Seasonality and sequential occurrence of fungi on wood submerged in Tai Po Kau Forest Stream, Hong Kong

Abstract

The effects of seasonality on freshwater lignicolous fungi in Tai Po Kau Forest Stream was investigated by examining the fungal communities on naturally occurring submerged wood. Fungal succession (sequential occurrence of sporulating fungi) was also investigated by studying changes of fungal communities on wood baits of Machilus velutina and Pinus massoniana over 21 months. Higher species richness, fewer dominant fungi and more infrequent fungi were found on naturally occurring submerged wood during the hot wet season, as compared to the cool dry season. Fungal communities were variable on collections made over different hot wet seasons, but the communities were consistent during the cool dry season collections. Aniptodera chesapeakensis, Massarina ingoldiana and Sporoschisma nigroseptatum dominated the fungal communities during the cool dry season, while Nectria cf. byssicola was dominant during the hot wet season. During 21 months submersion of wood baits of Machilus velutina and Pinus massoniana, three distinct types of fungal communities were observed, i.e. pioneer, early and later successional groups. Higher species richness and more dominant fungi were found on both wood types during the early successional stage. Differences in successional groups were more prominent on wood baits of Pinus massoniana. Fungal communities on wood baits of Machilus velutina and Pinus massoniana were similar during both pioneer and early successional stages, but differed at the later successional stage. Nectria cf. byssicola, Sporoschisma nigroseptatum and S. uniseptatum were early colonisers on both wood types. Savoryella lignicola was a later coloniser on Machilus velutina, while Dictyosporium digitatum, Massarina bipolaris and M. ingoldiana were later colonisers on Pinus massoniana. A total of 175 fungi, including 56 ascomycetes, 1 basidiomycete, 115 anamorphic fungi, 2 myxomycetes and 1 zygomycete, were recorded in this study.