Abstract: The actual (NPP_A) and potential (NPP_P) net primary productivity in the area around Qinghai Lake were calculated based on MODIS NPP data, meteorological data and Thornthwaite model. The difference between NPP_P and NPP_A was used to quantify the impacts of human activities on net primary productivity (NPP_H). The temporal and spatial changes of grassland NPP_A, as well as the effects of climate change and human activities on grassland were analyzed. From 2000 to 2015, the average NPP_A was 176.93 g C·m^-2·a^-1. In addition, NPP_A exhibited a generally increasing trend between 2000 and 2015. In terms of spatial distribution, NPP_A increased gradually from west to east. 87.42% of the grasslands were restored, whereas only 12.58% were degraded between 2000 and 2015. For the effects of climate change and human activities on grassland restoration, the climate change, human activities and their combined effect of climate change and human activities contributed to 10.98%, 5.27% and 83.75%, respectively. For the effects of climate change and human activities on grassland degradation, the climate change, human activities and the combined effect of climate change and human activities contributed to 6.28%, 50.75%, and 42.97%, respectively. It is concluded that the grassland degradation in this area was mainly caused by irrational human activities, such as overgrazing, grassland reclamation and land cover change.

Key words: Chinese fir forest,  Phyllostachys pubescens forest, evergreen broad-leaved forest, throughfall, stemflow, interception.