Hagiwara Yusuke, Matsuoka Shunsuke, Hobara Satoru, Mori Akira S, Hirose Dai, Osono Takashi
a Center for Ecological Research, Kyoto University, Otsu, Shiga 520-2113, Japan.
b Department of Environmental Symbiotic Sciences, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan.
Can J Microbiol. 2015 Oct;61(10):735-43. doi: 10.1139/cjm-2015-0111. Epub 2015 Jun 16.
Fungal decomposition of lignin leads to the whitening, or bleaching, of leaf litter, especially in temperate and tropical forests, but less is known about such bleaching in forests of cooler regions, such as boreal and subalpine forests. The purposes of the present study were to examine the extent of bleached area on the surface of leaf litter and its variation with environmental conditions in subboreal and subalpine forests in Japan and to examine the microfungi associated with the bleaching of leaf litter by isolating fungi from the bleached portions of the litter. Bleached area accounted for 21.7%-32.7% and 2.0%-10.0% of total leaf area of Quercus crispula and Betula ermanii, respectively, in subboreal forests, and for 6.3% and 18.6% of total leaf area of B. ermanii and Picea jezoensis var. hondoensis, respectively, in a subalpine forest. In subboreal forests, elevation, C/N ratio and pH of the FH layer, and slope aspect were selected as predictor variables for the bleached leaf area. Leaf mass per area and lignin content were consistently lower in the bleached area than in the nonbleached area of the same leaves, indicating that the selective decomposition of acid unhydrolyzable residue (recalcitrant compounds such as lignin, tannins, and cutins) enhanced the mass loss of leaf tissues in the bleached portions. Isolates of a total of 11 fungal species (6 species of Ascomycota and 5 of Basidiomycota) exhibited leaf-litter-bleaching activity under pure culture conditions. Two fungal species (Coccomyces sp. and Mycena sp.) occurred in both subboreal and subalpine forests, which were separated from each other by approximately 1100 km.
真菌对木质素的分解导致落叶变白，即漂白，这在温带和热带森林中尤为明显，但对于寒温带和亚高山森林等较寒冷地区森林中的这种漂白现象，人们了解较少。本研究的目的是调查日本亚寒带和亚高山森林中落叶表面漂白区域的范围及其随环境条件的变化，并通过从落叶漂白部分分离真菌来研究与落叶漂白相关的微真菌。在亚寒带森林中，柞木和岳桦的漂白面积分别占总叶面积的21.7%-32.7%和2.0%-10.0%，在亚高山森林中，岳桦和日本云杉的漂白面积分别占总叶面积的6.3%和18.6%。在亚寒带森林中，选择海拔、FH层的碳氮比和pH值以及坡向作为漂白叶面积的预测变量。同一叶片的漂白区域的单位面积叶质量和木质素含量始终低于未漂白区域，这表明酸性不可水解残留物（如木质素、单宁和角质等难降解化合物）的选择性分解增加了漂白部分叶片组织的质量损失。在纯培养条件下，总共11种真菌（6种子囊菌和5种担子菌）的分离物表现出落叶漂白活性。两种真菌（Coccomyces sp.和Mycena sp.）同时出现在亚寒带和亚高山森林中，这两个森林彼此相距约1100公里。
