Assessment of CH4 flux and its influencing drivers in the rice-wheat agroecosystem of the Huai River Basin, China

To understand the CH4 flux variations and their climatic drivers in the rice-wheat agroecosystem in the Huai River Basin of China, the CH4 flux was observed by using open-path eddy covariance at a typical rice-wheat rotation system in Anhui Province from November 2019 to October 2021. The variations and their drivers were then analyzed with the Akaike information criterion method. CH4 flux showed distinct diurnal variations with single peaks during 9:00~13:00 local time. The highest peak was 2.15 µg m-2 s-1 which occurred at 11:00 in the vegetative growth stage in the rice growing season (RGS). CH4 flux also showed significant seasonal variations. The average CH4 flux in the vegetative growth stage in the RGS (193.8±74.2 mg m-2 d-1) was the highest among all growth stages. The annual total CH4 flux in the non-rice growing season (3.2 g m-2, 11.8%) was relatively small compared to that in the RGS (23.9 g m-2, 88.2%). CH4 flux increased significantly with increase in air temperature, soil temperature, and soil water content in both the RGS and the non-RGS, while it decreased significantly with increase in vapor pressure deficit in the RGS. This study provided a comprehensive understanding of the CH4 flux and its drivers in the rice-wheat rotation agroecosystem in the Huai River Basin of China. In addition, our findings will be helpful for the validation and adjustment of the CH4 models in this region.