Responses of soil C pools to combined warming and altered precipitation regimes: A meta‐analysis

Abstract Aim Global warming and altered precipitation substantially affect soil carbon (C) pools and can, in turn, feed back into climate change. However, how soil C pools respond to the combined effects of warming and altered precipitation remains unclear. Location Global. Time period 1996–2021. Major taxa studied Soil organic C pools. Method A meta‐analysis was performed using 657 observations obtained from 34 published articles that focused on both individual and combined effects of warming and altered precipitation on soil organic C (SOC), dissolved organic C (DOC) and microbial biomass C (MBC) to quantify the responses of soil C pools. Results Across all combined warming and increased precipitation experiments, SOC and MBC increased by an average of 4.0% and 15.4%, respectively. In contrast, warming combined with decreased precipitation led to a substantial decline in SOC and MBC by an average of 8.2% and 12.3%, respectively. The responses of DOC to combined warming and altered precipitation were marginal. The direction and magnitude of the responses to the combined treatment were more similar to those in the individual altered precipitation treatment than to those in the individual warming treatment. Furthermore, these combined effects were substantially influenced by altered precipitation magnitudes. Combined warming and altered precipitation had greater impacts on soil C pools than their individual treatments but were not substantially different from the sum of their respective individual effects, showing overall additive effects. The responses of soil C pools to combined warming and altered precipitation were observed to be more pronounced in grasslands than in forests. Main conclusion The results demonstrated that altered precipitation regimes often dominated over warming in regulating soil C pools under combined warming and altered precipitation and improved our understanding of soil C cycles under climate change scenarios.