Abstract: By using MODIS remote sensing data, this paper studied the spatiotemporal distribution and variation characteristics of vegetation net primary productivity (NPP) and their relationships with climate change and human activity in the Shiyang River basin of Northwest China in 2000-2010, with the human effect model of NPP established. In 2000-2010, the total vegetation NPP in the basin decreased after an initial increase, with the peak in 2002 and a periodical fluctuation in the decreasing process. Overall, the NPP had a significant positive correlation with precipitation, but less correlation with air temperature; whereas in some areas, the NPP had significant correlation with precipitation, and also, stronger correlation with air temperature. The related division lines for the annual precipitation were 380 mm and 170 mm. In the areas with the annual precipitation greater than 380 mm, air temperature was the dominant factor affecting the NPP; in the areas where the annual precipitation was 170-380 mm, precipitation was the dominant factor; and in the areas with the annual precipitation less than 170 mm, precipitation and human activity were the primary factors.  Under the effects of human activity, the annual increment of the NPP in the basin in 2000-2010 was averagely 2353.86 g C·m^-2·a^-1, suggesting that the vegetation coverage in the basin was improved to some extent after the eco-environment management project was implemented. From the view point of vegetation type, grassland was most acutely positively and negatively affected human activity, cropland was also very obviously affected by human activity, and the cropland NPP was increased by the improvement of cultivation and management measures, whereas the Gobi, saline and alkaline land, sand land, and forestland in the oasis edges were basically positively affected by human activity, their vegetation coverage and quality being somewhat increased.

Key words: Castanea mollissima plantation, CO₂ efflux, biochar, water-soluble organic carbon (WSOC), microbial biomass carbon (MBC).