Objective The purpose of this paper was to scientifically measure, assess and predict the carbon sink effect under land use changes, in order to efficiently evaluate the ecological benefits of cities under different development policy scenarios.

Method This article took Hohhot City as an example, the soil organic carbon (C) contents of different land use were assessed through field investigation, sampling and laboratory measurement. Based on the FLUS model and InVEST model, the current trend development scenario, reasonable development and construction scenario and "dual carbon" target development scenario were evaluated for the land use status, C storage, and C sink value from 2000 to 2030.

Result ① The land use types in Hohhot City were mainly farmland and grassland, and the land use structure has changed significantly in the past 20 years. Land use transfer mainly occurred between farmland and construction land. ② In 2000, 2010 and 2020, the C storage of the urban ecosystem in the third phase of Hohhot City showed a clustering distribution influenced by land use types, and the overall C storage showed a downward trend. Due to the conversion of land use types, the C storage decreased by 4.97 × 10⁶ t. ③ The study was based on the historical land use evolution law and simulated different policy development scenarios for the year 2030. It is found that the current trend development scenario showed the most significant decrease in C storage. Due to increased protection efforts for high C density land types, urban C sequestration capacity has been improved under the "dual carbon" target scenario. ④ Among the three development scenarios, the "dual carbon" target development scenario had the highest C sink value, with an average annual net C value of 24 million yuan per year.

Conclusion The future construction of a high C sequestration spatial pattern in cities should comprehensively consider the ecological background and economic benefits of the region, strengthen the intensive and economical use of core construction land, and promote sustainable land use and C sequestration management.