Response of the nitrogen processing bacterial community to water level fluctuation and nitrate availability in an intact marsh soil column

Wetlands are known to experience fluctuations in water levels and receive exogenous nitrogen inputs that affect various organisms, including soil microorganisms. To study the impact of these factors on microbial diversity, we collected intact soil columns from a Phragmites australis -dominated site in the Qixing River National Nature Reserve in Northeast China. In a laboratory experiment, we simulated water level fluctuations and exogenous nitrogen inputs to the soil columns and examined the associated changes in the relative abundance of 51 bacterial genera involved in nitrogen cycling processes. Our findings revealed that different bacterial genera exhibited varying relative abundances across treatments. Specifically, Massilia showed the highest total relative abundance at the genus level, while Planctomyces had the second highest, and Campylobacter had the lowest abundance. The DESeq2 model, based on negative binomial distribution, revealed that the tags of bacterial genera were significantly correlated with soil depth, but not with water levels or nitrogen concentrations. However, the addition of a 30 mg/L nitrate solution caused a decrease in the relative abundances of bacterial genera with decreasing water levels, while a 60 mg/L concentration of nitrogen resulted in a decrease and then an increase in the relative abundances of bacterial genera with decreasing water levels. Our study provides valuable insights into the response of nitrogen-cycling bacteria to changes in different environmental conditions.