Abstract: From 2006 to 2007, a total number of 5 open top chamber (OTC) experiments were carried out in the sub-alpine meadow of northwestern Sichuan province, and the effects of the OTCs on temperature, soil water content, plant biomass accumulation, and on carbon and nitrogen content were examined. In the growing season, the mean soil temperatures at depth of 15 cm and of ground surface and the air temperature at 30 cm above ground were enhanced by 0.28, 0.46 and 1.4℃, respectively by the OTC facility. However, soil water content in OTC was 5.49% lower than that in the control one. With the warming and drying effect, plant biomass accumulation, carbon and nitrogen content of the sub-alpine meadow obviously changed. The above-ground live biomass and below-ground root biomass both decreased in the OTC plots compared to the control plots during the growing season except that the above-ground live biomass increased a little in October. The C concentration of above-ground live in the OTC plots was higher than that in the control plots throughout the growing season, while the N concentration in the OTC plots was lower than that in the control plots. The C concentration of below-ground root in the OTC plots was also higher than that in the control plots throughout the growing season, and a significant difference was detected in August, while the N concentration in the OTC plots was also lower than that in the control plots. The C stock in the OTC plots increased compared to the control plots, and ranged from 0.90% to 5.65%, while the N stock in the OTC plots decreased compared to the control plots, and ranged from 0.40% to 1.28%.

Key words: Northwestern Sichuan, alpine meadow, open top chamber, experimental warming, carbon, nitrogen