Abstract: Kurustai grassland is important for agriculture and animal husbandry development in the Tacheng region of Xinjiang, China. To fighting against the increasingly prominent environmental problems such as severe grassland degradation, desertification, and salinization, China has implemented a series of ecological restoration projects to improve grassland environment. Timely, objective, and quantitative evaluations of spatial and temporal variations in ecological environment quality are important for the implementation of environmental protection and restoration projects and policymaking. Using Google Earth Engine (GEE), a remote sensingbased ecological index (RSEI) was constructed based on highquality Landsat images in 2009, 2012, 2015, 2018, and 2021, to assess spatiotemporal variations and spatial clustering patterns of environment quality in Kurustai grassland. The results showed that: (1) The mean value of RSEI increased from 0.294 to 0.324 during 2009-2021, indicating a fluctuating upward trend for the overall environmental quality of the Kurustai grassland. (2) Spatially, the areas with poor and fair environment quality levels were distributed in the western, northwestern, and southwestern regions of Kurustai grassland at relatively low elevations, whereas those with good and excellent environment quality levels were primarily concentrated in the central and eastern regions with high forest cover and less human activities at high elevations. (3) From 2009 to 2021, the global Moran’s I values of RSEI were 0.508-0.687, indicating a positive correlation with the spatial distribution of environment. The local spatial autocorrelation clustering map of RSEI showed that high-high (H-H) clustering areas were primarily distributed in the central region with low elevation, whereas low-low (L-L) clustering areas were in the southwest and northwest parts of the region with sparse vegetation and high elevation.

Key words: RSEI, environment quality, spatial autocorrelation, Kurustai grassland, ecological restoration project.