The structure of micromycete communities and their synecologic interactions with basidiomycetes during plant debris decomposition

We investigated the interactions between micromycetes and basidiomycete mycelium on plant substrates in the course of their 3-year incubation in the litter of ecologically intact spruce forests of the Central Forest State Biosphere Reservoir (Nelidovo district, Tver oblast). Only 40–60% of the micromycetes were involved in direct antagonistic interactions with basidiomycetous fungi. In terms of the ratio between physiologically active strains and those that did not interact with basidiomycete mycelium, we revealed differences in the structure of micromycete communities developing on various types of substrates (wood, bark, sphagnum moss, leaves, needles, litter, and cotton grass). The micromycetes tested belonged to 49 species. At the end of the observation period, the fraction of microscopic fungi that actively influenced basidiomycete mycelium was four times lower in the inactive litter fraction (lignin-containing wood debris) than in the active fraction (grass substrates). The mechanisms of indirect regulation of the structure and functions of micromycete communities are discussed, which may be based on the accumulation of phenolic compounds in the medium and changes in the enzyme activities of basidiomycete mycelium.