Divergent impacts of flash drought drivers on alpine ecosystem resilience

Flash droughts are escalating globally, yet the divergent impacts of their thermodynamic and hydraulic drivers on alpine ecosystem resilience remain unresolved. Focusing on the Yarlung Tsangpo River Basin (2000-2023), we integrated a multivariate drought identification framework with a Kalman filter-based Bayesian linear dynamic model to quantify ecosystem resilience dynamics in response to flash drought. While widespread resilience degradation was observed across 92% of the basin, our analysis reveals a novel and counter-intuitive divergence. Specifically, soil moisture deficits-driven flash drought consistently weakened ecosystem resilience, whereas temperature-driven events triggered a transient resilience enhancement. The latter showed a positive correlation between resilience enhancement and temperature anomaly contribution (R² = 0.64). This temporary boost to meltwater subsidies from thawing permafrost and physiological thermal acclimation for alpine ecosystems, which effectively may mask underlying tipping points. However, this impact is highly heterogeneous: grasslands and shrublands in the mid-upper reaches suffered severe resilience loss, whereas forests demonstrated remarkable buffering capacity. Furthermore, increasing flash drought frequency, intensity, and duration were all strongly associated with declining resilience, with high-frequency events being particularly detrimental. These findings challenge the common view on drought impacts, revealing a masked resilience response in alpine ecosystems, highlighting that their stability may be temporary. This underscores the critical importance of protecting high-altitude forests as a core climate adaptation strategy.