Is height of dominant trees at a reference diameter an adequate measure of site quality?

Truffles are a staple food source for many forest small mammals yet the vegetation or soil conditions associated with truffle abundance are unknown. We examined the spatial distribution of forest structures, organic layer depth, root density, and two of the most common western North American truffles (Elaphomyces granulatus and Rhizopogon parksii), in managed-young, natural-mature and old-growth western hemlock (Tsuga heterophylla)/Douglas-fir (Pseudotsuga menziesii) stands in Washington State. Forest conditions, E. granulatus and R. parksii sporocarp locations were mapped and analyzed using ARC/ INFO. Spatial patterns were assessed with univariate and bivariate Ripley's K analysis, which measures the scale at which one and two sets of points, respectively, are 'attracted' or 'repelled'. R. parksii truffles were not associated with organic layer depth, root density or forest structure. E. granulatus truffles were distributed in widely-spaced, high-biomass clusters which are significantly associated with thick organic layers with a high density of fine roots. E. granulatus truffles were significantly distanced from trees at 1-2 m. No other associations were found between E. granulatus truffles, logs, ferns or shrubs. Although E. granulatus comprised more than 90% of the total truffle biomass in these unmanaged mature and old-growth stands, in managed-young stands, E. granulatus truffles were rare and total truffle biomass was low. In managed-young stands, organic layer depth and fine root density have been significantly reduced with the introduction of fire. Slash burning and soil scarification practices in these forests may have a strong affect on local food abundance and availability of the most common truffle for small mammal consumers. [ABSTRACT FROM AUTHOR]