Loss and recovery of vegetation productivity in response to extreme drought during 2022 across China

Extreme droughts can severely impact terrestrial vegetation productivity. In the summer of 2022, approximately 32.7% of China's land area experienced extreme drought conditions, marked by reduced rainfall both in terms of amount and intensity, prolonged consecutive dry days, minimal rainy days, and accompanied by heat waves. While previous studies have reported productivity losses in over half of China's vegetated areas in 2022, how vegetation productivity recover from extreme drought remains to be clarified. In this study, we utilized the Enhanced Vegetation Index (EVI), Gross Primary Productivity (GPP) and meteorological data to evaluate the extent and pace of vegetation productivity change from loss in 2022 to post-drought recovery in 2023. We also assessed the contributions of seven meteorological variables and two drought-related variables to variations in vegetation productivity in regions affected by extreme drought using machine-learning techniques. Our findings revealed that, in 2022, the average EVI and GPP in regions affected by extreme drought were 2.3% and 8.0% lower, respectively, compared to the baseline period from 2018 to 2021. Soil water content (SWC) emerged as the primary factor contributing to the decline in EVI/GPP, followed by the number of rainy days for EVI and vapor pressure deficit for GPP. In 2023, we observed a significant vegetation recovery, with the average EVI increasing by 2.6% and the GPP rising by 14.9% within the study area compared to 2022. SWC played a dominant role in this recovery, and both EVI recovery and GPP recovery displayed a non-linear response to SWC. Additionally, we identified a threshold effect for SWC on recovery; once SWC increased above a certain threshold, EVI and GPP would recover largely and rapidly. Furthermore, rainfall intensity and rainfall amount emerged as the second most important factors influencing the recovery of EVI and GPP, respectively. Our study underscores the significance of soil moisture and rainfall seasonality in influencing plant growth.