Gross primary productivity is more sensitive to accelerated flash droughts

Abstract

Flash droughts, characterized by their rapid onset, substantially affect terrestrial ecosystems. However, the sensitivity of ecosystem productivity to the rapid development of flash droughts under varying vegetation conditions remains poorly understood. Here we investigate the ecosystem response to the speed of flash drought onset for different plant functional types, considering the decline rate of root-zone soil moisture and standardized gross primary productivity anomaly. Our findings reveal a significant increase of approximately 10% in the proportion of 1- and 2-pentad (5 and 10 days) onset flash droughts leading to negative standardized gross primary productivity anomalies during 2001–2018. Furthermore, while standardized gross primary productivity anomalies decline at higher rates, they do not promptly respond on a shorter timescale to faster-onset flash droughts compared to slower-onset flash droughts. Vegetation types with shallower root systems exhibit higher sensitivities to faster-onset flash droughts, suggesting an escalating threat to terrestrial ecosystems in a changing climate.