Applicability of the soil gradient method for estimating soil–atmosphere CO2, CH4, and N2O fluxes for steppe soils in Inner Mongolia |
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| Authors: | Benjamin Wolf Weiwei Chen Nicolas Brüggemann Xunhua Zheng Jukka Pumpanen Klaus Butterbach‐Bahl |
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| Institution: | 1. Institute for Meteorology and Climate Research (IMK‐IFU), Karlsruhe Institute of Technology, Kreuzeckbahnstra?e 19, 82467 Garmisch‐Partenkirchen, Germany;2. State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute for Atmospheric Physics, Chinese Academy of Sciences (IAP‐CAS), 100029 Beijing, China;3. Department of Forest Ecology, P.O. Box 27, FI‐00014 University of Helsinki, Finland |
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| Abstract: | For evaluating the applicability of the soil gradient method as a substitute for CO2‐, CH4‐, and N2O‐flux measurements in steppe, we carried out chamber measurements and determined soil gas concentration at an ungrazed (UG99) and a grazed (WG) site in Inner Mongolia, China. The agreement of the concentration‐based flux estimates with measured chamber‐based fluxes varied largely depending on the respective GHG in the sequence CO2 > CH4 >> N2O. A calibration of the gas‐transport parameter used to calculate fluxes based on soil gas concentrations improved the results considerably for CO2 and CH4. After calibration, the average deviation from the chamber‐based annual cumulative flux for both sites was 11.5%, 10.5%, and 59% for CO2, CH4, and N2O. The gradient method did not constitute an adequate stand‐alone substitute for greenhouse‐gas flux estimation since a calibration using chamber‐based measurements was necessary and vigorous production processes were confined to the uppermost, almost water‐saturated soil layer. |
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| Keywords: | GHG exchange diffusion gas‐concentration gradient grassland |
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