[Land Use Optimization and Carbon Reserve Assessment in the Shiyang River Basin]

Studying the response relationship and spatial distribution characteristics of carbon reserve and land use change and predicting the change trend of carbon reserve caused by the change of land use type in the future can provide some reference for watershed policy formulation, land use structure adjustment, and the realization of the "two-carbon" goal. Based on the land use data from 2000, 2010, and 2020, the InVEST model was used to calculate carbon reserves and analyze the change characteristics and to simulate the land use change and its impact on carbon reserves in natural development, urban development, and ecological protection in 2030 with the help of the PLUS model. The study found that ① the main land types in the Shiyang River Basin from 2000 to 2020 were cultivated land, grassland, and unused land. The area of cultivated land, water area, and construction land in the Shiyang River Basin showed a significant increasing trend, and the construction land area increased the most. ② In the natural development scenario of 2030, cultivated land, water area, and construction all increased by 6.15%, 9.56%, and 29.9%, respectively. In the urban development scenario, the area of construction land increased the most. Compared with that in the other two scenarios, the area of forest land and grassland increased in the ecological protection scenarios. ③ The carbon reserves of the Shiyang River Basin from 2000 to 2020 showed a steady increase, with an overall increase of 0.035×10⁸ t. The increased carbon reserves were mainly due to the increase in cultivated land area. ④ In 2030, the carbon reserves of the Shiyang River Basin showed an increasing trend in all three scenarios. The carbon reserves in the three scenarios were 5.65×10⁸, 5.64×10⁸,and 5.73×10⁸ t, respectively, with the largest increase in carbon reserves in the ecological conservation scenario, mainly due to the increase in grassland and woodland. The results showed that the expansion of construction land was the main cause of the loss of carbon reserves. If effective ecological protection measures are taken, the carbon reserves in the Shiyang River Basin will be improved, and the problem of the loss of carbon reserves caused by economic development can be solved.