Wood-decaying fungi in boreal forest: are species richness and abundances influenced by small-scale spatiotemporal distribution of dead wood? Original Research Article

We tested whether the spatiotemporal distribution of Norway spruce (Picea abies) logs influenced species richness and abundances of wood-decaying fungi in two 2-km2 boreal forest study sites in southeastern Norway. According to the random sample null-hypothesis equally large subsamples of logs should be equally efficient in sampling fungi from a regional species pool. Based on 0.25-ha plots at 1-ha grid resolution, we compared plots with high and low densities of ‘new logs’ (decay stages 1–5) and plots with ‘old logs’ (decay stages 5–8) present or absent. Based on visible sporocarps, 45 fungus species, including 15 redlisted, were identified among 4151 logs. When rarefying species accumulation curves to the same number of logs, we found no difference in species richness between old forest plots having high and low densities of new logs, or between plots where old logs were present or absent. Curves from young forest revealed fewer species than in old forest. Multiple regression analysis of six redlisted and six common species corroborated the rarefaction analysis in showing that the probability of occurrence was independent of the spatiotemporal distribution of logs for all but two common species. Aside from the fact that more dead wood harboured more wood-decaying fungi, we conclude that the spatiotemporal distribution of dead wood was of minor importance in determining species richness and abundances at the scales of <1 ha and <100 years. This suggests that wood-decaying fungi are not dispersal-limited at these scales, and it offers an optional element in forest management.