## 3 Results
### Land Use Change  
The analysis of the dynamic evolution of the spatial pattern of ecosystems around each reservoir revealed that the buffer zones were predominantly composed of grassland and cropland ecosystems, which together accounted for more than 80% of the total area on average, cropland ecosystems were primarily concentrated in areas near the rivers (Figure 5). Following the construction of the reservoirs, there was a gradual expansion of cropland, forest, barren, and water ecosystems over time, while grassland and barren ecosystems contracted (Figure 6). The dynamic rates of change in different ecosystems exhibited distinct patterns during two phases: the 10 years before and the 10 years after reservoir construction. Over the decade following construction, significant increases were observed in the areas of water bodies, impervious surfaces, and forest ecosystems, particularly in the LJ, KY, and HF reservoir regions. Notably, the area covered by water bodies expanded by 200%. This change is primarily attributed to watershed expansion and wetland restoration associated with reservoir impoundment. In the SZ reservoir area, the impervious surface increased dramatically by approximately 30 times, reflecting land use changes and accelerated urbanization resulting from reservoir construction. Additionally, forest cover increased substantially in most areas, especially in the LJ and KY regions, with the exception of the NN area, where the change was less pronounced. The rise in forested areas is closely linked to afforestation and  
Figure 4: Changes in the reservoir before and after the decade. ecological restoration projects around the reservoirs, particularly in regions implementing the \"returning farmland to forest\" policy. In contrast, barren and cropland areas showed more noticeable reductions. In most regions, both decreased after reservoir construction, with the LJ reservoir area experiencing the most significant reduction in barren land, decreasing by 34.7% (Figure 5). This change may be related to land reclamation, ecological restoration measures around the reservoir, and agricultural abandonment policies. The reduction in cropland was relatively minor, mainly due to the conversion of farmland to other land uses or inundation caused by the reservoir. Grassland changes were more complex and varied across regions. Although the overall change was relatively small, the expansion or degradation of grasslands in different areas was influenced by a combination of factors, including reservoir construction, climate change, and land use policies. The dynamic evolution of buffer zone ecosystems, both before and after the construction of each reservoir, was analyzed using the ecosystem transition matrix and chord diagrams. The results revealed significant spatial heterogeneity in ecosystem changes across the regions, with a substantial transformation of overall ecosystems, accounting for 5.2% to 12.5% of the total area in each region (Table 4). Reservoir construction had a profound impact on the surrounding ecological environment, particularly on land types such as water bodies, cropland, grassland, and forest, triggering complex ecological transformations. The most significant change during the ecosystem transition was the conversion of grassland to cropland, which represented the largest portion of the ecological shift (Figure 6). Other notable transition pathways included grassland to cropland, barren to grassland, and barren to impervious surfaces, together accounting for 93.2% of the total transition area. Additionally, the shift from cropland to forest, grassland, and shrubland was an important trend, with a total shift area of 15.5%. Analyzing these transformation paths revealed that grassland, cropland, and water ecosystems occupied the largest transition areas at all stages. In particular, ecological transitions between grassland, cropland, and water were prominent, with substantial transitions occurring at each stage.