Central Asian vegetation is more sensitive to soil moisture drought than to heat and meteorological drought

While Central Asian ecosystems are increasingly threatened by heat and drought, the precise nonlinear trajectories and temporal sensitivities of vegetation to these diverse stressors remain poorly understood. This study used datasets from Central Asia (1982-2019) for Gross Primary Productivity (GPP), Fractional Vegetation Cover (FVC), and Leaf Area Index (LAI) to represent vegetation productivity, cover, and leaf area, respectively. We further employed the Standardized Temperature Index (STI), Standardized Precipitation Index (SPI), and Standardized Soil Moisture Index (SSMI) to characterize heat, meteorological drought, and soil moisture drought, respectively. Using the Breaks For Additive Season and Trend (BFAST) algorithm, rank-correlation analysis, and a sensitivity-analysis framework, we investigated-across spatial gradients, vegetation types, and climate zones-the nonlinear trends of these vegetation characteristics and the timing and sensitivity of their responses to heat and drought. The results showed that the nonlinear spatial trends in vegetation GPP, FVC, and LAI were dominated by "interrupted increase" (defined as a trend with one significant abrupt change, showing an overall increasing pattern interrupted by a single notable negative disturbance), with increases exceeding decreases. On a regional average, soil moisture drought had the longest mean duration (17.28 months), meteorological drought exhibited the greatest mean intensity (19.60, unitless standardized index sum), and heat events occurred most frequently (13.53 events per pixel). Heat and drought exerted both cumulative and lagged effects on multiple vegetation characteristics. Specifically, the cumulative influence of meteorological drought persisted for 7-8 months; the lag effect of soil moisture drought was shorter, lasting only 1-3 months; and for heat, the cumulative and lag windows were concentrated at 4-6 months and 2-5 months, respectively. Sensitivity of vegetation-classified via Jenks natural breaks based on correlation strength and response times-was high for heat, low to moderate for meteorological drought, and extreme for soil moisture drought. This study provides essential theoretical insights and an empirical evidence base to inform regional ecosystem management and the formulation of sustainable development policies. This work provides essential theoretical insights and empirical evidence to guide sustainable policy design.