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

Abstract

Flash droughts, as sub-seasonal phenomenon, are characterized by their rapid onset and significant impact on terrestrial ecosystems. However, understanding how vegetation responds to flash droughts and mechanisms governing vegetation recovery remains elusive. Here, we analyzed the response of vegetation productivity to flash droughts and the most relevant drivers in post-flash drought vegetation recovery during the growing season using two soil moisture datasets (ERA5-land and GLDAS) and two satellite-based vegetation productivity proxies (Gross Primary Productivity, GPP and Solar-induced chlorophyll fluorescence, SIF). Our results show that South China and Northeastern 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, its speed is very high, with a median of 10.9% per pentad. Most ecosystems can recover to their normal state within 25 days. 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 provided valuable insights into the mechanisms underlying vegetation responses to flash droughts.