# Application of Compound Terrain Factor LSW in Vegetation Cover Evaluation
## 4 Results and Discussion  
### Multi-Factor Analysis of Vegetation Cover  
Taking the DEM of the study area as the foundation, the topographic factors LSW, LS, TWI, and aspect were calculated; subsequently, the reclassification work was carried out. Among them, the slope aspect starts from a clockwise direction and is divided into nine categories according to 45\({}^{\circ}\) as the grading interval, and then considering the flat land situation where the slope aspect does not exist. For LSW, LS, and TWI, the natural breaks classification was applied for reclassification. The method adopts a similar idea to clustering, taking the maximum similarity within each group and the maximum difference between different groups as the starting point, while balancing the need for the range and number of elements in various groups to be as close as possible so as to satisfy the reasonable division of each level. Ultimately, LSW, LS, and TWI were all classified into five categories. After the classification was completed, the results of calculating the CF values of each class for each factor are shown in Table 1.  
Synthesizing the data in Table 1, the LSW factor of the experimental group was analyzed versus the factor of the control group, as follows. 1. LS and LSW: LS factor as a component of the USLE is directly linked to the hydraulic erosion suffered by the soil, and is more intuitively expressed as a linear correlation; in other words, the larger the LS factor is, the more serious the soil erosion is within the region. Based on the above analysis, the five gradations of LS factors also exhibit a clear regularity. With the division of grade I-V, the CF value shows a tendency to shrink from near zero value to negative value amplification, which is related to the properties of LS itself. In particular, The CF value of grade IV and V in LS reaches \(-0.5\), which had a significant effect on the vegetation growth and development. It was shown that as the LSW factor increased from grade I to V, the corresponding CF values showed a clear pattern of changing from negative to positive values, which was considerably different from the pattern of the LS factor. Compared with the LS factor, the LSW factor not only ensures the reasonable preservation of the fusion information, but also supplements the slope width information to help it express the ground information more thoroughly, which is also empirically supported by the information entropy test [28]. The rules of LSW gradation corresponding to CF in Table 1 are notable, which means the LSW value can effectively determine whether a particular area of land is suitable for vegetation growth. 2. TWI: TWI is a measure of soil water content and potential magnitude of runoff occurrence in a certain region. If the TWI is higher in a region, the corresponding saturated zone has a greater potential for development [69]. From the principle of vegetation growth, if the soil is highly saturated with water, it is easy to produce surface runoff. Once the soil remains saturated with water for a long time, the water balance in the vegetation cells is disrupted. This is not conducive to the absorption of plant nutrients such as Ca, K, Mg [74], thus affecting the vegetation growth and development. According to Table 1, the CF value corresponding to TWI decreases gradually as the grade increases, indicating that excessive water saturation in the soil is instead detrimental to the vegetation cover, which is consistent with the vegetation growth law. 3. Aspect: As seen in Table 1, the slope aspect of the flat land shows a significant negative effect with vegetation cover. Due to the absence of the slope aspect means that the ground is not deflected in either direction, the vegetation is more likely to be dominated by other factors in such cases. The study period is in the spring to summer transition stage, dominated by the temperate atmospheric mass. However, the study areas with SW, W, and NW aspects showed a positive correlation.