Abstract: Carbon stock changes in terrestrial ecosystems are closely related to regional land use changes. It is important to predict carbon sources/sinks under different scenarios for land use management decisions and exploring carbon sink potential. Based on land use data in the upper reaches of Songhua River during 2000-2020, we used the CA-Markov model to predict the spatial pattern of land use under the status quo development scenario, economic development scenario, and ecological protection scenario, respectively. With modified carbon density data, we used the Carbon module of the InVEST model to assess carbon stock and changes in carbon sources and sinks in the upper reaches of the Songhua River for five periods during 2000 to 2050. The overall trend of carbon storage in the upper reaches of Songhua River from 2000 to 2020 was decreasing, with a total decrease of 168.4×10⁸ kg. During the 20year period, the decrease of forest area and the expansion of construction land and arable land were the main reasons for the decrease of carbon stocks. Under the status quo development scenario and the economic development scenario, carbon stocks will decrease greatly in 2030 and 2050. Under the ecological conservation scenario, carbon stocks will increase by 441.5×10⁸ and 658.1×10⁸ kg respectively compared to that in 2020, indicating that the land use pattern under this scenario has a strong carbon sequestration capacity. Our results provide a scientific basis for optimizing land use pattern and the sustainable development of the ecological services of carbon stocks in the upper reaches of Songhua River.

Key words: carbon stock, land use/cover change, CA-Markov model, InVEST model, carbon sink potential, the upper reaches of Songhua River