Objective The aims were to provide data support for the study of dual-carbon targets and ecological environmental protection in Xinjiang, as well as data support and scientific basis for the rational utilization and management of soils in the Southern Xinjiang region.

Method Based on the data of the second soil survey in Xinjiang in 1980 and the soil profile data in 2015, the variation characteristics of organic carbon (C) and inorganic C content in 0 ~ 100 cm soil layer of different soil types were compared and analyzed. The effects of climatic factors on them were discussed by means of variance analysis and correlation analysis.

Result The organic C contents of different soil types in the cultivated soil ranged from 1.13 g kg⁻¹ to 11.42 g kg⁻¹ with a change rate of 20.84%, and the inorganic C contents ranged from 8.84 g kg⁻¹ to 25.81 g kg⁻¹ with a change rate of −10.91%. The organic C contents of different soil types of non-tillage soils ranged from 1.18 g kg⁻¹ to 18.10 g kg⁻¹, with a change rate of 104.76%, and the inorganic C content ranged from 5.16 g kg⁻¹ to 24.52 g kg⁻¹, with a change rate of −3.35%. The average content of organicC in the South Xinjiang region during the two periods showed a highly significant negative correlation with temperature and a highly significant positive correlation with precipitation. The average content of inorganic C was opposite to that of organic C, which showed a positive correlation with temperature and a negative correlation with precipitation.

Conclusion These results showed that human factors had significant effects on soil C content. In the two periods, the organic C contents of most soil types were decreased with the increase of soil depth in the 0 ~ 100 cm soil layer, and the inorganic C content showed a trend of decreasing first and then increasing. In southern Xinjiang, temperature and precipitation were the main factors affecting the distribution of soil organic C content in the study area. The change of inorganic C content was more complex, and its change might also be affected by many other factors, which put forward more challenging and complex problems for future land management and C sink research.