Variation of CO₂ Flux of Alpine Wetland Ecosystem of Kobresia tibetica Wet Meadow in Lake Qinghai

Based on the eddy covariance system, variation of CO₂ flux of the alpine wetland ecosystem of Kobresia tibetica wet meadow in Lake Qinghai was characterized and its affecting factors analyzed. Results show that CO₂ flux in the ecosystem exhibits obvious characteristics of diurnal variation and monthly variation. During the vegetation growing season, net absorption of CO₂ was observed, with absorption peaks appearing between 12:30 and 15:00 daily, and the highest one reaching up to 0.42 mg·m^-2·s^-1, while net emission peaks appeared between 20:00 and 22:30, with the highest one being 0.24 mg·m^-2·s^-1. During the non-growing season, CO₂ flux varied slightly and was dominated with net emissions. In all the months of the non-growing season, except for November, CO₂ emissions were obviously higher in the day than in the night. The annual net ecosystem CO₂ exchange rate of 2015 was 54.55 g·m^-2 in the wet meadow wetland ecosystem, which obviously behaved as a carbon source. CO₂ emission path analysis shows that soil temperature, photosynthetically active radiation and saturated vapor pressure difference were the main factors controlling CO₂ flux in the ecosystem.