5 Conclusion
In this study, we found that SIC stocks increased from 0 to 300 cm after afforestation in arid semi-arid sandy land, indicating that the afforestation of sandy land increased the soil carbon sequestration capacity. 0-300 cm SIC increased continuously (insignificantly) with stand age, while the difference between MS and other stand age stages of soil inorganic carbon was significant. Afforestation in semi-arid sandy areas not only increased SIC storage but also significantly changed the profile distribution characteristics of SIC. Soil moisture had a significant effect on SIC in all layers, while pH had a significant effect on SIC in deep layers. The decreasing rate of inorganic carbon fixation with increasing stand age implies that the rate of soil inorganic carbon fixation is not a constant value, and it is necessary to quantify the temporal pattern of SIC changes to accurately estimate the dynamics of regional SIC stocks. Our study also highlights the importance of deep SIC stocks in semi-arid regions in soil carbon sink estimation.
Funding: This study was supported by the Major Science and Technology Project in Inner Mongolia Autonomous region of China (No. Zdzx2018057), the Innovation Cross Team Project of Chinese Academy of Sciences, CAS (No. JCTD-2019-19), Transformation Projects of Scientific and Technological Achievements in Inner Mongolia Autonomous region of China (No. 2021CG0046), and Groundwater environmental evolution in Minqin Basin under the influence of climate change and human activities (No. 23JRRA611).
Data availability statement: The original contributions presented in the study are 404 included in the article/Supplementary Material. Further inquiries can be directed to the 405 corresponding author.