Seasonal variations in rhizosphere soil bacterial and fungal communities of Quercus franchetii along an elevational gradient in the Yuanmou dry-hot valley, Southwest China

Background Soil microbial communities are essential components and key drivers in maintaining ecosystem function. This study focused on Quercus franchetii in the Yuanmou dry-hot valley of Southwest China, and analyzed the characteristics of rhizosphere soil microbial communities along an elevational gradient in the dry and rainy season using high-throughput sequencing technique. Result Actinobacteriota, Proteobacteria, Acidobacteriota, and Chloroflexi were identified as the dominant bacterial phyla, with Acidothermus , Conexibacter , Mycobacterium , and Bryobacter as the dominant genera. For fungi, Ascomycota and Basidiomycota were identified as the dominant phyla, with Russula , Penicillium , Phialomyces , and Sebacina as the most abundant genera. Elevation was a more important determinant of bacterial α-diversity than season. By contrast, fungal α-diversity was significantly affected by season but not by elevation. Elevation significantly shaped the community structure of both bacteria and fungi. Soil pH was the primary driver of bacterial α-diversity, whereas fungal α-diversity correlated with none of the measured soil physicochemical properties. Soil pH and water content exerted highly significant effects on bacterial community structure, whereas only soil pH had a highly significant impact on fungal community structure. The bacteria-fungi co-occurrence network in the dry season featured a higher proportion of positive correlations. The functions of the bacterial community were primarily chemoheterotrophic and aerobic chemoheterotrophic, with significant seasonal differences in cellulolysis, nitrate reduction, and ureolysis. Symbiotroph and saprotroph‑symbiotroph, pathotroph‑saprotroph were the dominant trophic modes in the fungal community, with significant seasonal differences in ectomycorrhizal fungi and saprotrophic fungi. Conclusions Bacterial community diversity showed higher sensitivity to environmental fluctuations, while fungal diversity exhibited more pronounced seasonal variation. Soil pH was the primary driver of bacterial and fungal diversity. Bacterial functions were dominated by carbon cycling processes, with seasonal differences in cellulolysis, nitrate reduction, and ureolysis. Ectomycorrhizal fungi dominated in the dry season, while saprotrophic fungi prevailed in the rainy season. This research advances our understanding of the microbial ecology of rhizosphere of Q. franchetii , the factors shaping its microbial communities, and the stable operation of plant and soil systems.