Effects of grazing intensity on net ecosystem exchange of alpine meadow

Grazing played a significant role in the land usage and management of the Tibetan plateau. With the change in global climate, the impacts of different grazing intensity on net ecosystem exchange (NEE) of alpine meadow ecosystems in Qinghai-tibet plateau were different. In order to reveal the variations of gas exchange under different grazing intensities and provide the basic data for the carbon balance calculation of ecosystem, gas exchange under different grazing intensities were measured by infrared analyzer (Li-6400) with a transparent and closed chamber. With respect to NEE, the obvious seasonal changes were observed for ecosystem total respiration (Reco) and gross primary production (GPP). The varying curve of NEE performed as U-shaped and the varying curves of both Reco and GPP performed as single peak value wave. Values of NEE were negative from mid-May to mid-Sep, which indicated that alpine meadow ecosystem was carbon sink area at this stage. With 50% grazing intensity, NEE and GPP had the highest value which showed that moderate grazing was optimal to maintain higher level of carbon sinks for the Qinghai-Tibet plateau alpine meadow ecosystem.