LAUSR

Abstract In China, most riparian wetlands have undergone degradation and shrinkage, due to severe droughts or low hydrological connectivity. There are considerable studies focusing on the impact of water level on wetland vegetation; however, changes in the soil components, such as the microbial community, of wetlands following flooding remains unclear. Here, we verified the effects of an extreme flooding event on the soil physicochemical conditions, enzyme activities and soil microbial composition. Overall, we observed that the flooding event impacted the soil properties and modified the enzyme activities. Also, the flooding affected more the biomass than the composition of the soil microbial community. We observed that after the flooding event, manganese (Mn) replaced total nitrogen (TN) as one of the major governing factors of soil enzyme activities. Soil organic carbon (SOC), and pH were also correlated with soil enzyme activities before and after the flooding event. Soil conductivity (EC), C/N ratio, and iron (Fe) contents had a large influence on microbial communities. Nevertheless, the soil C/N ratio was the dominant governing factor of the microbial structure. Therefore, edaphic factors were remarkably related to microbial organisms as flooding was deemed a key driving factor to the linkage between them. The antecedent long-term drought provoked by human disturbance, and subsequent flooding (i.e., re-inundating) may thus damage the soil dynamics of riparian wetlands, and hence, altering the carbon storage capacity. The results of this study suggest that rehabilitating hydrological connectivity and promoting primary succession of vegetation could become effective practices for improving the soil ecosystem of riparian wetlands.