in practice than felling and processing [1–4]. Many studies have examined the performance of extraction methods on sites with differing characteristics in order to establish the logistics of extraction activities, such as ground-based extraction (skidding and forwarding) [5–8] and cable yarding [8–10]. It can be concluded from these studies that logging practices should be economically determined while maintaining a deep understanding of both the potential and limitations of the chosen method. 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Korea: cut-to-length small-shovel productionTwoharvesting (CTL-S) methodsand tree- arelength commonly cable-yarder used in production South Korea: harvesting cut-to-length (TL- small-shovelC). 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