Bacterial community composition in soils covered by different vegetation types in the Yancheng tidal marsh

Coastal wetland vegetation plays an important role in maintaining ecological function and is a key factor affecting the soil bacterial community. Spartina alterniflora was introduced to the Yancheng tidal marsh to stabilize the sediments and gradually replaced the native plants. However, the changes in the soil bacterial community profile caused by S. alterniflora invasion are poorly characterized. Here, we used MiSeq sequencing to compare the composition of the bacterial community in soil at different depths under exotic S. alterniflora (SA), native Phragmites australis (PA), and native Suaeda salsa (SS). The results showed that the pH value was lower, but the salinity, soil organic carbon, total nitrogen, and number of 16S rRNA genes were higher in SA soils than in PA and SS soils. Overall, Proteobacteria was the dominant bacterial phylum, followed by Chloroflexi, Acidobacteria, Planctomycetes, Gemmatimonadetes, and Nitrospirae. Anaerolineae in the Chloroflexi phylum showed the greatest difference based on vegetation, accounting for 14.4% of the overall bacterial community in SA soils but only about 3.8% of those in PA and SS soils. The composition, interaction, and predicted functional profiles of the bacterial community in SA soils were significantly different from those in PA and SS soils, especially for functions related to the sulfur and nitrogen cycles. Salinity was negatively correlated with the Shannon index and accounted for 37.7% of the total variation in the bacterial community, making it the most important environmental factor. Our results showed the differences in bacterial community composition among different vegetation types and soil depths in the Yancheng tidal marsh, which provides a microbial basis for a better understanding of the ecological functions in this ecosystem.