title: Experimental evidence that mycorrhizal nitrogen strategies affect soil carbon.
abstract: Most land plants acquire nitrogen (N) through associations with arbuscular (AM) and ectomycorrhizal (ECM) fungi, but these symbionts employ contrasting strategies for N acquisition, which may lead to different stocks of soil carbon (C). We experimentally test this hypothesis with a mesocosm system where AM and ECM tree seedling roots, or their hyphae only, could access mineral soils with13C- and15N-enriched organic matter. We quantified loss of soil C and N, plant uptake of N and new inputs of plant C to soil. We found that AM, but not ECM, seedlings reduced soil C relative to controls. Soil C loss was greater in the presence of roots relative to hyphae only for both AM and ECM seedlings, but was correlated with plant N uptake for AM seedlings only. While new plant C inputs stimulated soil C loss in both symbioses, we detected plant C inputs more frequently and measured higher rates of decomposer activity in soils colonized by AM relative to ECM seedlings. Our study experimentally demonstrates how mycorrhizal strategies for N can affect soil C and C:N, even at the scale of an individual plant. Such effects may contribute to broad patterns in soil C across terrestrial ecosystems.
authors.affiliation: Odum School of Ecology, University of Georgia, 140 East Green Street, Athens, Georgia, 30602, USA.
authors.forename: Nina
authors.initials: N
authors.lastname: Wurzburger
authors.affiliation: Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, Montana, 59717, USA.
authors.forename: E N Jack
authors.initials: ENJ
authors.lastname: Brookshire
mesh_terms: D002244:Carbon / Q000032:analysis / Q000378:metabolism*; D038821:Mycorrhizae / Q000502:physiology*; D009584:Nitrogen / Q000378:metabolism*; D018517:Plant Roots; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology
chemical_list: D012987:Soil; D002244:Carbon; D009584:Nitrogen
keywords: arbuscular mycorrhizal fungi; carbon; decomposition; ecosystem biogeochemistry; ectomycorrhizal fungi; nitrogen; soil organic matter