Emissions of biologically active N compounds have increased 300-500% over the last century, and are projected to further increase by 250% in the near future. Accumulating evidence suggests that increasing levels of atmospheric N deposition may slow the decay of plant litter, increase soil C storage, and therefore modify the biogeochemical cycling of C in soil.
Because fungi are the primary mediators of decomposition in terrestrial ecosystems, changes in the fungal community under increasing atmospheric N deposition could alter decay rates and C cycling. Our objective was to examine the effect of long-term increases in simulated atmospheric N deposition on the community composition of fungi actively metabolizing plant litter in forest floor. Our study consists of 4 replicate sugar maple (Acer saccharum) dominated northern hardwood stands which lie along a climactic gradient in the Upper Great Lakes region of the U.S. Since 1994, experimental plots in these locations have received ambient atmospheric N deposition plus simulated atmospheric N deposition at levels expected later this century (30 kg N ha-1 yr-1). Decomposition has slowed under simulated atmospheric N deposition in this long-term experiment.
Results/Conclusions
Simulated N deposition induced compositional changes in the active forest floor basidiomycete community, wherein significant differences in phylogenetic branch length occurred between basidiomycete communities under ambient and simulated N deposition (Unifrac significance; P = 0.085). Further, P-test and ∫-Libshuff indicated significant differences in basidiomycete community membership between ambient and simulated atmospheric N deposition (P test P = 0.037, ∫-Libshuff P = 0.001). More OTUs were recovered for the families Mycenaceae and Tricholomataceae under simulated N deposition. These changes may have important functional implications for understanding why rates of litter decay have slowed and forest floor mass has increased under simulated N deposition.