Abstract: Aims Environmental gradients and human disturbance are key drivers affecting soil microbial communities and biodiversity, yet their combined effects on soil legacy processes and subsequent plant growth remain poorly understood. Methods We conducted a study in the Shennongjia region of Hubei Province, China. Plots characterized by three disturbance levels—Low, Medium, and High disturbance—were established along an elevational gradient ranging from 500 to 3000 m. By combining field sampling with a greenhouse common garden experiment, we systematically evaluated the impacts of elevational gradients and human disturbance on soil microbial communities and the resulting soil legacy effects on plant growth. Important findings Elevation significantly reduced the α-diversity of soil bacteria and fungi and markedly altered microbial community composition, whereas the direct effects of human disturbance on microbial community structure were relatively weak. Soil legacy effects varied significantly across human disturbance levels, with medium disturbance markedly amplifying the positive effects of soil legacies on plant total biomass, while these effects weakened or became neutral under low and high disturbance conditions. The legacy effects on the root-to-shoot ratio showed a significant interaction between elevation and disturbance, indicating that the response of plant resource allocation strategies to soil historical conditions is strongly environmentally dependent. Structural Equation Modeling (SEM) further revealed that elevation indirectly influenced plant traits primarily through its effects on fungal communities, while interactions between fungal and bacterial communities regulated the direction and magnitude of soil legacy effects. Overall, soil legacy effects serve as a key mechanism linking elevational gradients, human disturbance, and plant growth responses, with their ecological importance being particularly pronounced under medium disturbance conditions. This study highlights the necessity of incorporating soil legacy effects when predicting subtropical mountain vegetation dynamics in the context of global change.

Key words: Shennongjia, elevation, disturbance, soil legacy effect, annual Asteraceae species