Pioneer vegetation shapes soil microbial community assembly and ecosystem functions in riparian sand mining sites

Pioneer vegetation initiates the recovery of degraded ecosystem; However, its influence on soil microbial communities in riparian sand mining sites remains poorly understood. Four naturally established pioneer plant species (Artemisia scoparia, Imperata cylindrica, Saccharum arundinaceum, and solitary trees) were selected in a representative sand mining site along the Huai River, and systematically investigated soil microbial community structure, assembly processes, co-occurrence network stability, and functional potential to elucidate the regulatory mechanisms of pioneer vegetation on soil microbial communities and ecosystem functions. The results showed that pioneer vegetation types shaped distinct soil microbial communities, with bacterial communities more responsive than fungi. Total carbon (TC), total phosphorus (TP), and nitrate nitrogen (NO₃-N) collectively explaining 76.8% of the variation in bacterial community composition. Microbial community composition exhibited strong vegetation-specific patterns. A. scoparia plots significantly enriched Actinobacteria, whereas solitary tree plots significantly enriched Basidiomycota. Network stability varied markedly with vegetation type; Functional prediction revealed that bacterial nitrogen cycling potential was significantly modulated by vegetation type, with nitrification potential being significantly lowest in I. cylindrica. Structural equation modeling demonstrated that vegetation type indirectly influenced soil multifunctionality via regulating soil physical properties, with contrasting pathways in bacterial and fungal models. Our findings suggest potential ecological mechanisms by which pioneer plants influence early ecosystem recovery in degraded riparian zones through the "plant-soil-microbe" continuum, thus providing a scientific basis for functional trait-based ecological restoration.