The distribution and driving mechanism of soil inorganic carbon in semi-arid and arid areas: A case study of Alxa region in China

Soil inorganic carbon (SIC) is a large reservoir in semi-arid and arid regions in the form of soil carbonates, but its specific distribution and storage at spatial scales are not clear. The Alxa region is a typical semi-arid and arid area, and we revealed the spatial distribution of SIC in the 0–300 cm soil layer and the accumulation and driving mechanism of SIC in semi-arid and arid areas through soil survey sampling in the Alxa region. In the Alxa region, the SIC content in the 0–300 cm soil layer increased with the deepening of the soil profile. Soil inorganic carbon density (SICD) is 8.15 kg⋅m⁻² in the 0–100 cm soil layer, and 18.96 kg⋅m⁻² in the 100–300 cm soil layer. SICD showed no obvious spatial variation trend in the shallow layer (0–150 cm), and showed an increasing trend from southeast to northwest in the deep layer (150–300 cm). With the increase of soil depth, the degree of influence of random factors on the spatial variation of SICD decreased continuously, while the degree of influence of structural factors on the spatial variation of SICD increased continuously. By analyzing the influencing factors and driving mechanisms of SIC, it can be seen that the atmosphere–vegetation–soil water–sedimentation carbon transfer system under arid conditions is the main mechanism and pathway of SIC accumulation in semi-arid and arid regions.