​​Assessing environmental drivers of grassland cover change in the Fenhe River Basin using a random forest model

​​Under the background of environmental change, it is crucial to identify the characteristics and driving mechanisms of grassland cover change in the Fenhe River Basin to facilitate regional ecological restoration and effective grassland resource management. Taking 2000-2023 as the study period, this study used trend analysis and a land-use transition matrix to examine the spatiotemporal patterns of grassland cover change in the Fenhe River Basin. A random forest model combined with SHAP analysis was applied to identify and compare the main environmental driving factors. The results showed a clear overall decline in grassland cover from 2000 to 2023, with a spatial pattern of gradual decrease from north to south. The decline was most pronounced in the downstream region, followed by the midstream and upstream regions. Among the environmental factors, evapotranspiration (ET) was the most important influence on grassland cover change, showing the highest importance scores at both the basin scale and within all subregions. These scores were significantly higher than those of the other factors, with more prominent effects in the midstream and downstream areas. Precipitation and temperature also significantly affected grassland cover change and exhibited marked spatial heterogeneity. Temperature played a stronger role than precipitation in the upstream region, whereas precipitation was more influential in the midstream and downstream regions. The effects of elevation and slope were generally stable, reflecting their background and constraining roles. Furthermore, the SHAP analysis indicated that the relationships between environmental factors and grassland cover change were not simply linear. ET generally showed a strong positive contribution, while precipitation and temperature displayed certain threshold effects. Slope and elevation imposed stable topographic constraints. These findings provide a scientific basis for grassland conservation, ecological restoration, and integrated basin management in the Fenhe River Basin.