Hierarchical ecohydrological controls on drought-driven ecosystem stability in alpine and temperate grasslands across the Qinghai–Tibetan and Mongolian plateaus

Study region: This study examines alpine and temperate grasslands across the Qinghai–Tibetan Plateau (TP) and the Mongolian Plateau (MP) during 2001–2023, representing two contrasting hydroclimatic settings in Asia. Study focus: This study aims to compare drought regimes, drought-related ecosystem response patterns, and their associated climatic pathways between alpine and temperate grasslands. Seasonal-scale drought was identified using the Standardized Precipitation Evapotranspiration Index at a 3-month timescale (SPEI-3), and ecosystem stability was quantified from monthly satellite gross primary productivity (GPP) anomalies. Four complementary stability metrics were considered, including resistance (Ω), resilience (Δ), constraint time (Ct), and recovery time (Rt). Random-forest attribution and residual-based partial correlations were combined to assess both predictor importance and directional relationships. New hydrological insights for the region under study: Temperate grasslands on the MP experienced stronger and more persistent drying, whereas alpine grasslands on the TP showed weaker and more spatially mixed drought trends. Consistent with these drought regimes, TP grasslands generally showed higher resistance and shorter Ct/Rt, while MP grasslands exhibited lower resistance but higher resilience and longer drought impacts. RF and partial-correlation analyses revealed a hierarchical contrast in climatic associations: TP stability was primarily linked to atmospheric demand and moisture–productivity coupling including vapor pressure deficit, soil water conditions, radiation and GPP, whereas MP stability was more strongly associated with energy-related conditions especially temperature and radiation, with atmospheric demand additionally shaping resilience. These findings indicate that drought-driven stability differs not only in magnitude but also in directional climatic associations, highlighting distinct drought buffering and post-drought recovery pathways across the two plateau systems.