Soil moisture constraints override atmospheric aridity in governing vegetation dynamics on the warming Qinghai-Tibetan plateau

Vegetation dynamics across the warming Qinghai-Tibet Plateau (QTP) exhibit marked sensitivity to both atmospheric and soil moisture stress. Yet, quantifying their relative roles in limiting vegetation growth remains contentious and is hindered by their tight coupling through land-atmosphere interactions. To disentangle the effects of atmospheric and soil moisture stress on vegetation dynamics, this study leverages binning sensitivity analysis and long-term datasets (including AVHRR Normalized Difference Vegetation Index (NDVI), Vapor Pressure Deficit (VPD), GLEAM Soil Moisture (SM), and Evapotranspiration (ET)) to quantify their respective roles. Our findings indicate that: (1) breakpoint trend analysis indicated that 58.65% of QTP vegetation underwent regime shifts, transitioning from sustained greening (0.009/10a, pre-2000) to accelerated degradation (−0.0036/10a, post-2000). The most pronounced reversals occurred in the central-western endorheic basins under warming-drying climatic trends and in exorheic basins shifting from warm-wet to warm-dry conditions. (2) Nonlinear SM-VPD interactions explain over 60% of degradation hotspots, with divergent regional trends: northwestern/southern regions showed SM trend reversals (24.9% decreasing after 2000 vs 39.4% increasing in northeast), while VPD exhibited a dipole pattern (40.3% in central-west/south shifting to increasing vs 25.9% in northeast decreasing post-2000). (3) Decoupling analysis identified SM as the primary driver of vegetation dynamics (critical threshold: 0.229 m 3 m −3 ). Exorheic basins were increasingly controlled by atmospheric aridity, whereas endorheic basins showed amplified SM limitations—particularly in southwestern coniferous forests and mid-elevation (3000–4000 m) alpine grasslands. These results advance our understanding of land-atmosphere coupling effects on vegetation changes. • Vegetation underwent regime shifted from sustained greening to accelerated degradation before and after 2000 on the Warming Qinghai-Tibetan Plateau. • Nonlinear SM-VPD interactions explained over 60% of degradation hotspots. • Soil moisture identified as the primary driver of vegetation dynamics (critical threshold: 0.229 m 3 m −3 ). • Alpine grasslands at 3000–4000 m exhibiting acute SM stress responses.