Abstract: It has been demonstrated that climate change and associated warming has affected the soil organic carbon (SOC) in alpine meadows over past decades, but little is known about the coupling between climate change and grazing. In this research, an experiment incorporating controlled warming and grazing was used in conjunction with a denitrification-decomposition (DNDC) model to evaluate the contributions of climate change and grazing to changes in SOC in an alpine meadow ecosystem on the Tibetan Plateau. It was found that climate change influenced SOC negatively; while grazing intensity was an external factor that further modified SOC through trampling, defoliation and manure return. The model explained 63.4% of the observed change in SOC. Specifically, climate change (temperature and precipitation) was the major factor affecting SOC, and explained 61.9% of the variation in SOC. By contrast, grazing intensity explained 1.6% of the variation in SOC. These findings show that ongoing climate change and grazing can be expected to reduce SOC in alpine meadow ecosystems, potentially hindering their ability to provide ecosystem functions and services for human well being. Grassland ecosystem management should consider potential climate change effects to achieve sustainable development in this region.

Key words: climate change, grazing, DNDC model, soil organic carbon, alpine meadow