Predictors of diversity of deadwood-dwelling macrofungi in a European natural forest

Abstract Deadwood plays a crucial role in the maintenance of biodiversity in forest ecosystems. Its quantity and quality are commonly used in ecology and nature conservation as a proxy indicator of forest biodiversity. In this study we exposed 720 logs of wood in a full-factorial experiment, set in a temperate European forest, to test the influence of forest type (three levels), host wood identity (four species) and degree of contact with soil (three levels) on species richness and species composition of wood-inhabiting macrofungi. The forest type did not influence the taxon richness and had limited influence on the composition of deadwood-dwelling mycobiota. The degree of contact with soil was an important factor, with the taxon richness of the subterranean logs extremely low and their fungal composition being a subset of the species pools of logs lying on the soil surface and those hanging above the ground. The host wood identity was the strongest predictor of taxon richness and composition of macrofungi: Carpinus betulus wood hosted the highest, Quercus robur the medium, and Picea abies and Pinus sylvestris ex aequo the lowest taxon richness of fungi. Fungal communities differed significantly between all host wood species with the exception of conifers, which hosted similar mycocoenoses. Our study indicates that host wood identity and degree of log contact with soil are the most important factors determining macrofungal communities in deadwood, overriding the influence of forest type. Taking into account the degree of wood debris contact with soil revealed that the common practice of leaving subterranean wood biomass (stumps and root systems) in logged forests does not have any importance for the diversity of macrofungi. Thus, a reasonable amount of diverse above ground wood debris needs to be left (or brought from outside) to maintain the diversity of the forest ecosystems.