OOS 40-8 - Elevated atmospheric N deposition alters composition of forest floor fungal communities

Thursday, August 11, 2011: 4:00 PM
17A, Austin Convention Center
Elizabeth M. Entwistle, School of Natural Resources, University of Michigan, Ann Arbor, MI and Donald R. Zak, School of Natural Resources & Environment, University of Michigan, Ann Arbor, MI

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. 


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.

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