Performance and cost of downhill cable yarding operations in a group shelterwood system

Abstract

ABSTRACTCable yarding operations are conventionally used in steep terrain harvesting, but their share in operations varies widely, tending to be low in many regions. This study evaluated the time consumption, productivity and cost of downhill sledge-yarding operations in group shelterwood extractions deployed in steep terrain beech forests. Relevant operational variables (yarding distance, lateral yarding distance and slope) were selected as predictors to model the time consumption based on a number of 558 work cycles. For an extraction distance of 326 m, a lateral yarding distance of 43 m and a payload of 1.87 m3 per turn, the yarding cycle time was estimated to about 12.5 min. Notable as share in the yarding cycle time were the choking (28%), lateral-in (19%), lateral-out (16%) and unchoking (13%), with the second and the third work elements being significantly affected by very high lateral yarding distances. Estimated productivity and efficiency rates were of 8.80 m3 h−1 and 0.11 h m−3, respectively. Extraction costs were estimated at 7.4 € m−3, in which the operator costs contributed the most (4.3 € m−3). Given the low fossil energy inputs, increased environmental performance due to suspended extraction of the logs, and the acceptable productivity and cost, this system could be extended in low-accessibility, steep-terrain harvesting.