It has been well acknowledged that a continuous increase in atmospheric carbon dioxide (CO 2 ) concentration will lead to climate warming. Numerous experiments have found that increased precipitation could promote soil CO 2 emissions into the atmosphere, but there is great uncertainty in the magnitude of increased precipitation of this feedback. Here, we assessed the influences of different durations and magnitudes of increased precipitation on soil CO 2 efflux across biomes through a meta-analysis. Humid (extremely wet, moderately wet, and slightly wet), temperate, and arid (slight drought, moderate drought and extreme drought) areas were classified ac cording to the Palmer drought severity index (PDSI). Overall, the average experimentally applied precipitation increases of 31.81%, 19.14% and 37.68% significantly stimulated soil CO 2 efflux by 12.74%, 13.10% and 14.71%, respectively for experiments from all areas, humid areas, and arid areas. No significant effects were found for temperate areas. Increased precipitation stimulated large soil CO 2 efflux in extreme drought areas (PDSI > − 3) by 38.09%. Moreover, soil CO 2 efflux increased with increasing precipitation intensity but decreased with increasing precipitation duration regardless of the area with different PDSIs. Our results highlight the positive feedback between soil CO 2 efflux and increased precipitation in both humid and arid terrestrial ecosystems, which improves our understanding in possible climate change effects on the global carbon cycle. Further efforts should assess the differential effects of various durations and magnitudes of increased precipi tation in ecosystems with different wetness conditions.

Climate change,Greenhouse gas,Carbon cycle,Arid areas,Humid areas