Abstract: Liuba County, the hinterland of the southern foot of the Qinling Mountains, was selected for this case study. Based on Landsat 5 TM and Landsat 8 OLI images, the remote-sensing ecological index (RSEI) was constructed to analyze the spatio-temporal variations of the quality of ecological environment in Liuba County from 1990 to 2020. The geographical detector model was used to attribute the spatial variation of the quality of ecological environment. The results show that, temporally, from 1990 to 2003, the quality of ecological environment in Liuba County showed a large area of slight deterioration, and the area where RSEI grade decreased by one level accounted for 96.47% of the total degraded area. From 2003 to 2020, the quality of ecological environment in Liuba County showed a large area of minor improvement, and the area where RSEI grade increased by one level accounted for 89.73% of the total improved area. Spatially, the overall distribution of RSEI grade in Liuba County was medium or better. Areas with poor and inferior RSEI grades were mainly distributed in the bare land at western Liuhou Town and the residential areas in the hills, accounting for less proportion of the study area. The dominant driving factors of the quality of ecological environment in Liuba County were elevation, annual average temperature, and agricultural production. Annual precipitation and roads were the secondary factors. Natural factors and human factors had combined effects on the ecological environment of Liuba County. Human factors such as agricultural production, roads and population pressure were still the critical points to concern for future ecological construction in Liuba County.

Key words: remote sensing based ecological index (RSEI), geographical detector model (GDM), quality of ecological environment, Qinling Mountains of Shaanxi Province