Abstract: Net primary productivity (NPP) in arid and semi-arid areas dominates the inter-annual variation (IAV) of global NPP. However, the NPP-IAV and its driving mechanisms in these areas remain unknown. Here, we estimated NPP in Hexi Corridor during 2002-2017 using the CASA model, calculated the change of NPP-IAV based on the formula of anomaly flux, and quantitatively estimated the contributions of spatial-temporal and climate factors to NPP-IAV. The results showed that NPP in Hexi Corridor increased from 2002 to 2017, and vegetation was growing well. During the study period, NPPIAV showed a variation pattern from negative to positive. The NPP-IAV of Hexi Corridor was affected by warm-dry and cold-wet climate. The former climate condition controlled the largest area (51.01%) and contributed only 15.38% to NPP-IAV. In contrast, the cold-wet condition contributed the most to NPP-IAV (48.68%), though only accounted for 23.67% of the area. The warm-dry climate dominated the distribution pattern of NPP in the Hexi Corridor, with the coldwet climate dominating the NPPIAV. NPP in July contributed the most and that in March contributed the least to IAV. Grasslands dominated the NPP-IAV in the Hexi Corridor. The total NPP in desert was the lowest, but its contribution to NPP-IAV was more than that of forests. Therefore, it is predicted that the vegetation NPP-IAV will be further intensified with climate warming in the arid region of northwest China in the future.

Key words: net primary productivity, inter-annual variation, spatial-temporal contribution, climate driving, Hexi Corridor.