Soil-type-dependent changes in topsoil organic carbon storage of cultivated lands in China

Cultivated soil carbon storage is critical for sustainable agricultural development and climate change mitigation; however, the differential responses of specific soil types to carbon storage at the national scale remain poorly quantified. We assessed spatiotemporal patterns of soil organic carbon (SOC) storage across major cultivated soil types in China from 2000 to 2020 using data from the Harmonised World Soil Database and China's High-Resolution National Soil Information Network. Notably, SOC storage in cultivated soils showed a net decline (-666 Tg) during the study period, with 60% of the reduction occurring in unchanged cultivated land (UCL), highlighting that carbon losses occurred even without land-use conversion. Anthrosols in UCL experienced severe SOC density declines in the Qinghai Tibet Plateau, Northern arid and semiarid region, and Sichuan Basin. These findings highlight the need for targeted carbon management strategies that prioritize soil types with high sequestration potential (Luvisols and Fluvisols) while addressing vulnerability in high-risk soil types (particularly Anthrosols and other degraded soils).