Continental-scale macrofungal assemblage patterns correlate with climate, soil carbon and nitrogen deposition

Aim: Macroecological scales of species compositional trends are well documented for a variety of plant and animal groups, but remain sparse for fungi, despite their ecological importance in carbon and nutrient cycling. It is, thus, essential to understand the composition of fungal assemblages across broad geographical scales and the underlying drivers. Our overall aim was to describe these patterns for fungi across two nutritional modes (saprotrophic and ectomycorrhizal). Furthermore, we aimed to elucidate the temporal component of fruiting patterns and to relate these to soil carbon and nitrogen deposition. Location: Central and Northern Europe. Methods: A total of 4.9 million fungal fruit body observations throughout Europe, collected between 1970 and 2010, were analysed to determine the two main environmental and geographical gradients structuring fungal assemblages for two main nutritional modes, saprotrophic and ectomycorrhizal fungi. Results: Two main gradients explaining the geography of compositional patterns were identified, for each nutritional mode. Mean annual temperature (and related collinear, seasonal measures) correlated most strongly with the first gradient for both nutritional modes. Soil organic carbon was the highest correlate of the second compositional gradient for ectomycorrhizal fungi, suspected as an indicator of vegetation- and pH-related covariates. In contrast, nitrogen deposition constituted a second gradient for saprotrophic fungi, likely a proxy for anthropogenic pollution. Compositional gradients and environmental conditions correlated similarly when the data were divided into two time intervals of 19701990 and 19912010. Evidence of compositional temporal change was highest with increasing elevation and latitude. Main conclusions: Fungal assemblage patterns demonstrate clear biogeographical patterns that relate the nutritional modes to their main environmental correlates of temperature, soil organic carbon and nitrogen deposition. With respect to global change impacts, the highest rates of compositional change by time suggest targeting higher latitudes and elevations for a better understanding of fungal dynamics. We, finally, suggest further examination of the ranges and dispersal abilities of fungi to better assess responses to global change.