Lignin-degrading ability of litter-decomposing basidiomycetes from Picea forests of Hokkaido

The frequency of occurrence of the litter-decomposing basidiomycetes of Picea abies and P. glehnii forest floors in Hokkaido was investigated. In both the P. abies and P. glehnii forest plots (each 10m x 10m), litter-decomposing basidiomycetes of the genera Collybia and Mycena were frequently observed. Species composition, frequency of occurrence, and basidioma numbers of each species were different between the two forest plots, but several species were common to both. Seven species isolated from the P. glehnii forest plot (C. acervata, C. pinastris, Marasmius pallidocephalus, Ma. wettsteinii, My. aurantiidisca, My. clavicularis, Mycena sp. 1) and four species from the P. abies forest plot (C. pinastris, My. alphitophora (= My. osmundicola), Mycena sp. 1, My. vulgaris) were tested for their ability to degrade lignin by a simple plate test for extracellular phenoloxidases and by measuring Klason lignin loss from needle litter of spruce. All the strains of the litter-decomposing fungi tested showed positive reactions on the plate test. Lignin contained in the needle litter was degraded by all strains tested (only My. alphitophora was not tested), and rates varied from 9% to 40% over a two-month period in vitro. Seven species with ligninolytic ability in the P. glehnii forest plot and four such species in the P. abies forest plot were found respectively in 77% and 60% of the 100 subplots in each plot. The results of this study suggest that lignin decomposition of needle litter by litter-decomposing basidiomycetes in the forest floor is a common event in the studied Picea forests of Hokkaido and that the diversity of the ligninolytic activity among the species or strains may cause spatial heterogeneity of litter decomposition in the Picea forest floor.