Abstract:From 2006 to 2007, a total number of 5 open top chamber (OTC) experiments were carried out in the subalpine meadow of northwestern Sichuan province, and the effects of the OTCs on temperature, soil water content, and plant biomass and community structure were examined. In the growing season, the mean soil temperatures at depth of 15cm and of ground surface and the air temperature at 30cm above ground were enhanced by 0.28℃, 0.46℃ and 1.4℃ by the OTC facility, respectively. However, soil water content in OTC was 5.49% lower than that in the control ones. With the warming and drying effect, plant biomass and community structure of the subalpine meadow changed significantly. The grass coverage (19.21%) and biomass (44.07g/m2) in the OTC were significantly higher than those in the control (8.04% and 18.1g/m2, respectively), while the forbs coverage (72.8%) and biomass（210.54g/m2）in OTC were significantly lower than those in the control (83.5% and 244.9 g/m2, respectively). Above- and below-ground plant fresh biomass were 265.17g/m2 and 1603.84 g/m2 in OTC, respectively, significantly lower than those in the control (272.63g/m2 and 1826.77g/m2, respectively). The distribution pattern of root biomass was also significantly changed by the OTCs. The proportion of root biomass increased at the depth of 0-10cm soil layer but decreased at the depth of 20-30cm soil layer, relative to those of the control.