Simulated nitrogen deposition favors stress-tolerant fungi with low potential for decomposition

Global changes such as atmospheric nitrogen (N) deposition can alter the structure of microbial communities, but a mechanistic understanding of the linkages between community structure and ecosystem function is lacking. Here we apply a trait-based framework to an analysis of litter fungal communities in a temperate forest exposed to >20 years simulated N addition in order to develop hypotheses regarding the mechanisms underlying community responses and resulting changes in ecosystem function. We performed metabarcoding of the total and active fungal communities and measured extracellular enzyme activity in leaf litter after it decomposed for approximately two years in a long-term simulated N deposition experiment. We found that N fertilization decreased the relative abundance of six species in the active community that were highly correlated with lignin decomposing enzyme activity. Four of these species have currently unknown taxonomic identity and should be targets for isolation and further characterization. Nitrogen fertilization also increased species richness and relative abundance of yeasts in the total community and decreased their relative activity levels, suggesting these species may be dormant or otherwise inactive. Together these responses may contribute to accumulation of organic matter in soils by favoring yeasts that are not strong enzyme producers and by disfavoring the fungal species that are most active in litter decomposition.