Soil Bacterial Community Diversity and Life Strategy during Coastal Island Slope Restoration and Forest Conversion: Changes under Aggregate Spray-Seeding Technique

Abstract Objective: The objective of this study is to address the research gap regarding the diversity and life strategies of organisms inhabiting soil environments formed by new restoration techniques such as aggregate spray-seeding (ASS), which currently remain unclear. Methods: We conducted a comparison between the ASS restoration area (SRA) and the natural vegetation area (NVA), as well as the ASS forest conversion area (FCA) and the traditional afforestation area (TAA) on Triangle Island, China. Environmental DNA sequencing was employed to analyze the diversity and life strategies of soil bacterial communities during both the summer and winter seasons. Results: The SRA and FCA showed significantly higher Chao1 index and relative abundance of r-strategy bacteria compared to NVA and TAA, along with lower DNA guanine-cytosine (GC) content. The soil bacterial communities of NVA and TAA were similar to each other, as were those of SRA and FCA. Proteobacteria and Acidobacteriota were found to be the dominant phyla in our studied soils, accounting for 67.83-76.54% of the total relative abundance. Proteobacteria had a higher relative abundance in summer, while Acidobacteriota had a higher relative abundance in winter. GC content exhibited a negative correlation (p < 0.0001) with the relative abundance of r-strategy bacteria and a positive correlation (p < 0.01) with the relative abundance of K-strategy bacteria. Conclusions: Our study demonstrates the impact of ASS application on the diversity and life strategy of soil bacterial communities, while also confirming the correlation between bacterial GC content and life strategy. These findings provide a basis for regulating soil microbial communities in ecological restoration projects.