Effects of forest management on truffle abundance and squirrel diets
Colgan, W., I.II
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Thinning and retention of biological legacies (large live, dead, and fallen trees and their associated biota) during clearcutting are two practices to promote development of late-seral attributes in second-growth forests. We evaluated the effects of these practices on production of truffles and use of truffles as food by northern flying squirrels and Townsend's chipmunks in 55-65-yr-old Douglas-fir forests in the Puget Trough of Washington. Truffles were collected at 6-wk intervals from March 1993 through December 1995. Feces were collected from flying squirrels and chipmunks in fall and spring, 1991-1995, and relative frequencies of truffle genera and vascular plant parts therein were determined. Mean standing crop biomass of truffles did not differ between thinned and legacy forests. However, dominant genera of truffles in the soil and in feces did. Truffles in soil and in flying squirrel diets were more diverse in legacy than in thinned forest. Gautieria, a consistently important component of flying squirrel diets, but not chipmunk diets, was more abundant in legacy than in thinned forest. Melanogaster, eaten by both chipmunks and flying squirrels, was more abundant in thinned than in legacy forest, as were vascular plants. Chipmunks consumed large amounts of vascular plant material. Flying squirrels also consumed plant parts in thinned forest, but they did not consume measurable amounts of plant materials in legacy forest. Flying squirrels consumed a greater diversity of truffles than we found with intensive random sampling. The ability of flying squirrels to find truffles, their propensity to ingest all species of truffles, their excretion of viable spores, and their wide travels makes them important in maintaining the diversity of ectomycorrhizal fungi.