Title：
Landscape-scale vegetation cover shapes microbial community assembly and functional potential via Erosion-driven nutrient patterns in Alpine Rivers
Soil erosion on the Qinghai-Tibetan Plateau has been a critical ecological issue, strongly impacted by vegetation cover on mountain slopes. However, the impact of soil erosion on microbial communities in alpine rivers remains largely unexplored, particularly regarding the planktonic and benthic microbiomes of alpine river ecosystems. This study analysed the community structure and functional potential of planktonic microbiomes in water and benthic microbiomes in alpine riparian sediments on the Qinghai-Tibetan Plateau, under two distinct normalised difference vegetation index (NDVI) fluctuation conditions, using high-throughput sequencing and carbon, nitrogen, phosphorus, and sulphur gene chips. The results revealed the role of microorganisms in regulating elemental cycling in eroded alpine rivers. The lower NDVI basin correlated with elevated nutrient concentrations in riparian sediments and higher benthic microbial diversity, whereas planktonic habitats exhibited the opposite pattern. The community assembly of microbial communities in the low-NDVI basin (Lhasa River) was more strongly constrained by dispersal limitation, leading to greater stochasticity in both planktonic and benthic communities. Network dynamics from summer (T6) to autumn (T9) indicated that inter-basin NDVI variations primarily modulate protist-driven associations. Notably, the low-NDVI Lhasa River basin (T9) exhibited a 1.8fold increase (Lhasa River at T9 vs. Nyang River at T3) in carbon-degradation genes (xylA, abfA, frdA, rbcL), suggesting microbial functional shifts that may amplify carbon export. Overall, NDVI regulates carbon/nitrogen cycling through nutrient-driven bacterial processes and functional gene coupling, as revealed by partial least squares path modelling. These findings elucidate the structural and functional dynamics of eroded alpine river microbial communities while providing empirical evidence for top-down regulation across NDVI gradients.
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