Effects of Pre-Bunching Trees With a Tethered Feller-Buncher on Cable Logging Productivity and Costs: A Case Study in Southern Oregon

Abstract Winch-assist or tethered logging technology is rapidly being adopted by the forest industry across the western United States to replace conventional and dangerous manual tree falling in cable logging areas. Although the safety benefits of the technology are widely acknowledged, the effects of tethered mechanized timber falling and pre-bunching on the subsequent cable yarding operations have not been thoroughly investigated. We conducted a field study in southern Oregon to compare manual versus mechanized timber falling side-by-side for their impacts on the productivity and costs of cable logging operations. Our study shows that the costs of mechanized timber falling were higher than manual falling owing to high costs of tether equipment, but the ability of the felling machine to pre-bunch trees into piles along designated skyline corridors made subsequent cable yarding operations significantly more efficient. The efficiency gained during yarding was sufficient not only to offset cost increase in felling but also to reduce the total production costs of felling and yarding operations by 32% compared with cable yarding after manual timber falling.