Microbial Community Composition and Major Environmental Factors Influencing Changes in Different Vegetation Soils of Coastal Wetlands

The soil microbial community in coastal wetlands plays a crucial role in biogeochemical cycling. In this study, <i>Spartina alterniflora</i> soil (HB), found near the sea; <i>Spartina alterniflora</i> soil (ZY), found near land; and <i>Phragmites australis</i> soil (KA), found in coastal wetlands, were selected to study the microbial community structure and major environmental influencing factors. The results showed that environmental factors had a significant difference in the three soils. Compared with the ZY and KA sites, the soil at the HB site had the highest value of salinity (14.1 g/kg) and the lowest value of total organic carbon (TOC) (2.9 g/kg) in summer. At the KA site, the values of soil temperature, soil humidity (SH), TOC, and NH₄⁺ were higher than those at HB and ZY sites, while the values of EC (159.8 μS/cm in summer) and salinity (4.4 g/kg) were the lowest. Furthermore, the microbial community structure had significant differences at the three sites. <i>Pseudomonas</i> and <i>Bacteroidota</i> dominated at the HB site, while <i>Chloroflexota</i> and <i>Gemmatimonades</i> were more abundant at the ZY and KA sites. Microbial alpha diversity analysis indicated that the microbial community diversity of <i>Phragmites australis</i> soil was the most uniform, and the microbial species richness in the soil of <i>Spartina alterniflora</i> near the sea was the highest. Salinity, TOC, and SH might be the key environmental factors that affect the structure and diversity of microbial communities in soils. High-salt environments may promote the enrichment of salt-tolerant microbial communities, while high TOC and suitable soil humidity may enhance the uniformity of microbial communities.