Spatiotemporal characteristics of Net Ecosystem Exchange in the Beijing-Tianjin sand source region and its response to drought

•For the past 40 years, theBeijing-Tianjin sand source region has been a carbon sink.•As drought intensifies, the negative impact of drought on Net Ecosystem Exchange becomes more pronounced.•In this region, grassland Net Ecosystem Exchange is most affected by and sensitive to drought.•Moisture limitation is the main driver of carbon source/sink change in this region. In the context of global change, the carbon budget in arid and semi-arid regions have changed significantly. Understanding these dynamic features and their response to climate change is essential for regional carbon cycle assessments. The Beijing-Tianjin Sand Source Region (BTSSR), a significant ecological project in China, is central to studies on carbon budget dynamics. While global change intensifies, understanding its carbon budget response to drought is crucial. By integrating data from the Net Ecosystem Exchange (NEE) and the Standardized Precipitation Evapotranspiration Index (SPEI), we analyzed the spatiotemporal attributes of NEE in this region and its response to drought. The BTSSR is currently in a carbon sink state, with the mean NEE being −45.13 gCm−2 and a rate of change at −0.005 gCm−2a-1. The maximum carbon sink occurs during the summer, whereas the winter is characterized by a net release of carbon to the atmosphere. In terms of spatial variation, the NEE shifts from positive to negative from southeast to northwest across the region. The impact of drought on summer NEE is notably significant, with the correlation and sensitivity being −0.717 (p