[Effects of simulated rainfall enhancement on sediment CO2 flux in dry lakebed of Barkol Lake, China]. / 模拟增雨对巴里坤湖干涸湖底沉积物CO2通量的影响.

Understanding the responses of lake sediment carbon process to climate change is an important part of a comprehensive understanding of lake carbon budget. To explore the effects of future rainfall increase on sediment carbon flux, undisturbed sediment samples were collected from the bottom of dry lake Barikun in Hami, Xinjiang for the incubation experiment. Based on the increase rate of precipitation (4 mm·10 a-1) and the distribution characteristics of rainfall in the plant growing season in Hami, Xinjiang since 1960, five rainfall treatments were set (86 mm, T0; 94 mm, T1; 102 mm, T2; 110 mm, T3; 126 mm, T4) based on the rainfall in growing season of 2016 (86 mm). We analyzed the effects of rainfall increase on sediment CO2 flux. Results showed that compared with that before rainfall, the sediment CO2 flux increased after 1 day of rainfall in the study area. Compared with that during May to July, the CO2 flux of sediments in August to October decreased. There was no variation of CO2 accumulative emission among the T0-T3 treatments from May to October. However, the average CO2 emission rate under the T3 treatment (0.22 µmol·m-2·s-1) was significantly higher than that under the T4 treatment (0.14 µmol·m-2·s-1). All treatments showed CO2 sink at the first day of rainfall (1 d), with T4 treatment (-0.13 µmol·m-2·s-1) having the highest "carbon sink" capacity. After 1 day, the CO2 sink converted to CO2 source under the five rainfall treatments, with the CO2 emission rate under T3 treatment (0.34 µmol·m-2·s-1) being significantly higher than those under other treatments. Compared with May, the CO2 emission fluxes of T2-T4 treatments were significantly higher than those at the time from August to October. Under the condition with relatively stable temperature, the CO2 flux of sediments was significantly correlated with the sediment moisture and air humidity. In the next 60 years, the continuous increase of future rainfall may be an important factor promoting CO2 emission from lake sediment in arid regions, and thus affecting global warming.