Effects of microtopography on soil microbial communities in alpine meadows on the Qinghai-Tibetan Plateau

Heterogeneous habitats generated by diverse microtopography are critical in shaping soil microbial communities and their ecological functions. In this study, a combination of high-throughput sequencing technology and functional prediction was used to assess the effects of three microtopographic types (the shady slope, ravine, and sunny slope) on community structure, diversity, functional guilds, and the co-occurrence networks of soil microbes in alpine meadows. The results showed that the microbial α-diversity varied significantly across the three microtopographies, and fungal community structure was more responsive to microtopography than that of bacteria. In contrast, the co-occurrence network pattern of bacteria was more sensitive to environmental changes induced by microtopography. Mantel tests revealed that bacterial community structure was mainly impacted by plant diversity, belowground biomass, soil total phosphorus content and soil pH, and variations in fungal community structure were correlated with plant diversity, soil pH, and soil NH4+–N content. Meanwhile, regression analyses indicated that nitrogen fixers, ectomycorrhizal fungi, and endophytes relative abundances were positively linked to plant diversity, and soil pH negatively affected nitrogen fixers, ectomycorrhizal fungi, and methane oxidizers. Furthermore, different functional guilds with similar functions (e.g., ectomycorrhizal fungi vs. arbuscular mycorrhizal fungi) responded inconsistently to the microtopography, suggesting ecological niche differentiation of microorganisms in microtopographies. These findings highlight the importance of microtopography for driving bacterial and fungal diversity, community structure, functional profiles and co-occurrence networks in alpine ecosystems.