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Accurate assessment of soil C storage patterns and control factors on a regional and global scale is essential for predicting and mitigating soil C feedback to global environmental change. We used soil samples collected in the Shiyang River Basin in 2018, combined with remote sensing data, climate and meteorological data, watershed hydrological data, and soil physical and chemical properties to discuss the change characteristics and influencing factors of soil organic carbon (SOC) under different soil depths in the Shiyang River Basin in an arid area and analyze the storage model and carbon sequestration potential of soil organic carbon in different geomorphic units. The research results show that, (1) in spatial distribution, the SOC content in the Shiyang River Basin shows an obvious regional difference, and the average content of SOC in the oasis area in the middle reaches significantly higher than that in the mountain area in the upstream and desert area in the downstream. In vertical distribution, the content of SOC in the whole watershed decreases with the soil depth increase. (2) Soil carbon sequestration potential decreased with the increase in soil depth, but there were regional differences. The Oasis area in the middle reaches of the Shiyang River Basin is a high-potential area. In contrast, most of the upper mountain areas and the lower reaches of the desert area are low-potential areas. Environmental factors such as vegetation cover, meteorological factors, and physical and chemical properties of soil are important factors that promote the spatial variability of SOC content. The decisive effect of environmental factors on the SOC content is most significant in the surface layer 0–20 cm. [ABSTRACT FROM AUTHOR]

[Display omitted] • Grassland degradation is the main reason for the decline in carbon storage. • The carbon storage of farmland has increased significantly. • The risk of carbon storage reduction in the future is still high. The carbon storage of terrestrial ecosystems is closely related to global climate change. Therefore, assessing the impact of land-use changes on carbon storage is instructive to reduce global carbon emissions. Taking an arid region in northwest China as an example, this paper analyzed the land-use changes in arid region from 1980 to 2015. It used the CA-Markov model to predict the land-use pattern from 2020 to 2050, the carbon storage and sequestration module in Integrated Valuation of Ecosystem Services and Tradeoffs (Invest) mode to assess and predict ecosystem carbon storage over the past 35 years and in the next 30 years and discusses the impact of land-use changes on the carbon storage of terrestrial ecosystems. The results showed that: (1) The high-value areas of carbon storage in arid region were primarily concentrated in grassland, forests and farmland, and the low-value areas of carbon storage were mainly in desert areas. (2) The carbon storage in arid region showed a downward trend. From 1980 to 2015, the carbon reserves of terrestrial ecosystems in arid region decreased by 90.95 Tg, and the net loss of carbon reserves from 2020 to 2050 was 14.72 Tg. Grassland degradation was the main reason for the reduction of carbon storage in arid region. (3) The carbon storage of farmland had increased significantly, but the expansion of farmland dominated by high carbon density grassland, wetland and forest, had reduced the overall carbon storage of the arid region. [ABSTRACT FROM AUTHOR]