This dataset is clipped from the Northwest China soil organic carbon density dataset and a total of 1,490 sampling points of actual soil measurements in the Northwest China were used to produce the product, with the following main sources of data:

Projects undertaken by this research team：

The National Natural Science Foundation of China (NSFC) project "Research on the variation pattern and mechanism of soil organic carbon along the gradient in Qilian Mountain" (41771252), "Investigation of Ecohydrological Sample Strips in the Heihe River Basin" (91025002)、"Soil Carbon Simulation in Typical Ecosystems of Arid Inland River Basins" (31270482); Major Project in Gansu Province: "Research on the Interaction between Ecosystems and Hydrological Processes in Qilian Mountains and Their Adaptation to Climate Change" (18JR4RA002), The Science and Technology Innovation Project of Gansu Provincial Forestry and Grassland Bureau, "Research on Ecological Management Effectiveness Assessment of Qilian Mountain National Park (Gansu Area)" (GYCX[2020]01), Gansu Provincial Science and Technology Plan Funding Project "Gansu Qilian Mountain Ecological Environment Research Centre" ( 18JR2RA026) and other project data.

Raw Soil Profile Data, Literature Integration Data published by National Cryosphere Desert Data Centre and National Tibetan Plateau Data Center (Xu et al., 2018 DOI:10.1038/s41598-018-20764-9), WoSIS Soil Profile Database published by International Soil Reference and Information (ISRIC, https:// www.isric.org/explore/wosis), among others.

The original data were quality controlled by removing sampling points with less than 0.001 latitude and longitude positioning accuracy, and abnormal values where the soil organic carbon content deviated significantly from the environmental background.

Based on the 'Scorpan' (Soils, Climate, Organisms, Relief, Parent material, Age, Geographic position) framework, the spatial distribution of soil organic carbon density at 30m resolution in the 0-100 cm soil layer was simulated using the Digital Soil Mapping (DSM) method and a tile structure-based algorithm.

The forecasting method is mainly based on the Extreme Gradient Boosting algorithm in machine learning, with environmental covariate data including: Landsat8 OLI multispectral imagery, Sentinel-1 radar imagery, raster data such as temperature, precipitation, radiation, topography, vegetation indices, and location.

The digital soil mapping framework is constructed in R. In order to reduce memory usage and increase computing speed, the entire Qilian Mountains region is divided into 33 sub-regions (regions) of 150km×150km, and a mapping process based on tiles (tile size: 15km×15km) and parallel computing is constructed within each sub-region. The modelling is repeated by the bootstrap method for each. The spatial modelling of bootstrap samples is carried out to obtain the frequency distribution of the modelling results, and the modelling uncertainty is expressed as standard deviation (sd).