Short-term responses of grass community in clear-cutting land of sub-alpine regions to simulated global warming,Western Sichuan

The responses of phenology,community structure and above-ground biomass of grass community in clear-cutting land of sub-alpine regions in Western Sichuan to simulated global warming were studied by using the open-top chamber(OTC) method.The results were shown as follows:mean air temperature was 2.2 ℃ higher in the OTC than in the control plot(CK) throughout the growing season and there was 0.8 ℃ difference in daily mean soil temperature at 5 cm below the soil surface between the OTC and the CK.Compared with those in the CK,constructive species(Artemisia subdigitata and Deyeuxia scabrescens) in the OTC showed earlier sprouting,pre-flowering bud,and florescence.However,they had later withering in the OTC than in the CK.Height,density and important value of each plant population responded differently(increase,decrease or no effects) to warming.The biodiversity index was slightly lower in the OTC than in the CK.Some changes in the community structure were observed.The above-ground biomass of Deyeuxia scabrescens and Artemisia subdigitata in the OTC increased by 46.3% and 42.3%,respectively.However,the above-ground biomass of Festuca sinensis and the other herbs in the OTC decreased,but not significant.Compared with those under ambient temperature,total above-ground biomass increased by 34.0% under elevated temperature.