Increasing susceptibility of vegetation productivity to compound drought from 2001 to 2020

The atmospheric and soil droughts have exerted substantial effects on vegetation productivity, and generally occur simultaneously due to land-atmospheric feedback. However, the temporal changes in vegetation response to soil droughts, atmospheric droughts, and their compound droughts remain largely unknown. Using vapor pressure deficit (VPD), soil moisture (SM), and two vegetation indexes including the leaf area index (LAI) and solar-induced chlorophyll fluorescence (SIF), here we quantified the vegetation susceptibility to these three drought types via coincidence analysis and evaluated the spatiotemporal patterns of them. Spatially, we found most of global vegetated areas (63.8 %) were more susceptible to compound droughts, with the higher vegetation susceptibility to them in the areas with less tree cover and more arid climate, respectively. Temporally, we revealed a predominated increasing trend (0.0027 year −1 for LAI and 0.0023 year −1 for SIF, P < 0.05) in vegetation susceptibility to compound droughts over drought-susceptible regions during 2001–2020. Our finding highlighted an increasing ecosystem vulnerability to compound droughts, which could pose more threats on the stability of land carbon sink under future climate. • 63.8 % of global vegetated areas were more susceptible to compound droughts in compared with atmoshperic and soil droughts. • The areas with less tree cover and more arid climate were highly susceptible to compound droughts. • The global drought-susceptible regions showed a increasing susceptibility to compound droughts during 2001-2020.