Seasonal Differences in Vegetation Susceptibility to Soil Drought During 2001–2021

Droughts typically exert negative effects on vegetation growth, which largely depend on the timing of drought onset. However, huge inconsistencies exist in the seasonal vegetation response to drought among diverse regions across the globe. Here, using the leaf area index (LAI) and solar-induced chlorophyll fluorescence (SIF), we quantified the vegetation susceptibility by calculating the coincidence rate between vegetation suppression extremes and soil droughts, and further investigated the spatiotemporal changes of vegetation susceptibility during different seasons from 2001 to 2021. We found the vegetation during summer and dry seasons were most susceptible to soil droughts in the extra-tropics and tropics, respectively. Temporally, the autumn vegetation susceptibility was strengthening in drought-susceptible regions of extra-tropics, albeit with insignificant change during spring, summer and the entire growing season. Both the dry and wet seasons showed evidently increasing vegetation susceptibility on the dry tropical ecosystems, which dominated the enhanced vegetation susceptibility of global drought-susceptible regions. Our findings determined the spatial pattern of most susceptible seasons to soil droughts across the globe and highlighted the enhanced risk to soil droughts, especially in the dry tropics.