Sinks for nitrogen inputs in terrestrial ecosystems: a meta-analysis of 15N tracer field studies

Templer Pamela H. 1, Mack Michelle C. 2, Chapin F. Stuart III 3, Christenson Lynn M. 4, Compton Jana D. 5, Crook Hannah D. 6, Currie William S. 7, Curtis Christopher J. 8, Dail D. Bryan 9, D'Antonio Carla M. 10, Emmett Bridget A. 11, Hepstein Howie E. 12, Goodale Christine L. 13, Gundersen Per 14, Hobbie Sarah E. 15, Holland Keri 16, Hooper David U. 17, Hungate Bruce A. 18, Lamontagne S├ębastien 19, Nadelhoffer Knute J. 20, Osenberg Craig W. 2, Perakis Steven S. 21, Schleppi Patrick 22, Schimel Joshua 10, Schmidt Inge K. 14, Sommerkorn Martin 23, Spoelstra John 24,25, Tietema Albert 26, Wessel Wim W. 26, Zak Donald R. 7,20

1 Department of Biology, Boston University, 5 Cummington Street, Boston, MA 02215, USA
2 Department of Biology, University of Florida, Gainesville, FL 32611-8525, USA
3 Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
4 Department of Biology, Vassar College, 124 Raymond Avenue, Poughkeepsie, NY 12604, USA
5 US Environmental Protection Agency, ORD-NHEERL-WED, 200 SW 35th St., Corvallis, OR 97333, USA
6 Natural Environment Research Council, Polaris House, Swindon, SN2 1EU, UK
7 School of Natural Resources and Environment, University of Michigan, 440 Church Street, Ann Arbor, MI 48109, USA
8 Environmental Change Research Centre, Geography Department, Pearson Building, University. College London, Gower Street, London WC1E 6BT, UK
9 Department of Plant, Soil and Environmental Sciences, University of Maine, Orono, ME 04469, USA
10 Department of Ecology, Evolution and Marine Biology. University of California, Santa Barbara. Santa Barbara, CA 93106-9620, USA
11 Centre for Ecology and Hydrology, Environment Centre Wales, Deiniol Rd, Bangor, Gwynedd, LL57 2UW, UK
12 Dept. of Environmental Sciences, University of Virginia, P.O. Box 400123 Charlottesville, VA 22904-4123, USA
13 Department of Ecology and Evolutionary Biology, Cornell University, E215 Corson Hall, Ithaca, NY 14853, USA
14 Forest and Landscape Denmark, University of Copenhagen, Rolighedsvej 23 DK-1958 Frederiksberg C, Denmark
15 Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN, 55108, USA
16 Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA
17 Department of Biology, Western Washington University, Bellingham, WA 98225-9160, USA
18 Department of Biological Sciences and Merriam-Powell Center for Environmental Research, Northern Arizona University, Flagstaff AZ 86011, USA
19 CSIRO Land and Water, Waite Campus, PMB 2 Glen Osmond SA 5064, Australia
20 Department of Ecology and Evolutionary Biology, University of Michigan, 830 North University Avenue, Ann Arbor, MI 48109-1048, USA
21 US Geological Survey, Forest and Rangeland Ecosystem Science Center, Corvallis, OR 97331, USA
22 Swiss Federal Institute for Forest, Snow and Landscape Research, Z├╝rcherstr. 111, CH-8903 Birmensdorf, Switzerland
23 World Wildlife Fund Global Arctic Programme, P.O. Box 6784, St. Olavs Plass, NO-0130 Oslo, Norway
24 Groundwater Quality and Assessment Section, National Water Research Institute, Environment Canada, 867 Lakeshore Road, P.O. Box 5050, Burlington, ON, L7R 4A6, Canada
25 Department of Earth and Environmental Sciences, University of Waterloo, 200 University Ave. W., Waterloo, ON, N2L 3G1, Canada
26 Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, PO Box 94240, NL-1090 GE Amsterdam, The Netherlands

Ecology 93 (2012): 1816-1829

DOI: 10.1890/11-1146.1


Abstract

Effects of anthropogenic nitrogen (N) deposition and the ability of terrestrial ecosystems to store carbon (C) depend in part on the amount of N retained in the system and its partitioning among plant and soil pools. We conducted a meta-analysis of studies at 48 sites across four continents that used enriched 15N isotope tracers in order to synthesize information about total ecosystem N retention (i.e. total ecosystem 15N recovery in plant and soil pools) across natural systems and N partitioning among ecosystem pools. The greatest ecosystem tracer 15N recoveries occurred in shrublands (mean = 89.5%) and wetlands (84.8%) followed by forests (74.9%) and grasslands (51.8%). In the short-term (<1 week after 15N tracer application), total ecosystem 15N recovery was negatively correlated with fine root and soil 15N natural abundance, and organic soil C and N concentration, but was positively correlated with mean annual temperature and mineral soil C:N. In the longer-term (3 to 18 months after 15N tracer application), total ecosystem 15N retention was negatively correlated with foliar natural abundance 15N, but was positively correlated with mineral soil C and N concentration and C:N, showing that plant and soil natural abundance 15N and soil C:N are good indicators of total ecosystem N retention. Foliar N concentration was not significantly related to ecosystem 15N tracer recovery, suggesting that plant N status is not a good predictor of total ecosystem N retention. Because the largest ecosystem sinks for tracer 15N were belowground in forests, shrublands, and grasslands, we conclude that growth enhancement and potential for increased C storage in aboveground biomass from atmospheric N deposition is likely to be modest in these ecosystems. Total ecosystem 15N recovery decreased with N fertilization, with an apparent threshold fertilization rate of 46 kg N ha-1 yr-1 above which most ecosystems showed net losses of applied tracer 15N in response to N fertilizer addition.

Keywords: atmospheric nitrogen deposition, carbon storage, data synthesis, meta-analysis, nitrogen retention and loss, stable isotopes


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