Denitrification as a major regional nitrogen sink in subtropical forest catchments : Evidence from multi-site dual nitrate isotopes
© 2019 John Wiley & Sons Ltd.
| Veröffentlicht in: | Global change biology. - 1999. - 25(2019), 5 vom: 15. Mai, Seite 1765-1778 |
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| 1. Verfasser: | |
| Weitere Verfasser: | , , , , |
| Format: | Online-Aufsatz |
| Sprache: | English |
| Veröffentlicht: |
2019
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| Zugriff auf das übergeordnete Werk: | Global change biology |
| Schlagworte: | Journal Article Research Support, Non-U.S. Gov't groundwater discharge zone hydrological continuum isotopic modelling nitrification nitrogen removal δ15N and δ18O of nitrate Nitrates Nitrogen |
| Zusammenfassung: | © 2019 John Wiley & Sons Ltd. Increasing nitrogen (N) deposition in subtropical forests in south China causes N saturation, associated with significant nitrate (NO3- ) leaching. Strong N attenuation may occur in groundwater discharge zones hydrologically connected to well-drained hillslopes, as has been shown for the subtropical headwater catchment "TieShanPing", where dual NO3- isotopes indicated that groundwater discharge zones act as an important N sink and hotspot for denitrification. Here, we present a regional study reporting inorganic N fluxes over two years together with dual NO3- isotope signatures obtained in two summer campaigns from seven forested catchments in China, representing a gradient in climate and atmospheric N input. In all catchments, fluxes of dissolved inorganic N indicated efficient conversion of NH4+ to NO3- on well-drained hillslopes, and subsequent interflow of NO3- over the argic B-horizons to groundwater discharge zones. Depletion of 15 N- and 18 O-NO3- on hillslopes suggested nitrification as the main source of NO3- . In all catchments, except one of the northern sites, which had low N deposition rates, NO3- attenuation by denitrification occurred in groundwater discharge zones, as indicated by simultaneous 15 N and 18 O enrichment in residual NO3- . By contrast to the southern sites, the northern catchments lack continuous and well-developed groundwater discharge zones, explaining less efficient N removal. Using a model based on 15 NO3- signatures, we estimated denitrification fluxes from 2.4 to 21.7 kg N ha-1 year-1 for the southern sites, accounting for more than half of the observed N removal. Across the southern catchments, estimated denitrification scaled proportionally with N deposition. Together, this indicates that N removal by denitrification is an important component of the N budget of southern Chinese forests and that natural NO3- attenuation may increase with increasing N input, thus partly counteracting further aggravation of N contamination of surface waters in the region |
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| Beschreibung: | Date Completed 10.06.2019 Date Revised 13.06.2019 published: Print-Electronic Citation Status MEDLINE |
| ISSN: | 1365-2486 |
| DOI: | 10.1111/gcb.14596 |