Aims <p>Alpine environments impose strong constraints on plant reproduction by altering resource availability, soil conditions, and plant-soil interactions, frequently shifting the balance between sexual and asexual reproduction. Root-associated fungal communities, as a key biological interface between plants and soil, may mediate these environmental effects through their influence on plant carbon and nutrient allocation. Nevertheless, whether and how such fungal communities are associated with plant reproductive strategies across environmental gradients remains poorly understood.</p> Methods <p>In this study, we sampled <i>Bistorta vivipara</i>, a species widely distributed in alpine and arctic ecosystems, across six altitudes on the northeastern Qinghai-Tibet Plateau. At each altitude, plant traits were measured and soil samples were collected for physicochemical analyses, whereas root samples were used for DNA extraction and high-throughput sequencing to characterize root-associated fungal communities.</p> Results <p>Total reproductive allocation increased with altitude, whereas the proportion of flowers per inflorescence declined, indicating a shift toward greater asexual allocation. Root-associated fungal communities showed significant compositional turnover along the altitudinal gradient, and their composition was more strongly associated with reproductive traits than with vegetative and nutritional traits, soil properties, or fungal richness. The relative abundances of most ectomycorrhizal fungal OTUs were negatively correlated with both reproductive allocation and the proportion of flowers per inflorescence.</p> Conclusions <p>Our results suggest that plant reproductive strategies shift along altitudinal gradients and are closely linked to root-associated fungal communities. These findings highlight the potential importance of plant–microbe associations in reproductive allocation and provide new insights into the belowground dimensions of plant adaptation to alpine environments.</p>