Evaluation of the resistance and resilience of terrestrial ecosystems to drought in southwest China

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The increasing frequency and intensity of climate extremes have profound impacts on ecosystem function, structure, and stability. Drought is one of the most complex hydrological and climate disasters, and its intensity and duration cause varying degrees of damage to terrestrial ecosystems. Resistance and resilience are crucial concepts for recognizing and understanding the effects of ecosystems on drought events. However, little research has been carried out in southwest China, which experienced severe drought between 2000 and 2018. In this study, the 3-month standardized anomaly (SA) of the Stand Precipitation-Evapotranspiration Index (SPEI) was used to assess ecosystem drought parameters, including onset, duration, severity, and recovery time in 8 plant functional types (PFTs) across the ecosystems in southwest China. By combining vegetation greenness and productivity data, including vegetation greenness indices of Enhanced Vegetation Index (EVI), Normalized Difference Vegetation Index (NDVI), Leaf Area Index (LAI), and productivity index of Gross Primary Production (GPP), the resistance and resilience of the ecosystem were quantified. Our results showed that, spatially, northwestern and southeastern Sichuan and southeastern Yunnan experienced severe drought. Compared to vegetation productivity of GPP (SA value is 0.03), the vegetation greenness indices of EVI (SA value is 0.07), NDVI (SA value is 0.07), and LAI (SA value is 0.20) exhibited lower vulnerability to droughts. Furthermore, the effects of drought on ecosystem resistance and resilience varied with vegetation indices and PFTs, and resistance (mean value is 0.72) was greater than resilience (mean value is 0.56). Across different PFTs, there was a trade-off between resistance and resilience: higher resistance tended to have lower resilience in forests and woody savannas. These findings propose ways to enrich our understanding of ecosystem resistance and resilience to droughts, and recommend the importance of using validated sensitivity indicators to quantify the ecosystem’s resistance and resilience to droughts.