Divergent responses of rhizosphere microbial diversity and co-occurrence patterns to elevation and season in Quercus franchetii from the Yuanmou dry‑hot valley, Southwest China

BACKGROUND: Dry-hot valleys suffer from severe ecological stress, with the rhizosphere being an essential microhabitat for plant adaptation. Elevation and seasonal changes are key drivers shaping rhizosphere microbial diversity and community composition. However, their impacts on rhizosphere bacteria and fungi associated with Quercus franchetii in dry-hot valleys remain poorly understood. RESULT: Bacterial α-diversity exhibited a V-shaped pattern along the elevational gradient, whereas fungal α-diversity generally declined with increasing elevation. Seasonal effects were pronounced, with both bacterial and fungal diversity higher in the rainy season. Soil pH had strong positive correlations with bacterial α-diversity, and both soil pH and water content were associated with variations in bacterial and fungal community composition. Bacterial co-occurrence networks were more complex than fungal networks. Rainy-season networks had higher natural connectivity, and higher random and targeted robustness AUC. Actinobacteriota, Acidobacteriota, and Ascomycota acted as keystone taxa stabilizing network interactions. Functional predictions indicated that bacterial communities were predominantly chemoheterotrophic, whereas fungal communities were dominated by symbiotrophic guilds. CONCLUSIONS: Elevational gradients exert a stronger influence than seasonal variation on rhizosphere microbial diversity and composition. Soil pH and water content are key environmental filters shaping microbial assemblages. Microbial networks maintain ecosystem functions through seasonally modulated connectivity and cooperation. Keystone taxa may mediate network stability and functional resilience under spatiotemporal environmental variation. These results provide a basis for predicting microbial responses to environmental change in dry-hot valleys.