The influence of thinning on production of hypogeous fungus sporocarps in Douglas-fir forests in the Northern Oregon Coast Range
Gomez, Douglas M.
Anthony, Robert G.
Trappe, James M.
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Sporocarps of hypogeous fungi are an important food resource for many wildlife species. Effects of thinning second-growth (35 to 45 yr-old) Douglas-fir forests on production of hypogeous sporocarps were investigated to test the hypothesis that in the short term thinning would reduce their production and species diversity. We compared sporocarp production among unthinned, moderately thinned, and heavily thinned stands in four locations in the Oregon Coast Range, 1996 and 1997. Distributions of hypogeous sporocarps were clumped. Total biomass of sporocarps was highest in spring 1996 and progressively decreased in subsequent sampling periods. The genera Alpova, Barssia, Elaphomyces, Truncocolumella, and Tuber appeared to decrease in response to thinning. Thinning significantly reduced total sporocarp frequency among treatments. The mean number of species fruiting was significantly higher in the unthinned than thinned treatments, and more species occurred in the unthinned than thinned treatments in autumn 1996. The array of sporocarp-producing species varied between treatments. Sporocarp distributions were clumped at the plot and grid station levels, and total sporocarp abundance was associated with abundance of coarse woody debris (CWD). These results indicated that commercial thinning influenced hypogeous sporocarp production and sporocarp species diversity at 2 to 3 yr after cutting and that CWD was an important variable for predicting hypogeous sporocarp production. Retention of CWD in commercially thinned sites seems important for sporocarp production of certain hypogeous species and thus to habitat maintenance for many small mammal mycophagists