title: Microbial denitrification dominates nitrate losses from forest ecosystems.
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.
authors.affiliation: 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;
authors.forename: Yunting
authors.initials: Y
authors.lastname: Fang
authors.affiliation: Institute of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 1838509, Japan; keikoba@cc.tuat.ac.jp.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Koba
authors.affiliation: Institute of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 1838509, Japan;
authors.forename: Akiko
authors.initials: A
authors.lastname: Makabe
authors.affiliation: Institute of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 1838509, Japan;
authors.forename: Chieko
authors.initials: C
authors.lastname: Takahashi
authors.affiliation: Department of Biological Sciences, Binghamton University, The State University of New York, Binghamton, NY 13902;
authors.forename: Weixing
authors.initials: W
authors.lastname: Zhu
authors.affiliation: Institute of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 1838509, Japan;
authors.forename: Takahiro
authors.initials: T
authors.lastname: Hayashi
authors.affiliation: Institute of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 1838509, Japan;
authors.forename: Azusa A
authors.initials: AA
authors.lastname: Hokari
authors.affiliation: Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 1138657, Japan;
authors.forename: Rieko
authors.initials: R
authors.lastname: Urakawa
authors.affiliation: State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110164, China;
authors.forename: Edith
authors.initials: E
authors.lastname: Bai
authors.affiliation: Department of Land, Air, and Water Resources, University of California, Davis, CA 95616;
authors.forename: Benjamin Z
authors.initials: BZ
authors.lastname: Houlton
authors.affiliation: State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110164, China;
authors.forename: Dan
authors.initials: D
authors.lastname: Xi
authors.affiliation: State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110164, China;
authors.forename: Shasha
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Institute of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 1838509, Japan;
authors.forename: Kayo
authors.initials: K
authors.lastname: Matsushita
authors.affiliation: State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110164, China;
authors.forename: Ying
authors.initials: Y
authors.lastname: Tu
authors.affiliation: State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110164, China;
authors.forename: Dongwei
authors.initials: D
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110164, China;
authors.forename: Feifei
authors.initials: F
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110164, China;
authors.forename: Zhenyu
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China;
authors.forename: Guoyi
authors.initials: G
authors.lastname: Zhou
authors.affiliation: Research Institute of Tropical Forestry, Chinese Academy of Forestry, Guangzhou 510520, China; and.
authors.forename: Dexiang
authors.initials: D
authors.lastname: Chen
authors.affiliation: Institute of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 1838509, Japan;
authors.forename: Tomoko
authors.initials: T
authors.lastname: Makita
authors.affiliation: Institute of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 1838509, Japan;
authors.forename: Hiroto
authors.initials: H
authors.lastname: Toda
authors.affiliation: Institute of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 1838509, Japan;
authors.forename: Xueyan
authors.initials: X
authors.lastname: Liu
authors.affiliation: 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.
authors.forename: Quansheng
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China;
authors.forename: Deqiang
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Research Institute of Tropical Forestry, Chinese Academy of Forestry, Guangzhou 510520, China; and.
authors.forename: Yide
authors.initials: Y
authors.lastname: Li
authors.affiliation: Institute of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 1838509, Japan;
authors.forename: Muneoki
authors.initials: M
authors.lastname: Yoh
mesh_terms: D058440:Denitrification; D017753:Ecosystem; D065928:Forests; D064307:Microbiota; D009566:Nitrates / Q000378:metabolism*
chemical_list: D009566:Nitrates
keywords: denitrification; forested watersheds; nitrate isotopes; nitrogen cycling