Spatial differentiation of ecosystem resilience and asymmetric response mechanisms under flash drought stress in Asian Karst Concentration areas

Study region The Asian Karst Concentration, spanning southwestern China and the Indochina Peninsula. Study focus This study aimed to determine how karst geomorphology regulates ecosystem resistance and recovery under flash drought stress. We integrated satellite-derived gross primary productivity, evapotranspiration, soil moisture, and evaporative stress index datasets from 2000 to 2024, and applied a multidimensional resilience framework, nonlinear threshold detection, and soil moisture–water use efficiency coupling analysis. New hydrological insights for the region The estimated karst–non-karst contrast in GPP-based resistance was sensitive to spatial grouping and uncertainty assumptions, while karst areas exhibited a smaller next-year productivity rebound. Estimated breakpoints in the resistance–severity relationships differed between karst and non-karst areas (52.8 vs. 105.2), with distinct changes in fitted slopes rather than a common physiological collapse pattern. Median soil moisture–water-use efficiency correlations were higher in karst areas within each aridity class, although the direction of the contrast varied among aridity–vegetation combinations. Event composites showed less negative standardized soil-moisture minima but more negative water-use-efficiency minima in karst areas. Together, these findings highlight the importance of considering productivity maintenance, subsequent rebound, and water-related responses jointly when assessing flash-drought vulnerability. Hydrological heterogeneity provides a plausible explanation for these contrasting responses, but the contribution of subsurface buffering requires independent validation.