Variation in Soil Microbial Communities Across Plantation Types in the Yellow River Floodplain of Western Shandong, China

The Yellow River floodplain relies on plantations for ecological restoration, yet the key factors influencing soil microbial communities remain poorly elucidated. In this study, we investigated soil microbial communities under four representative stand types (Populus tomentosa monoculture (PP), Salix matsudana monoculture (PS), Populus tomentosa-Robinia pseudoacacia mixed plantation (MPR), and Salix matsudana-Populus tomentosa mixed plantation (MSP)) in this region. Using high-throughput sequencing, we compared the soil microbial community composition and diversity across stands, and combined soil physicochemical measurements to evaluate the relationships between community variation and soil factors. The results indicated that soil physicochemical properties differed significantly among stand types, except for available phosphorus. Bacterial α-diversity was highest in MPR, whereas fungal α-diversity was highest in MSP. Variation in microbial community structure (β-diversity) was primarily explained by soil organic carbon, total nitrogen, pH, water content, and electrical conductivity, as indicated by redundancy analysis and Mantel tests. The dominant bacterial phyla were Acidobacteriota, Pseudomonadota (formerly Proteobacteria), and Actinomycetota, while the dominant fungal phyla were Ascomycota, Basidiomycota, and Mortierellomycota. These findings demonstrate significant variation in soil microbial communities among plantation types and highlight the important role of soil physicochemical properties in shaping microbial community composition.