Study on the Differentiation of Microbial Communities Under Different Soil Types in the Typical Black Soil Area of Songnen Plain

Soil type imposes multilayered environmental filtering via physical structure, chemical properties, and resource availability, shaping microbial community assembly. Using 70 samples (black soil n = 27, meadow soil n = 32, and brown soil n = 11) from a typical black soil region of the Songnen Plain, we compared brown soil (forestland) with black soil and meadow soil (cropland) via 16S rRNA V3–V4 (primers 338F/806R) and fungal (ITS1, primers ITS1F/ITS2) amplicon sequencing and physicochemical analyses. The results showed (1) significantly higher organic carbon in brown soil than in black and meadow soils (p < 0.05); (2) a systematic shift along the r–K strategy axis, with K-strategists (e.g., Mortierellomycota and Acidobacteriota) dominating in brown soil, specializing in recalcitrant organic matter decomposition and carbon sequestration, and r-strategists (e.g., Proteobacteria, Bacteroidota, and Sordariaceae) enriched in black and meadow soils, rapidly utilizing labile carbon and driving carbon release. Redundancy analysis identified total organic carbon and pH as key environmental filters driving this shift. Our findings provide an ecological-strategy perspective for understanding land-use effects on soil microbiomes, informing carbon restoration and sustainable management in black soil regions.