Selective lignin decomposition and nitrogen mineralization in forest litter colonized by Clitocybe sp.

摘要

Fruiting bodies of Clitocybe sp. were encountered in association with partly decomposed litter materials that were bleached due to colonization by mycelia of this fungus. We clarified the impact of this fungus on the chemical and fungal properties of litter materials and quantitatively evaluated the potential ability of this fungus to cause selective decomposition of recalcitrant compounds such as lignin. The content of acid-unhydrolyzable residues (AUR) was lower, and the contents of soluble carbohydrates and nutrients (N, P, K, Ca, Mg) and net mineralization rate of N were higher in bleached litter materials (BLM) than in adjacent nonbleached litter materials (NBL). Total hyphal length was 5.4 times greater in BLM than in NBL. A total of 49 fungal taxa were isolated, 30 from BLM and 42 from NBL. In pure culture decomposition tests, Clitocybe sp. caused greater mass loss in partly decomposed leaves than in freshly fallen leaves, which was attributed to the greater mass loss of AUR and more selective decomposition of AUR in partly decomposed leaves. Fourier transform infrared (FT-IR) spectroscopy showed that Clitocybe sp. was responsible for the selective transformation of the chemical structure of lignin. These results showed that Clitocybe sp. had a marked ability to remove AUR and lignin selectively from partly decomposed leaves and to enhance N mineralization, contributing to small-scale heterogeneity of the decomposition within the forest floor.