Evaluation of ecosystem’s response to flash drought in water-limited regions of China

Intensive and frequent flash droughts pose a threat to the stability of terrestrial ecosystems and affect land carbon sinks, particularly in vulnerable water-limited regions. Here, we evaluated variations in flash drought events in water-limited regions of China from 2001 to 2022 and quantified vegetation resistance (its ability to maintain predrought level) and resilience (its capacity to bounce back from droughts) to flash drought based on solar-induced chlorophyll fluorescence and gross primary productivity. The average frequency of flash droughts was approximately 3.5 events per decade and the duration increased significantly by 3 d during 2001-2022. We found that vegetation resistance to flash drought did not show significant temporal changes, while resilience decreased significantly. Spatially, as aridity increased, vegetation resistance gradually decreased while resilience rose. The strong negative correlation between resistance and resilience demonstrated a trade-off in individual climate regions, which varied among different vegetation types. Among eight vegetation types, evergreen needleleaf forest, evergreen broadleaf forest and mixed forest displayed high-resistance and low-resilience, while deciduous needleleaf forest exhibited both high-resistance and high-resilience. Furthermore, we revealed that aridity index, vapor pressure deficit, and temperature were the most relevant environmental variables for both vegetation resistance and resilience, but had opposite effects and different magnitudes. Our findings highlight that the vulnerability and stability of terrestrial ecosystems are decreasing and are affected by water availability.