## 3 Results  
### Single Factor Analysis  
#### 3.1.1 Natural Environmental Factors  
1. Mean annual temperature. The mean annual temperature in the Tumen River Basin ranges from \(-0.9\,\mathrm{\SIUnitSymbolCelsius}\) to \(6.7\,\mathrm{\SIUnitSymbolCelsius}\), and the spatial difference is not very large. Based on the actual situation in the study area, the natural breakpoint method was used to classify the mean annual temperature sensitivity into five levels (Table 2), and the results and statistics are presented in Figure 3a and Table 4. It can be seen that the sensitivity is higher in the central and eastern parts of the Tumen River Basin, and it decreases in the west, north, and south. In general, the slightly sensitive, moderately sensitive, and highly sensitive areas are more or less evenly distributed, with a lower proportion of insensitive and extremely sensitive areas.
2. Annual precipitation. The result of the annual precipitation sensitivity classification of the Tumen River Basin is shown in Figure 3b. The central region of the basin is extremely sensitive, while the sensitivity of other regions gradually decreases from the center to the periphery. The area proportion of highly sensitive areas is the highest,  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Target Layer** & **Criterion Layer** & **Weights** & **Evaluation Indicator Layer** & **Weights** & **Weight Sort** \\ \hline \multirow{6}{*}{Ecological sensitivity} & \multirow{6}{*}{Natural environment} & \multirow{6}{*}{0.3119} & Mean annual temperature & 0.0601 & 7 \\  & & & Annual precipitation & 0.0841 & 5 \\  & & & Elevation & 0.1300 & 3 \\  & & & Distance to water & 0.0377 & 9 \\  & & & Type of land use & 0.2643 & 1 \\  & & & Distance to construction land & 0.1458 & 2 \\  & & & Distance to road & 0.0803 & 6 \\  & & & Topographic relief & 0.0513 & 8 \\  & & & Rainfall erosivity & 0.0238 & 11 \\  & & & Soil texture & 0.0337 & 10 \\  & & & Vegetation coverage & 0.0888 & 4 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Weigh of ecological sensitivity evaluation factors.  
followed by extremely sensitive areas, and the area proportion of moderately sensitive areas, slightly sensitive areas, and insensitive areas gradually decreases.
3. Elevation. The Tumen River Basin is located in the Changbai Mountain Range, with elevations ranging from 8 m to 1689 m. The elevation varies greatly and the topography is undulating. As shown in Figure 3c, the sensitivity is higher in the higher elevation areas in the south and north, and lower in the central and eastern river valley plains. The area of slightly sensitive areas and moderately sensitive areas account for a relatively large proportion of the study area, while insensitive areas and highly sensitive areas account for a relatively small proportion, and only 1.66% of region are extremely sensitive areas.
4. Distance to water. Water bodies, such as rivers, lakes, and reservoirs, play an important role in maintaining the regional ecological balance. In this study, the ecological sensitivity levels were classified according to the distance from water (Table 2), and the results are shown in Figure 3d. The ecological sensitivity in the study area is closely related to the distribution of the Tumen River main stream, tributaries at all levels, lakes, reservoirs, and other water bodies. The proportion of the area of insensitive and slightly sensitive areas is relatively large, totaling 60.67%. The proportion of moderately sensitive and highly sensitive areas is relatively low, and the area of extremely sensitive areas is 1942.47 km\({}^{2}\), which is the smallest proportion of the area.  
Figure 3: Distribution of ecological sensitivity of the natural environment.