## 3 Results
### Prediction of Carbon Budget Scenarios under Different Vegetation Changes  
The CLUE-S model was employed to simulate and predict land use change in 2030 under different scenarios to further explore the influence of land use types on the carbon budget of vegetation ecosystems in the basin. The Kappa coefficient of the 2020 LUCC simulation results based on the 2000 and 2010 data was 0.83, which indicated that the model had high confidence in the LUCC simulation results in the Dongting Lake basin.  
Figure 9 displays the outcomes of various scenarios from the LUCC simulation. In general, driven by the demand of regional socioeconomic development, urban construction land showed an increasing trend in different scenarios, while cultivated land, forestland, and grassland continued to decrease (Table 1). However, the changes in each land type varied significantly under different scenarios. Under the natural development scenario, urban land continued to increase significantly (3467 km\({}^{2}\)). Land types such as cultivated land, forestland, and grassland continued to decrease by 985 km\({}^{2}\), 2561 km\({}^{2}\), and 757 km\({}^{2}\), respectively, while the water area continued to expand (975 km\({}^{2}\)). Under the ecological protection scenario, vegetated land types were effectively protected, with cultivated land, forestland, and grassland being 681 km\({}^{2}\), 421 km\({}^{2}\), and 82 km\({}^{2}\) higher than the natural growth scenario, respectively, while the expansion of urban land area (2257 km\({}^{2}\)) slowed down compared to the natural development scenario. In the priority economic development scenario, urban construction land expanded dramatically, increasing by 4182 km\({}^{2}\) compared to 2020, while all vegetation types of land showed a clear trend of decrease, with cultivated land, forestland, grassland, and other land types decreasing by 1428 km\({}^{2}\), 2755 km\({}^{2}\), and 807 km\({}^{2}\), respectively, compared to 2020.  
Figure 8: Comparison of carbon uptake effect of different vegetation types.  
The corresponding ecosystem carbon uptake characteristics were further analyzed based on the predicted results of the above LUCC scenarios (Figure 10, Table 2). Due to the increase in urban construction land and the continuous decrease in vegetation area, the ecosystem absorption under the three scenarios showed a downward trend. However, the vegetation carbon uptake in Dongting Lake Basin under the ecological simulation scenario was highest (7.83 \(\times\) 10\({}^{7}\) t C), which was the lowest decrease compared with 2020. However, the carbon uptake in the natural development scenario (7.80 \(\times\) 10\({}^{7}\) t C) and economic development scenario (7.78 \(\times\) 10\({}^{7}\) t C) was significantly reduced, which was 0.14 \(\times\) 10\({}^{7}\) t C and 0.16 \(\times\) 10\({}^{7}\) t C lower than those in 2020, respectively. Therefore, there is an urgent need to integrate socioeconomic and ecological environmental protection under the ecological protection scenario to promote collaborative and sustainable development in the future.  
Figure 9: Multi-scenario simulated land use map of Dong Ting Lake Basin in 2030: (**a**) land use in 2020, and (**b**) the natural development scenario, (**c**) the ecological protection priority scenario, and the (**d**) economic development priority scenario in 2030.