Effect of warming on the carbon flux of the alpine wetland on the Qinghai–Tibet Plateau

Abstract

Under the scenario of global warming, the response of greenhouse gas emissions from alpine wetlands remains unclear. In this study, fluxes of CO 2 and CH 4 were measured during daytime for the microtopographic features of hollows and hummocks in a wetland in the Tibetan Plateau under two elevated temperatures, increments of ∼1°C (T1 treatment) and ∼2°C (T2 treatment), during the growing season in 2019. The results showed that warming significantly increased the cumulative net ecosystem CO 2 exchanges (NEE) for both microtopographic features in the wetland compared to the control due to a combination of the increased gross primary production (GPP) with an increase in ecosystem respiration (ER). Similarly, warming also increased cumulative CH 4 emission significantly. The effect was stronger for T2 than that for T1 for all component fluxes (GPP, ER, NEE, and CH 4 ). Generally, NEE and CH 4 fluxes both rose at first and then decreased. NEE peaked at the end of July for both hollows and hummocks, while CH 4 emissions peaked in the middle of August. The cumulative CH 4 emissions from the hummocks were significantly higher than those of the hollows, and CH 4 emissions under illumination were significantly higher than those in darkness, which may be caused by the irradiation-sensitive vegetable internal convective gas transport system which diffuses CH 4 from the pedosphere. This study revealed that warming strengthened the function of the CO 2 sink but also increased CH 4 emissions from the alpine wetlands on the Qinghai–Tibet Plateau.