The Hydrothermal Regulation of Methane Flux in China’s Largest Semi-Fixed Desert

Based on eddy covariance data collected during March to June 2021 in the Gurbantunggut Desert, this study analyzed desert methane (CH4) flux dynamics. Results show the following: (1) The desert functions as a weak methane sink from March to June in the growing season, with its CH4 flux showing a U-shaped diurnal variation pattern. The absorption peak occurred in June, reaching −79.1 mg·m−2·month−1. (2) Diurnally, CH4 flux correlated negatively with soil temperature (Tsoil), vapor pressure deficit, and photosynthetically active radiation (rTsoil = −0.58, rVPD = −0.49, rPAR = −0.49), positively with soil water content (SWC) and relative humidity (RH) (rRH = 0.53, rSWC = 0.28). (3) Fixed-effects regression isolated individual and interactive effects of SWC and Tsoil, yielding the model: CH4 = −0.002 − 0.017SWC − 0.00004Tsoil − 0.002(SWC × Tsoil). The model highlights CH4 flux sensitivity to hydrothermal factors and underscores the importance of their interaction for accurate flux estimation and understanding arid zone carbon cycle-climate feedbacks.