Heterogeneity in vegetation recovery rates post-flash droughts across different ecosystems

Flash droughts, as sub-seasonal phenomena, are characterized by their rapid onset and significant impact on terrestrial ecosystems. However, understanding how vegetation responds to flash droughts and the mechanisms governing vegetation recovery remains elusive. Here, we analysed the response of vegetation productivity to flash droughts and identified the most relevant drivers controlling vegetation recovery using two soil moisture datasets (ERA5-land and Global Land Data Assimilation System) and two satellite-based vegetation productivity proxies (gross primary productivity, and solar-induced chlorophyll fluorescence). Our results show that South China and Northeast China stand out as hotspots for flash droughts, with higher frequency and speed. Notably, although the frequency of flash droughts in cropland is relatively low, and their speed is very high, with a median of 10.9% per pentad. Most ecosystems can recover to their normal state within 25 d. Vegetation with shallow roots, such as cropland and grassland, responds rapidly to flash droughts. Ecosystems generally exhibit extended response time with increasing plant rooting depth. The recovery rate of vegetation productivity from flash droughts is mainly controlled by vegetation physiology (decline rate of productivity upon exposure to flash drought) and modulated by flash drought characteristics, especially severity for forests and speed for cropland and grassland. This study provides valuable insights into the mechanisms underlying vegetation responses to flash droughts.