# Influence of Vegetation Filter Strip on Slope Runoff, Sediment Yield and Nutrient Loss
## 4 Discussion  
### Relationships between Erosion Indexes and Influencing Factors  
Multivariate regressions were performed to determine the relationship between erosion indexes (sediment and runoff yield, TN and TP loss) and the influencing factors of rainfall intensity, slope gradient and vegetation (Table 3). Except for TP loss in sediment, the coefficient of determination \(R^{2}\) was generally relatively high, which can explain more than 60% of the variability, demonstrating that multiple regression analysis can explain and predict the variation of each erosion index to a large extent. The results of regression coefficient and multivariate analysis of variance showed that rainfall intensity, slope and vegetation had significant effects on sediment yield, runoff yield, TP loss in runoff and TN loss in sediment (\(p<0.05\)), which has been confirmed in previous studies [45]. [PERSON] [46] believed that rainfall intensity and slope were positively correlated with erosion. However, in terms of TN loss in runoff and sediment, erosion was negatively correlated with rainfall intensity and slope in this study, respectively. Since vegetation, which is antagonistic to rainfall intensity and slope, was dominant in affecting TN loss. The modes of soil nutrient loss include runoff and eroded sediment. The former is mainly soluble nutrients, while the latter is mostly mineralizable nutrients [47]. The regression results showed that the slope gradient had no significant effect on TN loss in runoff, which indirectly indicated that TN loss was mainly carried by sediments. The coefficients of dummy variable \(V_{0}\) in the regression equation were all positive, which had a negative impact on erosion, indicating that the erosion of the bare surface increased compared with the vegetation coverage. In addition, the regression coefficient of dummy variable \(V_{1}\) in the linear equation between TN loss in runoff and influencing factors was relatively large, indicating that vegetation setting modes had a certain degree of influence on it. Therefore, \begin{table}
\begin{tabular}{c c c c c c} \hline
**Erosion Index** & \multicolumn{3}{c}{**Regression Equation**} & \begin{tabular}{c} **Determination** \\ **Coefficient R\({}^{2}\)** \\ \end{tabular} & \
\begin{tabular}{c} **\(p\) Value** \\ \end{tabular} &
\begin{tabular}{c} **N** \\ \end{tabular} \\ \hline Sediment (g) & \(Y=-288.547+4.478\times R+5.229\times S+86.496\times V_{0}+2.516\times V_{1}\) & 0.617 & 0.000 & 54 \\ Runoff (L) & \(Y=-13.743+0.387\times R+0.348\times S+7.422\times V_{0}-0.035\times V_{1}\) & 0.850 & 0.000 & 54 \\ TP in runoff (mg/L) & \(Y=-0.172+0.008\times R+0.006\times S+0.0223\times V_{0}+0.0044\times V_{1}\) & 0.839 & 0.000 & 54 \\ TP in sediment (g/kg) & \(Y=0.510+0.004\times S+0.118\times V_{0}+0.020\times V_{1}\) & 0.434 & 0.000 & 54 \\ TN in runoff (mg/L) & \(Y=14.769-0.028\times R+0.011\times S+3.454\times V_{0}+0.812\times V_{1}\) & 0.697 & 0.000 & 54 \\ TN in sediment (g/kg) & \(Y=0.675+0.005\times R-0.012\times S+0.413\times V_{0}-0.014\times V_{1}\) & 0.714 & 0.000 & 54 \\ \hline \end{tabular} Note: \(Y\) stands for the corresponding erosion index; \(R\) stands for rainfall and \(S\) stands for slope; \(V_{0}\) and \(V_{1}\) stand for the two dummy variables.  
\end{table} 
Table 3: Relationship between erosion indexes and rainfall intensity, slope and vegetation coverage type. it is necessary to continue to analyze the relationship between erosion and rainfall intensity and slope under different vegetation cover types. Binary regressions of erosion indexes and influencing factors including rainfall intensity and slope were performed in different vegetation coverage type (Table 4). The coefficients of determination \(R^{2}\) of linear equations were generally quite high, indicating a better regression effect. The study found that there were significant differences in the runoff and sediment yield, TN and TP loss in runoff and sediment between vegetation-covered slopes and bare land slopes (\(p<0.05\)).