## 3 Results and Analysis
### Analysis of the Spatial and Temporal Evolution of Ecological Quality  
In order to further analyze the dynamic changes in the ecological environmental quality of the Nyingchi-Gongbo'gyamda section from 2012 to 2020, Table 6 presents the calculation of the difference in the modified remote sensing ecological index (MRSEI) for every two years. The difference values are categorized into five levels: significantly deteriorated (\(-2\)), deteriorated (\(-1\)), essentially unchanged (\(0\)), improved (\(+1\)), and significantly improved (\(+2\)). Figure 4 provides a visual representation of the proportions of each category and their changes over time. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Years**} & **The Ratio and** & **Significantly** & **Worse** & **Invariability** & **Improved** & **Significantly** \\  & **Area of Changes** & **Worse** & **Worse** & **Invariability** & **Improved** & **Improved** \\ \hline \multirow{3}{*}{2012–2014} & Change Area & 0.3125 & 545.375 & 990.0625 & 107.4375 & 0.8125 \\  & Percentage (\%) & 0.02 & 33.17 & 60.22 & 6.54 & 0.05 \\  & Change Area & 0 & 86.0625 & 1028.125 & 529.1875 & 0.625 \\
2014–2016 & (km\({}^{2}\)) & 0 & 5.23 & 62.54 & 32.19 & 0.04 \\  & Percentage (\%) & 1.125 & 199.25 & 1243.75 & 199.875 & 0 \\
2016–2018 & (km\({}^{2}\)) & 0.07 & 12.12 & 75.65 & 12.16 & 0 \\  & Change Area & & & & & \\
2018–2020 & (km\({}^{2}\)) & 0.4375 & 193.0625 & 1192.875 & 256.75 & 0.875 \\  & Percentage (\%) & 0.03 & 11.74 & 72.56 & 15.62 & 0.05 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Monitoring of the level of MRSEI changes from 2012 to 2020. Figure 4: Dynamic changes of the MRSEI in the Nyingchi–Gongbo’gyamda section of the Lhasa–Nyingchi Motorway from 2012 to 2020. Combining Table 7 and Figure 5, it can be observed that the ecological quality remained relatively stable across the four periods. The proportion of areas with deteriorated ecological quality was highest in the 2012-2014 period, accounting for 33.17% of the total area. The proportions of areas with unchanged and improved ecological quality were the lowest in the four periods. Clearly, the construction of the highway had a significant impact on the local ecological environmental quality. Figure 4 reflects that the regions with deteriorated ecological environments were mainly located along the road and at the edges of the study area. During the 2014-2016 period, only 5.23% of the area experienced deteriorated MRSEI, while the proportion of areas with improved ecological quality reached 32.19%. This improvement can be attributed to the restoration effects of ecological environment projects. Overall, the ecological quality of the study area showed a positive trend. From the MRSEI changes in the 2016-2018 period, it can be seen that the ecological environmental quality in the study area exhibited a rebound trend. Looking at Figure 2, it is evident that the areas with deteriorated ecological quality were mainly located along the road and at the edges of the study area, indicating the high ecological sensitivity and the difficulty of ecological restoration in the alpine region. The changes in the 2018-2020 period were similar to the previous period. Looking at the 2016-2018 period, it can be observed that the proportion of areas with unchanged ecological quality tended to stabilize. With the continued efforts in ecological governance, the transplanted vegetation can better adapt to the local climate and environment. Table 7 presents the calculation of the MRSEI difference between the year before road construction in 2012 and the fifth year after road implementation in 2020. It is evident that the overall ecological quality in the study area remained relatively stable from 2012 to 2020, with a value of 69.5%. The majority of this ecological quality was concentrated