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Proc Natl Acad Sci U S A. 2015 Feb 3;112(5):1470-4. doi: 10.1073/pnas.1416776112. Epub 2015 Jan 20.

Microbial denitrification dominates nitrate losses from forest ecosystems.

Author information

1
State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110164, China; Institute of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 1838509, Japan;
2
Institute of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 1838509, Japan; keikoba@cc.tuat.ac.jp.
3
Institute of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 1838509, Japan;
4
Department of Biological Sciences, Binghamton University, The State University of New York, Binghamton, NY 13902;
5
Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 1138657, Japan;
6
State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110164, China;
7
Department of Land, Air, and Water Resources, University of California, Davis, CA 95616;
8
Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China;
9
Research Institute of Tropical Forestry, Chinese Academy of Forestry, Guangzhou 510520, China; and.
10
State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110164, China; State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.

Abstract

Denitrification removes fixed nitrogen (N) from the biosphere, thereby restricting the availability of this key limiting nutrient for terrestrial plant productivity. This microbially driven process has been exceedingly difficult to measure, however, given the large background of nitrogen gas (N2) in the atmosphere and vexing scaling issues associated with heterogeneous soil systems. Here, we use natural abundance of N and oxygen isotopes in nitrate (NO3 (-)) to examine dentrification rates across six forest sites in southern China and central Japan, which span temperate to tropical climates, as well as various stand ages and N deposition regimes. Our multiple stable isotope approach across soil to watershed scales shows that traditional techniques underestimate terrestrial denitrification fluxes by up to 98%, with annual losses of 5.6-30.1 kg of N per hectare via this gaseous pathway. These N export fluxes are up to sixfold higher than NO3 (-) leaching, pointing to widespread dominance of denitrification in removing NO3 (-) from forest ecosystems across a range of conditions. Further, we report that the loss of NO3 (-) to denitrification decreased in comparison to leaching pathways in sites with the highest rates of anthropogenic N deposition.

KEYWORDS:

denitrification; forested watersheds; nitrate isotopes; nitrogen cycling

PMID:
25605898
PMCID:
PMC4321283
DOI:
10.1073/pnas.1416776112
[Indexed for MEDLINE]
Free PMC Article

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