干旱区生态环境知识资源中心

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 watersaturated soil layer.