title: Scale-dependent variation in nitrogen cycling and soil fungal communities along gradients of forest composition and age in regenerating tropical dry forests.
abstract: Rates of ecosystem nitrogen (N) cycling may be mediated by the presence of ectomycorrhizal fungi, which compete directly with free-living microbes for N. In the regenerating tropical dry forests of Central America, the distribution of ectomycorrhizal trees is affected by succession and soil parent material, both of which may exert independent influence over soil N fluxes. In order to quantify these interacting controls, we used a scale-explicit sampling strategy to examine soil N cycling at scales ranging from the microsite to ecosystem level. We measured fungal community composition, total and inorganic N pools, gross proteolytic rate, net N mineralization and microbial extracellular enzyme activity at multiple locations within 18 permanent plots that span dramatic gradients of soil N concentration, stand age and forest composition. The ratio of inorganic to organic N cycling was correlated with variation in fungal community structure, consistent with a strong influence of ectomycorrhiza on ecosystem-scale N cycling. However, on average, > 61% of the variation in soil biogeochemistry occurred within plots, and the effects of forest composition were mediated by this local-scale heterogeneity in total soil N concentrations. These cross-scale interactions demonstrate the importance of a spatially explicit approach towards an understanding of controls on element cycling.
authors.affiliation: Department of Ecology, Evolution, and Behavior, University of Minnesota, St Paul, MN, 55108, USA.
authors.forename: Bonnie G
authors.initials: BG
authors.lastname: Waring
authors.affiliation: Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, CA, 94720, USA.
authors.forename: Rachel
authors.initials: R
authors.lastname: Adams
authors.affiliation: Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, CA, 94720, USA.
authors.forename: Sara
authors.initials: S
authors.lastname: Branco
authors.affiliation: Department of Ecology, Evolution, and Behavior, University of Minnesota, St Paul, MN, 55108, USA.|Department of Plant Biology, University of Minnesota, St Paul, MN, 55108, USA.
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Powers
mesh_terms: D003364:Costa Rica; D065928:Forests; D059013:Microbial Consortia / Q000235:genetics / Q000502:physiology; D038821:Mycorrhizae / Q000235:genetics; D058458:Nitrogen Cycle; D012988:Soil Microbiology; D014329:Tropical Climate
keywords: ectomycorrhizal fungi (EMF); microbial communities; nitrogen; spatial scale; tropical dry forest