Abstract: Terrestrial ecosystem carbon budget is a hot topic in the research on global climate change. The grassland of Qinghai-Tibet Plateau, which is sensitive to climate change, plays an important role in the regional carbon balance. However, there is great uncertainty in the estimation on the spatial-temporal pattern of carbon budget due to different methods and some other reasons. To some extent, climate warming results in the increase of vegetation primary productivity and biomass in the alpine meadow ecosystem, which may compensate the decomposition release of soil organic carbon. Hence, the Qinghai-Tibet Plateau grassland still functions as a carbon sink. The effects of human activities, such as overgrazing, on grassland ecosystems are very complex. Therefore, under the impacts of future climate change and human activities, how to distinguish the influence of climate change from that of human activities on ecosystems, and how to quantitatively assess carbon source / sink pattern, are a very interesting research field, but also a great challenge, especially on the plateau.

Key words: carbon budget, climate warming, grassland degradation, grassland ecosystem, Qinghai-Tibet Plateau