Environmental factors and near-surface air CO_2 concentration of swamp-meadow ecosystem on Qinghai-Tibetan Plateau in response to long-term experimental ecosystem warming

The responses of environmental factors to long-term experimental warming and their relationships with the near-surface air CO_2 concentration in the swamp meadow areas on the Qinghai-Tibetan Plateau were studied using OTCs systems with 3～5℃(OTC-80) and 1～2℃(OTC-40) elevated respectively.The results show that under the conditions in which the daily average air temperatures were 4.05℃and 2.13℃higher in the OTC-80 and OTC-40 chambers than those at the control points,respectively,the soil temperatures at the 5 cm depth in the OTC-80 and OTC-40 chambers were respectively 3.67℃and 1.65℃higher than those at the control points.However,the soil moistures at the 0～5 cm depth in the OTC-80 and OTC-40 chambers were 7.9%and 2.1%lower than those at the control points,respectively,and in the whole observation period,the CO_2 concentrations in the OTC-80 chambers were averagely 29.3μL/L higher than those at the control points and 9.8μL/L higher in the OTC-40 chambers than those at the control points.Air temperature rising led the climate warming and drying,and accelerated the soil carbon loss in the Qinghai-Tibetan Plateau,which plays a role of positive feedback to the global warming.Sensitivity analysis showed that air temperature,soil temperature and moisture at the 5 cm depth were the major environmental factors affecting the changes of the near-surface CO_2 concentrations,of which the 5 cm soil temperature was the most sensitive factor for the CO_2 concentrations change in the OTC-80 chambers and at the control points, and,relatively,0～5 cm soil moisture was the most sensitive factor for those in the OTC-40 chambers.