More enhanced non-growing season methane exchanges under warming on the Qinghai-Tibetan Plateau

Uncertainty in methane (CH₄) exchanges across wetlands and grasslands in the Qinghai-Tibetan Plateau (QTP) is projected to increase due to continuous permafrost degradation and asymmetrical seasonal warming. Temperature plays a vital role in regulating CH₄ exchange, yet the seasonal patterns of temperature dependencies for CH₄ fluxes over the wetlands and grasslands on the QTP remain poorly understood. Here, we demonstrated a stronger warming response of CH₄ exchanges during the non-growing season compared to the growing season on the QTP. Analyzing 9745 daily observations and employing four methods -regression fitting of temperature-CH₄ flux, temperature dependence calculations, field-based and model-based control experiments-we found that warming intensified CH₄ emissions in wetlands and uptakes in grasslands. Specifically, the average reaction intensity in the non-growing season surpasses that in the growing season by 1.89 and 4.80 times, respectively. This stronger warming response of CH₄ exchanges during the non-growing season significantly increases the regional CH₄ exchange on the QTP. Our research reveals that CH₄ exchanges in the QTP have a higher warming sensitivity in non-growing seasons, which meanwhile are dominated by a larger warming rate than the annual average. The combined effects of these two factors will significantly alter the CH₄ source/sink on the QTP. Neglecting these impacts would lead to inaccurate estimations of CH₄ source/sink over the QTP under climate warming.