Effect of downed trees on harvesting productivity and costs in beetle-killed stands

Abstract

The mountain pine beetle (Dendroctonus ponderosae) has affected millions of acres of forests in the Rocky Mountain region in the United States. This study quantified the difficulty of harvesting beetle-killed stands caused by downed trees. A detailed time study was conducted on a whole-tree clearcut harvest using a ground-based system in western Montana in August 2015. Our study shows that the productivity of the feller-buncher was highly affected by the number of downed trees. The feller-buncher average cycle time per tree was 7.0 s when only standing trees were cut and bunched whereas it took 13.2 s per tree when the bunch included one or more downed trees. Our results also indicate that stand conditions with various levels of downed trees affect the unit production cost and productivity of the entire harvesting system by increasing operational delays in the combined felling, skidding, and delimbing operation. This research provides insight into how optimized system configurations may help cope with the increase in harvesting cost caused by beetle-killed stand conditions and helps quantify the potential financial impacts of delayed stand management decisions in the wake of high-mortality forest disturbances.