Impact of Whole-Tree and Cut-to-Length Harvesting on Postharvest Condition and Logging Costs for Early Commercial Thinning in Maine

Regenerating clearcuts dating from the spruce budworm outbreak of the 1980s are beginning to reach merchantable size throughout northern Maine and would benefit from commercial thinning, but there is no consensus among foresters and the logging industry about how such stands can be efficiently thinned. This study investigated silviculturally effective, operational solutions to implement early commercial thinning treatments. Comparisons between two whole-tree (WT) and two cut-to-length (CTL) systems were made in terms of residual stem damage, retention of downed woody material, product utilization, and unit cost of production. Results show significantly more crop trees removed (P = 0.030) and more high severity wound area per plot (P = 0.011) for the WT systems. There was no difference in the number of stems wounded per plot at the high severity level between harvest methods (P = 0.312). Harvest-generated and retained downed wood material volume averaged 511.9 and 205.6 ft3/ac for CTL and WT plots, respectively. Round wood production was the same for CTL and WT plots (average 30 tons/ac), but more than four times more biomass was produced from the WT operations. Production costs were not significantly different between harvest methods due in part to high machine productivity and increased biomass production for the WT systems.