Diversity patterns and drivers of soil bacterial and fungal communities in alpine meadows on the eastern Qinghai-Tibet Plateau

Soil microbial communities are fundamental to ecosystem functioning, and their roles are particularly critical in high-altitude environments characterized by harsh climatic conditions and nutrient limitations. However, the responses of bacterial and fungal communities, particularly the intra- and inter-kingdom interactions among bacterial and fungal taxa, to latitudinal gradients in alpine ecosystems remain poorly understood. In this study, we found that bacterial diversity significantly increased with latitude (R² = 0.60, p < 0.001), with the soil C:N ratio and total phosphorus identified as the key predictors. In contrast, overall fungal diversity exhibited no significant latitudinal trend, although saprotrophic fungi showed a weaker positive response primarily driven by dissolved nitrogen availability. Bacterial community composition was mainly influenced by soil pH, mean annual temperature (MAT), and electrical conductivity, whereas fungal communities were primarily shaped by MAT and precipitation, reflecting their distinct environmental sensitivities. Network analysis revealed that bacterial interactions became increasingly complex with latitude, likely as an adaptation to environmental stress, whereas fungal networks remained relatively stable, possibly due to their higher stress tolerance and reliance on symbiotic associations. Furthermore, bacterial–fungal associations strengthened with latitude, suggesting increased microbial cooperation under harsher conditions. Overall, these findings reveal fundamental differences in the ecological strategies of bacteria and fungi and emphasize the role of environmental gradients in shaping microbial community structure and interactions. This study contributes to a deeper understanding of microbial biogeography in alpine ecosystems and provides insights into how microbial communities may respond to environmental changes in high-altitude regions.