Fungal decomposition of woody debris of Castanopsis sieboldii in a subtropical old-growth forest

Fungi, especially basidiomycetes, are the primary agents of woody debris decomposition in terrestrial forest ecosystems. However, quantitative data regarding the abundance and decay activity of wood-inhabiting fungi are lacking, especially for tropical and subtropical areas. This study demonstrates the dynamics of decay columns of wood-inhabiting fungi within decaying woody debris of Castanopsis sieboldii and the wood decay activities of those fungi in a subtropical natural forest. Among six basidiomycetes and two ascomycetes observed as sporocarps on fallen boles of C. sieboldii, Microporus affinis was most abundantly observed in terms of frequency of sporocarps and as percentage area of decay columns within cross-sections of boles, especially those in the early stages of decomposition. In decay columns of M. affinis, both acid-unhydrolyzable residue (AUR) and holocellulose decayed simultaneously, and wood relative density decreased to 45.8% of that of fresh C. sieboldii wood. A pure culture decay test under laboratory conditions showed that M. affinis was a strong decomposer of AUR and holocellulose. These results suggest that M. affinis has a central role in lignocellulose decomposition of wood of C. sieboldii in the early stages of decomposition.