Effects of drying-rewetting cycles on the fluxes of soil greenhouse gases

Irregular precipitation caused by climate changes has resulted in frequent events of soil drying-rewetting cycles (DWC), which can strongly affect soil carbon (C) and nitrogen (N) cycling, including the fluxes of greenhouse gases (GHGs). The response of soil carbon dioxide (CO(2)), methane (CH(4)), and nitrous oxide (N(2)O) fluxes to DWC events may differ among different ecosystem types and vary with experimental settings and soil properties, but these processes were not quantitatively assessed. Here, we evaluated the responses of soil GHG fluxes to DWC, compared with consistent moisture, as well as the associated driving factors with 424 paired observations collected from 47 publications of lab incubation experiments. Results showed that: (1) DWC significantly decreased soil CO(2) emissions by an average of 9.7%, but did not affect the emissions and uptakes of soil CH(4) and N(2)O; (2) DWC effects on soil GHG emissions varied significantly among different ecosystem types, with CO(2) emissions significantly decreased by 6.8 and 16.3% in croplands and grasslands soils, respectively, and CH(4) and N(2)O emissions significantly decreased and increased in wetlands and forests soils, respectively; (3) the effects of DWC on CO(2) emissions were also positively regulated by organic C and N concentrations, pH, clay concentration, and soil depth, but negatively by C:N ratio and silt concentration, while DWC effects on N(2)O emissions were negatively controlled by C:N ratio, silt concentration, and soil depth. Overall, our results showed that CO(2) emissions were significantly decreased by DWC, while the fluxes of CH(4) and N(2)O were not affected, indicating an overall decrease of GHGs in response to DWC. Our results will be useful for a better understanding of global GHG emissions under future climate change scenario.