The effects of afforestation on soil water balance and carbon storage have been well-documented. However, the impact of artificial afforestation in arid and semi-arid regions on soil moisture, carbon storage, and their interrelationship remains unclear. This study aims to provide a comprehensive understanding of the process of soil water carbon change and mutual feedback mechanism after plantation in arid and semi-arid areas. We selected four different stand ages (5yrs, 11yrs, 22yrs, and 46yrs) of planted Haloxylon ammodendron (HA) forests in the Alaska Plateau. Nearby mobile sand (MS) was used as a control to study the changes in soil moisture content (SWC) and soil organic (SOC) and inorganic carbon (SIC) in the 0-300cm soil layer after afforestation, as well as the coupling relationship between soil water and carbon. The results showed that afforestation significantly increased SOC and SIC stocks relative to mobile sand MS. The SIC increased by 4.02 kg m-2, 4.12 kg m-2, 5.12 kg m-2 and 6.52 kg m-2 for 5yrs, 11yrs, 22yrs and 46yrs, respectively, compared to MS. SOC increased by 2.55 kg m-2, 2.91 kg m-2, 3.53 kg m-2, and 4.05 kg m-2, respectively, compared to MS. However, afforestation also resulted in a significant reduction in deep SWC and a greater soil water deficit (SMD). Mean SWC values were reduced by 0.48%, 1.37%, 1.56%, and 4.00% for 5yrs, 11yrs, 22yrs, and 46yrs, respectively, compared to MS. There was a significant negative correlation between deep SWC and SOC and SIC, i.e., the increase of soil carbon pool by sand afforestation was actually at the cost of the decrease of soil moisture. We recommend appropriate harvest management measures on forest land to reduce SWC losses while also promoting sustainable forest land development
