Analysis of drought response thresholds and drought-causing factors of central Asian vegetation

• This research evaluates the responses of Central Asian vegetation to drought. • A new framework is proposed to calculate drought causative factors for vegetation. • Drought response thresholds were significantly different for different vegetation. • Quantitative assessment of drought thresholds is essential for drought risk mitigation. Understanding the threshold responses of vegetation to drought is essential for predicting and mitigating drought risk. Across Central Asia, extreme weather is expected to increase by the end of the 21st century. However, the threshold responses of different Central Asian vegetation types are not well understood. Here, we calculated drought indices for Central Asia based on meteorological data and remotely sensed vegetation indices from 2001 to 2020, used trend analysis to assess changes in drought and vegetation in Central Asia over the past 20 years, evaluated the threshold responses of five vegetation types to drought, and explored the drought causative factors of different vegetation types using coexistence analysis. All five Central Asian vegetation types responded to increasing drought in a nonlinear manner, and thus exhibited drought-responsive thresholds. Forests were the first responders to increasing drought, and wetlands were the least responsive overall. Grasslands, cultivated lands, shrublands, and forests crossed the drought threshold in different years between 2001 and 2020, with shrublands exhibiting the largest percentage of area crossing the threshold. Finally, the drought causative factor for grasslands, shrublands, and wetlands was soil moisture; for cultivated lands was precipitation; and for forests was saturated water vapor pressure difference. This study uncovers the characteristic responses of different Central Asian vegetation types to drought, and lays a theoretical foundation for drought assessment and ecological restoration in Central Asia.

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