Effects of a Road Corridor on Plant Diversity and Species Turnover on the Qinghai–Tibet Plateau

Road infrastructure can alter plant diversity and community composition, yet its effects on multisite species turnover in high-elevation ecosystems remain poorly understood. We investigated herbaceous and shrub communities along the Sino–Nepalese our investigation was carried out along the Transport Corridor on the Qinghai–Tibet Plateau using 420 vegetation plots across 28 sites. Mixed-effects models, zeta diversity, and multi-site generalised dissimilarity modelling (MS-GDM) were used to assess the effects of the road corridor on local diversity, species turnover, and their drivers. Distance from the road was significantly associated with species richness in both vegetation types but had no significant effect on Shannon diversity. Shrub communities exhibited stronger compositional turnover and lower multisite species sharing than herbaceous communities. Elevation and geographic distance showed the strongest contributions to turnover across most species groups. Soil pH additionally contributed strongly to shrub turnover weighted towards locally restricted species, whereas annual average daily traffic (AADT) contributed to turnover weighted towards locally restricted and more widespread herbaceous species. AADT did not significantly affect herbaceous richness or Shannon diversity, suggesting that traffic intensity was more clearly associated with species composition than with local diversity. These findings highlight contrasting responses of shrub and herbaceous communities and demonstrate the importance of considering species turnover when assessing the ecological effects of high-elevation transport corridors.