Responses of soil microbial biomass carbon and dissolved organic carbon to drying-rewetting cycles: A meta-analysis

Climate change may significantly increase drying-wetting cycles (DWC) in terrestrial ecosystems. However, the effects of DWC on soil microbial biomass carbon (MBC) and dissolved organic carbon (DOC) remain elusive. Therefore, we used a meta-analysis including 187 observations to clarify the effects of DWC on soil MBC and DOC. The results showed that DWC increased soil MBC by 9.5%. The effect size was negatively related to soil clay content, SOC, total nitrogen, while it was positively related to soil sampling depth, and the ratio of drying days over the total number of days in a DWC (D/T). Simultaneously, DWC increased soil DOC by 12.3%. Moreover, the effect size of MBC continuously increased with the number of DWC, while that of DOC decreased with the number of DWC. This result may explain why the CO2 pulse after rewetting continues, but its amplitude decreases gradually with the increase of DWC number. Overall, our results help understand the responses of soil MBC and DOC to DWC in terrestrial ecosystems, and could improve the prediction of soil carbon emissions under more variable soil moisture regimes in the future.