Evaluating the long-term influence of alternative commercial thinning regimes and harvesting systems on projected net present value of precommercially thinned spruce-fir stands in northern Maine

Commercial thinning (CT) is an important silvicultural practice in the northeastern US. Relatively little is known, however, about the interaction of harvest system and treatment (removal intensity or timing of entry) on the overall profitability of CT. To address this question, ten-year measurements from a controlled CT experiment across six sites in Maine were used to project the long-term effect of removal intensity (33% and 50% relative density reduction) and timing of entry (no-delay, 5-year delay, 10-year delay) on: (1) maximum net present value (NPV), (2) timing of maximum NPV, and (3) the effect of three harvesting systems (cut-to-length, whole-tree, hybrid system) on maximum NPV. A regional growth and yield model was used to project individual-tree growth and mortality into the future. Harvest costs for the harvesting systems were estimated using regional cycle-time equations. No difference was found in maximum NPV between the CT and non-CT areas, or the timing of CT entry. Stand age at time of maximum NPV differed between delays but not between the two removal intensities. Our results indicate that there is no economic benefit in delaying a CT nor removing more volume at the time of thinning for the range of stand conditions evaluated.

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