The effect of afforestation on inorganic carbon in soils of arid and semi-arid lands of northwest China

Abstract Alxa is a region with severe land desertification and extreme ecological fragility in China. The plantation in the area has effectively curbed the desertification of the local land. However, Studies on soil inorganic carbon（SIC）dynamics after sandy land afforestation are still relatively few. Understanding SIC profiles' distribution and stock changes after afforestation is essential for assessing regional, continental, and global soil carbon sink potential. Using 5, 11, 22, and 46 years of Haloxylon ammodendron (H. ammodendron) plantations and control sands (MS) in the Alxa region, we studied the variation characteristics of SIC with increasing stand age from 0 to 300 cm. Within the 0-300 cm soil layer, SIC storage increased significantly after afforestation, with 46yrs increasing by 6.52 kg m-2 compared to MS. SIC sequestration rate (CSR) decreased with increasing stand age, in the order of 5yrs（0.054 kg m-2 yr-1）＞11yrs（0.025 kg m-2 yr-1）＞22yrs（0.016 kg m-2 yr-1）＞46yrs（0.009 kg m-2 yr-1）. The 100~300 cm SIC storage accounts for over 60% of the SIC pool. Soil carbon pool estimation will be largely underestimated if only the shallow SIC is considered.