5. Conclusion
We found that vegetation restoration in dryland areas served as a carbon sink. The annual NEP ranged from 34.70 to 168.30 gC m-2 yr-1 during stable periods (2009-2021), with a mean value of 91.61 ± 36.17 gC m-2 yr-1. A positive NEP value indicates that vegetation restoration serves as a carbon sink. The change in climate did not directly contribute to the increase in NEP, as there was no significant increase in the annual temperature and precipitation. However, the start, end, and duration of net carbon uptake showed a significant increasing trend which led to a significant increase in annual GEP and an insignificant increase in Re. The change in the net carbon uptake period played a role in the increase in NEP. The trend of increasing NEP was most pronounced in spring. Higher spring temperatures and an earlier onset of net carbon uptake increase spring NEP, where summer and autumn NEP are mainly influenced by precipitation. The end of autumn net carbon uptake had no significant effect on autumn NEP.