Dominant Biophysical Cooling of Winter Wheat Cultivation in China: An Integrated Biogeochemical and Biophysical Assessment

Agricultural ecosystems influence climate through both biogeochemical (BGC) processes by exchanging greenhouse gases and biophysical (BGP) processes by modifying surface energy balance. While BGC processes have been the focus of climate assessments, the role of BGP processes in regulating local temperature remains poorly understood. In this study, we quantify the climate effects of winter wheat cultivation across China from 2001 to 2020, considering both the BGC and BGP processes. Our integrated assessment reveals that winter wheat cultivation induced a net cooling of −1.05°C in land surface temperature (LST). This outcome was dominated by a pronounced BGP effect, which contributed −0.96°C (91% of the total) via strong nighttime cooling (−2.21 ± 0.64°C) partially counteracted by slight daytime warming (0.01 ± 1.43°C). Notably, the net cooling effect has significantly attenuated over the past two decades, showing a trend of 0.02°C annually. In terms of BGC processes, winter wheat functioned as a strong carbon sink, with a mean net biome productivity (ΔNBP) of 302.55 t CO 2 /km 2 , equivalent to a cooling of −0.07°C (6% of the total effect). This was partially offset by N 2 O emissions (averaging 89.98 t CO 2 eq/km 2 ), inducing a warming of +0.02°C. Overall, the BGP process dominates the climate impacts of winter wheat, underscoring the importance of considering both BGP and BGC processes in evaluating cropland climate regulation.