title: Convergence of soil nitrogen isotopes across global climate gradients.
abstract: Quantifying global patterns of terrestrial nitrogen (N) cycling is central to predicting future patterns of primary productivity, carbon sequestration, nutrient fluxes to aquatic systems, and climate forcing. With limited direct measures of soil N cycling at the global scale, syntheses of the (15)N:(14)N ratio of soil organic matter across climate gradients provide key insights into understanding global patterns of N cycling. In synthesizing data from over 6000 soil samples, we show strong global relationships among soil N isotopes, mean annual temperature (MAT), mean annual precipitation (MAP), and the concentrations of organic carbon and clay in soil. In both hot ecosystems and dry ecosystems, soil organic matter was more enriched in (15)N than in corresponding cold ecosystems or wet ecosystems. Below a MAT of 9.8°C, soil δ(15)N was invariant with MAT. At the global scale, soil organic C concentrations also declined with increasing MAT and decreasing MAP. After standardizing for variation among mineral soils in soil C and clay concentrations, soil δ(15)N showed no consistent trends across global climate and latitudinal gradients. Our analyses could place new constraints on interpretations of patterns of ecosystem N cycling and global budgets of gaseous N loss.
authors: Division of Biology, Kansas State University, Manhattan, KS, 66506, USA.
authors: Joseph M
authors: JM
authors: Craine
authors: Appalachian Laboratory, University of Maryland Center for Environmental Science, Frostburg, MD, 21532, USA.
authors: Andrew J
authors: AJ
authors: Elmore
authors: Department of Earth Sciences, Indiana University-Purdue University, Indianapolis, IN, 46202, USA.
authors: Lixin
authors: L
authors: Wang
authors: UMR 1220 TCEM, INRA, Bordeaux Sciences Agro, Villenave d'Ornon, 33883, France.
authors: Laurent
authors: L
authors: Augusto
authors: National Isotope Centre, GNS Science, Lower Hutt, 5040, New Zealand.
authors: W Troy
authors: WT
authors: Baisden
authors: Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, 59717, USA.
authors: E N J
authors: EN
authors: Brookshire
authors: Department of Biological Sciences, University of Cape Town, Rondebosch, 7701, South Africa.
authors: Michael D
authors: MD
authors: Cramer
authors: Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Umeå, 90183, Sweden.
authors: Niles J
authors: NJ
authors: Hasselquist
authors: Earth Systems Research Center, Morse Hall, University of New Hampshire, Durham, NH, 03824, USA.
authors: Erik A
authors: EA
authors: Hobbie
authors: Departement of Environmental Sciences - Botany, Schönbeinstrasse 6, 4056 Basel Switzerland.
authors: Ansgar
authors: A
authors: Kahmen
authors: Institute of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo, 1838509, JAPAN.
authors: Keisuke
authors: K
authors: Koba
authors: British Columbia Ministry of Forests, Lands and Natural Resource Operations, Victoria, British Columbia, V8Z 5J3, Canada.
authors: J Marty
authors: JM
authors: Kranabetter
authors: Department of Biology, University of Florida, Gainesville, FL, 32607, USA.
authors: Michelle C
authors: MC
authors: Mack
authors: Department of Geography, University of Wisconsin, Madison, WI, 53706, USA.
authors: Erika
authors: E
authors: Marin-Spiotta
authors: Department of Forest Ecology &Management, Swedish University of Agricultural Sciences, Umeå 901 83, Sweden.
authors: Jordan R
authors: JR
authors: Mayor
authors: Department of Geography, Kansas State University, Manhattan, KS, 66506, USA.
authors: Kendra K
authors: KK
authors: McLauchlan
authors: Department of Biology, University of Copenhagen, Copenhagen Ø, 2100, Denmark.
authors: Anders
authors: A
authors: Michelsen
authors: Faculdade UnB Planaltina, Universidade de Brasília, Brasília, 73345-010, Brazil.
authors: Gabriela B
authors: GB
authors: Nardoto
authors: Departamento de Biologia Vegetal, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, 13083-862, Brazil.
authors: Rafael S
authors: RS
authors: Oliveira
authors: Forest and Rangeland Ecosystem Science Center, US Geological Survey, Corvallis, OR, 97331, USA.
authors: Steven S
authors: SS
authors: Perakis
authors: Universidad Nacional de la Patagonia Austral-INTA-CONICET, Río Gallegos, Santa Cruz, 9400, Argentina.
authors: Pablo L
authors: PL
authors: Peri
authors: Coordenação de Dinâmica Ambiental, Instituto Nacional de Pesquisas da Amazonia, Manaus, 69011, Brazil.
authors: Carlos A
authors: CA
authors: Quesada
authors: Department of Terrestrial Ecosystem Research, University of Vienna, Vienna, 1090, Austria.
authors: Andreas
authors: A
authors: Richter
authors: Environmental Research Institute, University of Waikato, Hamilton, 3240, New Zealand.
authors: Louis A
authors: LA
authors: Schipper
authors: Landcare Research, Hamilton, 3240, New Zealand.
authors: Bryan A
authors: BA
authors: Stevenson
authors: Smithsonian Tropical Research Institute, Balboa, Ancón, Republic of Panama.
authors: Benjamin L
authors: BL
authors: Turner
authors: DBPVA, Centro de Ciências Agrárias, Universidade Federal de São Carlos, Araras, SP, 13600-970, Brazil.
authors: Ricardo A G
authors: RA
authors: Viani
authors: Department of Terrestrial Ecosystem Research, University of Vienna, Vienna, 1090, Austria.
authors: Wolfgang
authors: W
authors: Wanek
authors: Biogéochimie des Ecosystèmes Forestiers, INRA Nancy, Champenoux, 54280, France.
authors: Bernd
authors: B
authors: Zeller
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