Fungi play important roles in the regulation of C cycling and mediating mineral nutrition of plants. Despite their recognized importance in ecosystem functioning, we lack a clear understanding of the response of soil fungal communities to simultaneous multiple global change drivers (e.g., N and Hg deposition) from variability in soil biogeochemical properties (e.g., soil C, C:N) and plant diversity (i.e., NPP). Toward this goal, we investigated the effects of climate, host plant and soil properties in structuring soil fungal diversity and community composition using soil biogeochemical and high-throughput sequence data from 12 sites across North America collected by the National Ecological Observatory Network (NEON), ranging from northern hardwood forests to the central plains. We integrated these results with environmental and remote sensing data obtained from the National Atmospheric Deposition Program (NADP) and the Moderate Resolution Imaging Spectroradiometer (MODIS) databases. We hypothesized that functional groups such as mycorrhizal fungi, saprotrophs, and pathogens would vary in their sensitivities to climate, host plant, and soil properties.
Results/Conclusions
Overall, the richness of soil fungi was correlated with Hg deposition and to a lesser extent by pH, soil C:N, and mean annual precipitation. Specifically, the richness of soil fungi declined with Hg deposition, in part, due to a one-fold decline in the richness of fungi of unknown taxonomy. By contrast, both the richness and relative abundance of ectomycorrhizal fungi was mainly predicted by soil pH followed by net primary productivity (NPP), Hg deposition and soil C availability. Interestingly, the richness and abundance of saprotrophic fungi was negatively correlated with soil C:N and soil C availability. Whereas, pH was the main predictor of the richness and relative abundance of pathogenic fungi. Surprisingly, fungi of unknown taxonomy (48% of total OTUs) were also structured strongly by Hg deposition, pH as well as C:N. Taken together, we show that complex shifts in soil fungal communities are dependent on both climate and local environmental factors, such as variation in soil biogeochemical properties. Our findings also support an emerging model that pH may play a central role in the assembly of soil fungi across terrestrial ecosystems.