Effects of flooding conditions and vegetation types on the microbial community characteristics and the abundance of denitrification functional genes in the ecotone of Lake Erhai

In order to investigate the effects of flooding conditions and vegetation types on the microbial community structure and denitrification function genes of the ecotone zone of Lake Erhai, the microorganisms present in the soil and sediment of the ecotone zone of Lake Erhai were investigated under three flooding scenarios (no-flooding area, intermittent inundation area, constant inundation area) and with six different types of vegetation cover (grassland, woodland, forest-grassland, emergent vegetation, submerged vegetation, and no vegetation). The investigation was conducted using the 16S rRNA gene high-throughput sequencing and fluorescence quantitative PCR technologies to determine changes in microbial community structure and functional gene abundance and the impact of flooding and vegetation cover on soil and sediment microbial communities in the ecotone zone of Lake Erhai. The results showed that as the area with the most frequent material exchange and energy flow in the lakeshore, the interface zone was affected by water level fluctuations, so it became a complex environmental condition. The relative abundance of important microbial groups in nitrogen cycling in this soil/sediment, such as Chloroflexi and Nitrospirota, was higher than in the land and water zone. The vegetation cover mainly affected the microbial community composition and α Diversity in the sediment in the water land. The difference in the abundance of microbial denitrification functional genes revealed the spatial distribution characteristics of denitrification microorganisms in the ecotone zone. A higher abundance of functional genes in landward and interface zones indicated a stronger microbial denitrification activity. The abundance of functional genes during the removal of nitrogen from soil or sediment in the lakeshore of Lake Erhai was affected by several key factors, including water content, carbon-to-nitrogen ratio, organic carbon, and nitrite nitrogen. The difference in the concentration of these factors was the primary cause of the variation in the abundance of functional genes for nitrogen removal under various flooding conditions and vegetation cover.