Arbuscular mycorrhizal fungi affect the response of soil CO 2 emission to summer precipitation pulse following drought in rooted soils

Drought and extreme precipitation are projected to occur more frequently as a consequence of climate change, with uncertain implications for soil CO 2 emission. Although studies have revealed the response patterns of soil CO 2 emission to precipitation pulse, the effects of forest plant roots on this relationship after drought are still poorly understood. Here, a field experiment was performed to examine the differences in soil CO 2 emission and microbial community between rootless and rooted soils, pretreated with three drought intensities (control, moderate, and severe), and rewetted with different water additions (0, 5, 10, and 20 mm) in a temperate forest. Compared with control soils, whether the water was added or not, severe drought suppressed soil CO 2 emission for both root-excluded and -included soils. Regardless of drought intensities, significantly positive effects (19.4 - 44.9%) of precipitation pulse on soil CO 2 emission were only detected in the root-included soils. Both the contribution of root-derived CO 2 to the stimulated soil CO 2 emission and biomass of soil arbuscular mycorrhizal fungi (AMF) substantially increased with elevated precipitation levels. The enhanced soil CO 2 emission following precipitation pulse is primarily due to the increase in root-derived CO 2 in the rooted soils, likely resulting from the enhanced biomass of soil AMF. This study provides empirical evidence on the primacy of AMF in root-derived CO 2 and thus the response of soil CO 2 emission to precipitation pulse in forest ecosystems.