Composition and diversity of fungi on decaying logs in a New Zealand temperate beech (Nothofagus) forest

Saprobic fungal taxa on decomposing mountain beech (Nothofagus solandri var. cliffortioides (Hook. f.) Poole) logs were investigated in relation to properties of logs including stage of decay, size, nutrient concentration, and moisture content. We also determined whether logs become increasingly heterogeneous in nutrient concentration and moisture content with decay and also whether log heterogeneity related to fungal taxa diversity. Sporocarps were collected from the same 75 logs in spring (November 1995, 80 taxa) and autumn (May 1996, 151 taxa). For both seasons the dominant pattern in fungal taxa composition was only weakly related to measured properties of logs; however, a secondary pattern was found related to a fungal taxa succession reflecting stage of decay. In the autumn collection, Biscogniauxia capnodes (Berk.) Y.M. Ju & J.D. Rogers and Schizopora nothofagi (G. Cunn.) P.K. Buchanan & Ryvarden occurred on small logs in the early stages of decay, with relatively low N. Decayed logs, with relatively high N, were characterized by Marasmius otagensis G. Stev. and Athelia epiphylla Pers. Our observations were not consistent with previously described successional trends from soft- to white- and brown-rot fungi as logs decay. The number of fungal taxa increased with log volume, and, additionally for the autumn collection, with heterogeneity in cation concentration suggesting habitat heterogeneity may be a factor in explaining log fungal taxa diversity.