Effects of warming and precipitation changes on soil GHG fluxes: A meta-analysis.

Increased atmospheric greenhouse gas (GHG) concentrations resulting from human activities lead to climate change, including global warming and changes of precipitation patterns worldwide, which in turn would have profound effects on soil GHG emissions. Nonetheless, the impact of the combination of warming and precipitation changes on all three major biogenic GHGs (CO, CH and NO) has not been synthesized, to build a global synthesis. In this study, we conducted a global meta-analysis concerning the effects of warming and precipitation changes and their interactions on soil GHG fluxes and explored the potential factors by synthesizing 39 published studies worldwide. Across all studies, combination of warming and increased precipitation showed more significant effect on CO emissions (24.0%) than the individual effect of warming (8.6%) and increased precipitation (20.8%). Additionally, warming increased NO emissions (28.3%), and decreased precipitation reduced CO (-8.5%) and NO (-7.1%) emissions, while the combination of warming and decreased precipitation also showed negative effects on CO (-7.6%) and NO (-14.6%) emissions. The interactive effects of warming and precipitation changes on CO emissions were usually additive, whereas CO and NO emissions were dominated by synergistic effects under warming and decreased precipitation. Moreover, climate, biome, duration, and season of manipulations also affected soil GHG fluxes as well. Furthermore, we also found the threshold effects of changes in soil temperature and moisture on CO and NO emissions under warming and precipitation changes. The findings indicate that both warming and precipitation changes substantially affect GHG emissions and highlight the urgent need to study the effect of the combination of warming and precipitation changes on C and N cycling under ongoing climate change.