Abstract: [Purposes]To address the limited understanding of ecological vulnerability,spatio-temporal variations in ecological environmental quality,and their driving mechanisms in the Altay region,this study systematically investigates the spatio-temporal dynamics of ecological environmental quality and its influencing factors.[Methods]First,multi-period MODIS data were acquired from the Google Earth Engine(GEE)platform,and the remote sensing ecological index (RSEI)was constructed using principal component analysis to comprehensively characterize regional ecological environmental quality.Then,Sen's slope estimator,the Mann-Kendall test,and the coefficient of variation (CV)were applied to identify spatiotemporal trends and stability patterns.Finally,an XGBoost model combined with SHAP was employed to quantify spatial heterogeneity and determine the dominant driving factors.[Findings]The results indicate that：① The mean RSEI exhibited an overall fluctuating downward trend over the past 20 years,with ecological environmental quality mainly classified as “poor” and “relatively poor，” and a spatial pattern characterized by better conditions in the north than in the south；②Approximately 67% of the region experienced a declining trend,while only 1.2% showed significant improvement,and 87.3% of the area displayed low or relatively low variability,indicating generally high stability； ③Evapotranspiration and slope were the dominant factors governing the spatial heterogeneity of ecological environmental quality.[Conclusions]These findings provide scientific support for ecological conservation and zonal management strategies in the Altay region．

Key words: Altay region, Google Earth Engine platform, remote sensing ecological index, XGBoost model