Simulating Net Ecosystem Exchange of China’s Three Staple Food Crops and Their Responses to Heatwaves

Agricultural carbon sequestration is increasingly threatened by heatwaves, yet accurately simulating crop-explicit net ecosystem exchange (NEE) under heat stress remains challenging. In this study, we used a WRF–VPRM–CROP model to simulate the spatiotemporal dynamics of NEE for rice, wheat, and maize in China, quantifying the impacts of the record-breaking 2022 heatwave. Model validation against multi-source observations confirmed its reliability, with correlation coefficients (r) reaching 0.49–0.85 (p < 0.001). Results show that the cumulative summer NEE of the study region reaches 620.32 Tg C, with contributions of 274.94 Tg C from rice and 345.09 Tg C from maize, while wheat contributes 157.83 Tg C during spring. The 2022 heatwave led to substantial reductions in crop NEE, with decreases of 79.70 Tg C for rice, 33.13 Tg C for wheat, and 100.74 Tg C for maize. Total summer NEE decreased by 171.46 Tg C, with an annual reduction of 213.57 Tg C. Spatially, the most pronounced declines in NEE are concentrated in East China and North China, whereas slight increases are observed in western Heilongjiang (maize-growing areas) and parts of eastern coastal wheat-growing regions. At the provincial scale, the most severe yield losses occur in Henan (29.65 Mt) and Shandong (14.50 Mt). This study quantifies the impacts of extreme heatwaves on carbon exchange in China’s major staple crop systems, providing a scientific basis for regional agricultural climate adaptation and disaster risk mitigation.