Abstract: Clarifying the impacts of climate change and human activities on net primary productivity (NPP) is important for regional environmental management and sustainable development. Based on data of NPP, land use type and meteorology, we analyzed the spatial and temporal variations of actual NPP (NPPA) in Fukang from 2001 to 2019, and further distinguished the impacts of climate change and human activities on NPPA in altitudinal natural belts. The results showed that the multi-year average of NPPA in Fukang was 100.56 g C·m^-2·a^-1, with a significant increasing trend (P<0.05). The areas with high and rapidly rising NPPA were located in farmlands and forests. The multi-year average of NPPA of different land use types differed significantly (P<0.05), with the highest in forests (335.77 g C·m^-2·a^-1) and the lowest in deserts (19.27 g C·m^-2·a^-1). NPPA of forests, grasslands, and built-up lands showed a significant increasing trend (P<0.05). After subdividing NPPA into potential NPP (NPPP) and NPP caused by human activities (NPPH), we found that the multi-year average of NPPP in Fukang was 284.06 g C·m^-2·a^-1, with insignificant interannual variation (P>0.05). In contrast, the multi-year average of NPPH was 183.50 g C·m^-2·a^-1, with a trend of significant decline (P<0.05). There were differences in the impacts of climate change and human activities on different natural belts, with climate change contributing most to NPPA in the steppe belt (NPPP=353.05 g C·m^-2·a^-1) and NPPA in the desert belt being most influenced by human activities (NPPH=201.94 g C·m^-2·a^-1). For the impact factors of NPP_A, precipitation and temperature can indirectly contribute to NPP_A by enhancing NPP_P, while beneficial human activities indirectly contribute to NPP_A by reducing NPP_H.

Key words: path analysis, CASA model, net primary productivity, temperature, precipitation.