## 4 Conclusions  
This study mainly utilized MODIS data from the GEE platform and combined it with the characteristics of the Xizang region. By introducing a combination weighting method based on GT, the RSEI was improved to evaluate the ecological environmental quality of the Lhasa-Nyingchi Motorway's Nyingchi to Gongbo'gyamda section. The main conclusions are as follows:  
1. The overall ecological environmental quality of the Nyingchi to Gongbo'gyamda section has significant regional differences. The quality of the ecological environment \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & & \multicolumn{4}{c}{**2012**} \\ \cline{2-6}  & Level & Excellent & Good & Moderate & Fair & Poor \\  & Excellent & 33.35 & 12.88 & 0.95 & 0.21 & 0.18 \\  & Good & 65.39 & 75.98 & 32.10 & 4.57 & 1.95 \\  & Moderate & 1.27 & 10.36 & 54.22 & 29.60 & 8.31 \\  & Fair & 0.00 & 0.71 & 11.57 & 49.21 & 45.36 \\  & Poor & 0.00 & 0.07 & 1.17 & 16.40 & 44.21 \\  & Rate of change & 9.62 & \(-\)12.32 & 10.36 & 13.99 & \(-\)7.25 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Level transfer matrix of the MRSEI for the Nyingchi-Gongbo’gyamda section of the Lhasa-Nyingchi Motorway from 2012 to 2020 (%). decreases from east to west. In the central and eastern sections, the ecological environmental quality is better on the southern side compared to the northern side. The areas with better ecological quality are mainly located in the southeastern part, while areas with poor, fair, and moderate ecological quality are mainly located in the roadside areas and the peripheral regions of the central and western sections. 2. During the process of highway construction and operation, the ecological environmental quality shows a trend of \"initial decline, subsequent improvement, and then a stair-step increase\". The construction of the highway is the primary driver of ecological degradation in the study area, significantly reducing its ecological environmental quality. However, short-term ecological restoration and compensation efforts have allowed for the recovery of the ecological environmental quality, followed by a stair-step growth. This is mainly due to the strong ecological sensitivity of the Xizang region, as well as its unique geographical and climatic characteristics such as high altitude and large diurnal temperature differences, which increase the difficulty of ecological restoration. 3. The ecological environmental quality in the study area from 2012 to 2020 mainly remained unchanged; with the area of improved ecological quality being greater than the degraded area, the ecological restoration project of the Llasa-Nyingchi Motorway has shown significant effectiveness. The unchanged rate of ecological environmental quality is 69.5%, mainly occurring in good and moderate levels. In the area where the quality of the ecological environment has changed, there were significant improvements in all four levels of ecological quality: poor, fair, moderate, and good, mainly occurring in the middle and western sections. The types of ecological quality degradation mainly transformed from excellent to good and good to moderate, with the transformation being more pronounced in the central and eastern parts of the study area. Overall, the assessment results validate the importance of ecological restoration projects. However, it is worth noting that due to the high cloud cover in the Nyingchi region from July to September, both Landsat and Sentinel data were not available for use in this study. As a result, the assessment primarily relied on MODIS imagery data and lacked consideration of factors such as meteorology and economic development. In future research, the focus will be on integrating high-temporal-resolution land satellite data, meteorological data, and other relevant factors for a more in-depth analysis. This aims to further enhance the effectiveness of ecological restoration in the Xizang region. Methodology, P.J. ; Data curation, J.Y. and S.S.; Writing--original draft, X.W. ; Project administration, X.H. ; Funding acquisition, Q.L.