Response of Soil Microbial Communities to Environmental Conditions in Paulownia and Coniferous Mixed Forests

The regulation of soil microbial communities by tree species composition in afforestation is crucial, particularly in resource-limited environments. This study employed substrate-induced respiration (SIR) and phospholipid fatty acid (PLFA) analyses to compare the effects of pure stands of Paulownia spp., Pinus massoniana, Cunninghamia lanceolata, and mixed stands of Paulownia with these two coniferous species on soil microbial community function and structure under two contrasting nutrient conditions: relatively fertile brown soil and poor sandy ginger black soil. Results indicated that the impact of stand type on microorganisms was significantly dependent on habitat conditions. In the nutrient-poor habitat, compared to pure Paulownia stands, both pure conifer stands and their mixed stands with Paulownia significantly decreased microbial basal respiration and biomass, and increased physiological stress indicators, with pure C. lanceolata stands exhibiting the most pronounced inhibitory effect. In contrast, microbial specific respiration and stress indicators under pure Paulownia stands showed less fluctuation across different habitats. Soil depth was also a key factor, with microbial activity and biomass decreasing with depth, and the impact patterns of stand type and habitat varying across soil layers. Microbial community structure was predominantly driven by habitat type, although stand type also exerted significant regulatory effects (especially in the litter layer and topsoil), an independent effect подарки even after controlling for soil physicochemical covariates. This study reveals that in low-nutrient regions, inappropriate conifer planting may impair soil microbial-mediated ecological functions, whereas in high-nutrient environments, the influence of tree species selection is relatively limited. Root-derived carbon input is considered an important mechanism mãe microbial responses. The impact of artificial forest stand composition on soil microorganisms necessitates a comprehensive assessment considering site-specific resource availability and soil vertical differentiation.