Rapid reduction in ecosystem productivity caused by flash droughts based on decade-long FLUXNET observations

Abstract

Abstract. A flash drought is characterized by its rapid onset and arouses widespread concerns due to its devastating impacts on the environment and society without sufficient early warnings. The increasing frequency of soil moisture flash droughts in a warming climate highlights the importance of understanding its impact on terrestrial ecosystems. Previous studies investigated the vegetation dynamics during several extreme cases of flash drought, but there is no quantitative assessment on how fast the carbon fluxes respond to flash droughts based on decade-long records with different climates and vegetation conditions. Here we identify soil moisture flash drought events by considering decline rate of soil moisture and the drought persistency, and we detect the response of ecosystem carbon and water fluxes to a soil moisture flash drought during its onset and recovery stages based on observations at 29 FLUXNET stations from croplands to forests. Corresponding to the sharp decline in soil moisture and higher vapor pressure deficit (VPD), gross primary productivity (GPP) drops below its normal conditions in the first 16 d and decreases to its minimum within 24 d for more than 50 % of the 151 identified flash drought events, and savannas show highest sensitivity to flash drought. Water use efficiency increases for forests but decreases for cropland and savanna during the recovery stage of flash droughts. These results demonstrate the rapid responses of vegetation productivity and resistance of forest ecosystems to flash drought.

Vegetation Drought Vulnerability Mapping Using a Copula Model of Vegetation Index and Meteorological Drought Index

“…Vegetation is a key component of terrestrial ecosystem and a major link between the atmosphere, water and soil [80,81]. Drought risk can have a decisive impact on the vegetation of terrestrial ecosystems [82][83][84]. Quantifying the effects of drought on vegetation plays a critical role in sustainable management of terrestrial ecosystems [85].…”

Projected U.S. drought extremes through the twenty-first century with vapor pressure deficit

“…Future drought extremes are expected to change under global warming. Current drought monitoring in the United States indicates that extreme conditions have faster onset 1 , and short-term droughts are enhanced by heat waves leading to increased drying 2 , 3 . Overall, under global warming, drought extremes are expected to increase throughout the twenty-first century 4 – 11 , ultimately affecting water resources, wildfire activities, and crop loss.…”

The Rise of Atmospheric Evaporative Demand Is Increasing Flash Droughts in Spain During the Warm Season

“…Several recent studies have suggested an escalation in droughts in future climate change scenarios linked to enhanced AED (Cook et al, 2014;Dai et al, 2018;Vicente-Serrano et al, 2020). As flash droughts are mostly relevant during the warm season, and associated with agricultural and ecological disasters (e.g., tree mortality, crop failure, increased risk of forest fires), it is reasonable to consider that future climate scenarios may be affected by more frequent and severe flash droughts, which would increase these consequences for vegetation activity and growth (Jin et al, 2019;Otkin et al, 2016Otkin et al, , 2019Zhang & Yuan, 2020). Thus, although there are some studies suggesting that drought metrics that include AED might overestimate future drought severity in comparison with metrics based on evapotranspiration (ET; Berg & Sheffield, 2018;Scheff, 2018), in fact the role of AED in the development of flash droughts is mainly restricted to water-limited areas and dry periods (e.g., Figure 2); therefore, under these conditions ET is limited by water availability.…”