Tree diameter effects on cost and productivity of cut-to-length systems

Currently, there is a lack of economic information concerning cut-to-length harvesting systems. This study examined and measured the different costs of operating cut-to-length logging equipment over a range of average stand diameters at breast height. Three different cut-to-length logging systems were examined in this study. Systems included : 1) feller-buncher/manual/forwarder ; 2) feller-buncher/processor/forwarder; and 3) swing-to-tree harvester/forwarder. Operating costs were calculated by generating stands with the stand generator program PCWThin. Once stands were generated, costs for thinning were determined using a computer spreadsheet model known as the Auburn Harvester Analyzer. Each individual system followed different cost trends; however, for all systems, tree size had a significant effect on unit cost ofwood produced. As tree size increased, unit cost of wood produced decreased. The swing-to-tree harvester system was much more expensive for small-diameter trees than the other two systems due to individual stem processing and small volume per tree but approached the unit costs of the other systems at larger tree sizes.