Microfungi associated with Abies needles and Betula leaf litter in a subalpine coniferous forest

We investigated microfungal assemblages on leaf litter within a subalpine forest in central Japan and their variation with season, litter depth, and litter species. Microfungal assemblages were compared for Abies needles and Betula leaf litter collected from litter and fermentation layers of the forest floor during the growing season in spring, summer, and autumn. A total of 35 and 42 species were isolated from Abies needles and Betula leaf litter, respectively. The observed variation in microfungal assemblages was primarily attributable to seasonal differences. The frequencies of Trichoderma viride, Volutella ciliata, Mucor sp., and Umbelopsis ramanniana increased in summer, leading to a high degree of similarity of microfungal assemblages in different litter depths and litter species. Microfungal assemblages on Abies needles in spring and autumn and those on Betula leaves in spring were characterized by Trichoderma viride, V. ciliata, Thysanophora penicillioides, Trichoderma polysporum, and (or) Mortierella alpina. Microfungal assemblages on Betula leaves in autumn were characterized by the absence of these species and the occurrence of Cladosporium cladosporioides. The results were discussed with an emphasis on the role of microfungi in decomposition processes and the impact on fungi of predicted future increases in global temperature.