Ecology, environmental requirements and conservation of corticioid fungi occupying small diameter dead wood

Abstract

The increasing human impact upon the biosphere of earth is causing profound changes across all spatial scales. The ability to cope with human-induced disturbance varies among organisms; specialist species are more negatively affected than generalist species. Forests are among the most heavily affected ecosystems; especially the dead wood associated organisms are in peril. The earlier research has strongly focused on large diameter dead wood and associated species. The aim of this thesis was to investigate small diameter dead wood and collect systematic information about species richness and abundance as well as habitat and substrate preferences of associated corticioid fungi. Fungal data was collected from four coniferous and three deciduous boreal forest types using a novel, hierarchical sampling method. Altogether 180 325 dead wood units were examined, and 10 217 observations of 276 fungal species detected. Small diameter dead wood proved to be surprisingly species rich substrate, hosting many rare species. Fungal communities associated with small dead wood differed from the communities of larger substrates. No strict specialist species for certain dead wood diameter were found, but species’ preference for either small or large dead wood was evident. The negative effect of forest management was evident also in fungi associated with small dead wood, even though the amount of small dead wood was similar in natural and managed coniferous forests. Higher species richness in natural herb-rich forests compared with wood pastures and afforested fields reflects the differences in their dead wood profiles. As various species thrive also in these secondary forest types, they could serve as surrogate habitats for many broadleaved dead wood associated species. Climate change and increasing energy wood harvesting are causing new threats for wood-inhabiting fungi occupying the smallest dead wood substrates.