Widespread consistent but rapid response of terrestrial ecosystem photosynthesis and respiratory to drought

Abstract

Drought significantly threatens terrestrial ecosystems health, through influencing both photosynthesis and respiratory processes. However, whether these processes have changed in response to intensified drought and the driving mechanisms remain unclear, even though the inconsistent responses may indicate an increased potential for unstable carbon sinks. The knowledge gap would hinder accurate prediction of the size of China's future terrestrial ecosystems carbon sink under increasing extreme droughts, thus impacting the realization of China's carbon neutrality goal. Here, we combined observational-based data and dynamic global vegetation model data to explore the response time (RT) of Gross Primary Productivity (GPP) and Ecosystem Respiration (TER) to meteorological drought in China and their dynamics over the past 40 years. Results reveal consistent spatial distribution patterns in GPP and TER responses to drought. During 1982–2021, widespread declines in the RT of both GPP and TER to drought were observed, indicating an increased likelihood of vegetation converting from a carbon sink into a carbon source under droughts. GPP responds slightly faster than TER, notably in arid regions influenced by land cover change and climate change. Hotspots of decreasing RT trends, such as the Tibetan Plateau and Yellow River Basin, underscore the diverse impacts of climate and land cover changes. Our findings shed new insights into ecosystem carbon fluxes mechanisms, thus providing accurate carbon budget for China's carbon neutrality goal.