Distribution of ectomycorrhizas in micro-habitats in mature and old-growth stands of Douglas-fir on southeastern Vancouver Island

Abstract

Knowledge of the functional diversity of ectomycorrhizas is needed to design forest management practices that sustain both commercial yield of timber and biological diversity. We surveyed the distribution of ectomycorrhizal types in logs, stumps, the forest floor and mineral soil, in mature (90-y) and old-growth (290, 440 y) stands of Douglas-fir [ Pseudotsuga menziesii (Mirb.) Franco]. Ectomycorrhizal abundance (root-tips l −1 of soil) and frequency (occurrence in soil cores) were related to soil chemical characteristics and habitats. Density of ectomycorrhizal rooting was greater in the forest floor (LFH) over mineral soil (114 tips l −1) than in mineral soil (28) or logs (46). Logs contained more ectomycorrhizal root tips and more types of ectomycorrhizas than stumps. Piloderma fallax (Libert) Stalpers preferred woody substrate; two unidentified types, including “ Pseudotsugarhiza baculifera” ( Piloderma?) (Mueller, W. R. and Agerer, R. (1996) “ Pseudotsugaerhiza baculifera”+ Pseudotsuga menziesii (Mirb.) Franco. In Descriptions of Ectomycorrhizae, ed. R. Agerer, pp. 95–100. Einhorn-Verlag, 73502 Schwabisch Gmund, Munich.), were found almost exclusively in the forest floor and coarse woody debris and another unidentified type (CDE3) was found only in mineral soil. There was little correlation between ectomycorrhizal abundance and chemical content of soil cores, perhaps due to heterogeneity of soil environment within cores. Future studies might best focus on particular fungi or microhabitats.