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Title: Silviculture affects composition, growth, and yield in mixed northern conifers: 40-year results from the Penobscot Experimental Forest
Author: Sendak, Paul E.; Brissette, John C.; Frank, Robert M.
Publication: Canadian Journal of Forest Research. 33: 2116-2128.
Abstract: This long-term experiment in Maine, U.S.A., was designed to provide information on the best silvicultural practices for managing stands of mixed northern conifers in northeastern U.S.A. We evaluated growth and yield and changes in species composition, quality, and structure during the first 40 years of the experiment. Replicated treatments include the selection system, uniform shelterwood, unregulated harvesting, and diameter-limit cutting. The new cohort established under three-stage shelterwood was subsequently left untreated or precommercially thinned. Between treatment differences in net volume growth were not significant (a = 0.10), though gross volume growth differed significantly for managed vs. unmanaged, selection vs. shelterwood, and shelterwood vs. diameter-limit treatments. A three-stage shelterwood method with precommercial thinning 10 years following final overstory removal resulted in good control of hardwoods and hemlock and a dramatic increase in spruce and fir. The selection system on a 5-year cutting cycle resulted in increased hemlock, spruce, and fir, with a decrease in hardwood species. If the primary goal were production, even-aged management would most likely be preferred. We recommend a two-stage shelterwood method as applied in this experiment with some modification to improve species composition and stand quality. Stand quality (proportion of stand volume in cull trees) and species composition was influenced by treatment.
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