Responses of CO2 and CH4 in the alpine wetlands of the Tibetan Plateau to warming and nitrogen and phosphorus additions†

Wetland ecosystems store large amounts of carbon, and CO₂ and CH₄ fluxes from this ecosystem receive the double impact of climate change and human activities. Nonetheless, research on how multi-gradient warming and nitrogen and phosphorus additions affect these wetland greenhouse gas emissions is still limited, particularly in alpine wetland ecosystems. Therefore, we conducted a field experiment on the Tibetan Plateau wetlands, investigating the effects of warming and nitrogen and phosphorus additions on the CO₂ and CH₄ fluxes in alpine wetlands. Results indicated that warming enhanced the CO₂ absorption and CH₄ emission in the alpine meadow ecosystem, possibly related to changes in plant growth and microbial activity induced by warming, while we noticed that the promotion of CO₂ uptake weakened with the increase in the magnitude of warming, suggesting that there may be a temperature threshold beyond which the ecosystem's capacity for carbon sequestration may be reduced. Nitrogen addition increased CH₄ emission, with the effect on CO₂ absorption shifting from inhibition to enhancement as the amount of applied nitrogen or phosphorus increased. The interaction between warming and nitrogen and phosphorus additions further influenced CH₄ emission, exhibiting a synergistic enhancement effect. This study deepens our understanding of the greenhouse gas responses of alpine wetland ecosystems to warming and nitrogen and phosphorus additions, which is significant for predicting and managing ecosystem carbon balance under global change.