Increasing susceptibility and shortening response time of vegetation productivity to drought from 2001 to 2021

Drought generally causes the significant reduction of vegetation productivity. Most studies focus on the vegetation response to gradual water variabilities instead of anomalies in water availability, however, the spatiotemporal patterns of vegetation response to extreme water deficits during drought are still unclear. Here, based on leaf area index (LAI) and solar-induced chlorophyll fluorescence (SIF), we employed coincidence analysis to identify the susceptibility and response time of vegetation productivity to drought, and further investigated the spatiotemporal changes of them during 2001-2021 across the globe. We found stronger susceptibility and shorter response time both in areas occupied by more grasses and in more arid regions. Temporally, we revealed a predominately increasing susceptibility (P < 0.05) and shortening response time (P < 0.05) in drought-sensitive regions from 2001 to 2021. These changes have been majorly attributable to the elevated atmospheric CO2, which tended to strengthen the susceptibility in areas covered by more grasses and in arid regions. Our finding highlighted the increasing risk of decline in vegetation production under drought particular in grasslands and drylands.