Rain-induced changes in soil CO(2) flux and microbial community composition in a tropical forest of China

Rain-induced soil CO(2) pulse, a rapid excitation in soil CO(2) flux after rain, is ubiquitously observed in terrestrial ecosystems, yet the underlying mechanisms in tropical forests are still not clear. We conducted a rain simulation experiment to quantify rain-induced changes in soil CO(2) flux and microbial community composition in a tropical forest. Soil CO(2) flux rapidly increased by ~83% after rains, accompanied by increases in both bacterial (~51%) and fungal (~58%) Phospholipid Fatty Acids (PLFA) biomass. However, soil CO(2) flux and microbial community in the plots without litters showed limited response to rains. Direct releases of CO(2) from litter layer only accounted for ~19% increases in soil CO(2) flux, suggesting that the leaching of dissolved organic carbon (DOC) from litter layer to the topsoil is the major cause of rain-induced soil CO(2) pulse. In addition, rain-induced changes in soil CO(2) flux and microbial PLFA biomass decreased with increasing rain sizes, but they were positively correlated with litter-leached DOC concentration rather than total DOC flux. Our findings reveal an important role of litter-leached DOC input in regulating rain-induced soil CO(2) pulses and microbial community composition, and may have significant implications for CO(2) losses from tropical forest soils under future rainfall changes.