Effects of extreme temperature events on carbon fluxes in different ecosystems in the Heihe River Basin, China

The terrestrial carbon cycle is strongly influenced by climate changes, but the impact of extreme temperature events on carbon fluxes in Northwest China's ecosystems remains poorly understood. To understand the impacts of extreme temperature events on carbon fluxes, we measured net ecosystem productivity (NEP), gross primary productivity (GPP), and ecosystem respiration (Reco) along with meteorological factors at nine sites in the Heihe River Basin (HRB) from 2013 to 2022. Extreme high temperature (EHT) and extreme low temperature (ELT) were identified based on long-term air temperature data and their impacts on carbon fluxes were examined. Our findings indicate a rising frequency of EHT events and a decline in ELT events during the growing seasons over the past decade. During the EHT periods, GPP and Reco generally increased, regardless of soil water content. In contrast, both GPP and Reco decreased during the ELT periods. Alpine grasslands are more sensitive to EHT events, while deserts exhibit more sensitivity to ELT events. These results highlight the diverse responses of carbon fluxes to extreme temperature events across ecosystems in the HRB, providing valuable insights for regional ecosystem management and climate change adaptation.