Reduction of precipitation in the region of middle latitudes and subtropics as predicted by climate models will exert significant influence on soil greenhouse gas emissions and microbial community composition, which will lead to changes in the feedback mechanism of the soil carbon and nitrogen cycle. However, response patterns of soil greenhouse gas fluxes and microbial community composition to precipitation reduction remains unclear in these forest ecosystems. We conducted a throughfall exclusion (including CT, TEF1 and TEF2, represent control, 30% throughfall exclusion and 60% throughfall exclusion, respectively) experiment in a natural Castanopsis carlesii forest of southeast China to reveal how throughfall exclusion affected greenhouse gas fluxes and microbial community. From March 2016 to February 2018, soil CO2, CH4 and N2O fluxes were measured using the static chamber-gas chromatography technique. The soil microbial community composition was determined by phospholipid fatty acid (PLFA) analysis.
Results/Conclusions
For CO2, CH4 and N2O, we observed emission and uptake ranging from 1 to 8.49 μmol CO2 m-2 h-1, -86.25 to -2.37 μg CH4 m-2 h-1 and 2.98 to 101.36 μg N2O m-2 h-1, respectively (negative values indicate uptake). Soil CO2 fluxes were correlated positively with soil temperature but not significantly correlated with soil moisture. We found no control of soil temperature or soil moisture on CH4, but N2O fluxes were positively correlated with soil moisture. In July 2017, the abundance of PLFAs of different microbial functional groups in three treatments significantly increased, and the abundance of PLFAs under TFE1 was significantly higher than that of the CT and TEF2 treatments. Interestingly, by calculating the annual cumulative flux, it was found that TEF2 with low microbial abundance of PLFAs would increase the emissions of soil CO2 and N2O, that may be related to changes in plant root growth and soil nutrient uptake strategies by varying degrees of reduced throughfall. Our study suggest that TEF1 increased the abundance of soil microbial PLFAs, but had no significant effects on soil greenhouse gas emissions. TEF2 decreased the abundance of microbial PLFAs and increased the greenhouse gas emissions to the atmosphere.