# Ecological Suitability Evaluation for Conservation and Development in Bac Kan Province, Vietnam
## 2 Materials and Methods
### Ecological functional resistance assessment
\begin{table}
\begin{tabular}{l c c c c} \hline \hline  & \multicolumn{4}{c}{**Soil Humidity (\%) at the Soil Depth (cm)**} \\ \cline{2-5}
**Vegetation Type** & **0-5** & **20-25** & **40–45** & **60–65** \\ \hline
1. Bare land & 6.83 & 14.21 & 25.57 & 27.32 \\
2. Savanna and bushes & 23.52 & 27.59 & 30.86 & 31.16 \\
3. Rehabilitated forest after slash and burn & 24.75 & 29.06 & 30.24 & 32.55 \\ cultivation with a crown cover of 70–80\% & 4. Three-stories forest with a crown cover of 70–80\% & 29.56 & 32.74 & 34.79 & 33.58 \\
5. One-story forest without ground vegetative with a & 26.21 & 28.19 & 28.61 & 27.42 \\ crown cover of 70–80\% & 33.79 & 35.94 & 35.98 & 34.37 \\
6. Three-stories forest with a crown cover of 70–80\% & 31.98 & 33.59 & 34.12 & 34.21 \\
7. Two-stories forest with a crown cover of 70–80\% & 18.82 & 20.20 & 21.78 & 22.60 \\
9. _Impetata cylindrica_ savanna & 8.16 & 15.22 & 12.83 & 12.98 \\ \hline \hline \end{tabular} Source: [70].  
\end{table} 
Table 4: Vegetation types and soil humidity at different soil depth levels. \begin{table}
\begin{tabular}{l c c c} \hline \hline
**Forest Structural Types** & **Forest Cover (\%)** & **Number of Stories** & **Rainfall Intercepted by the Canopy (\%)** \\ \hline
1. Forest after rational selective logging with & 70–80 & 3 & 11.67 \\ enough rehabilitation time. & 2. Depleted forest & 30–40 & 1 & 5.72 \\
3. Young forest with enough rehabilitation time & 70–80 & 2 & 10.34 \\
4. Young forest after tending by the old way & 70–80 & 1 & 6.91 \\
5. Forest rehabilitated after slash and burn & 70–80 & 2 & 9.51 \\ cultivation & 70–80 & 1 & 8.96 \\
6. Bamboo forest & \multicolumn{2}{c}{Source: [70].} \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The capability of rainfall interception and forest types. calculate the annual rainfall erosivity factor [72; 73; 74]. The process to calculate the R factor is rather complex and requires long-term data collection. In this study, the R factor was estimated based on a local equation that was introduced by [PERSON] [75] using analysis of the rainfall data over 54 years from 253 meteorological stations throughout Vietnam as follows:  
\[\text{R}\ =\ 0.548257\ \ast\ \text{P}\ -\ 59.9, \tag{4}\]  
where P is the annual precipitation (mm). In practice, spatial interpolation of annual precipitation based on the existing datasets from 1958 to 2018 was carried out using the inverse distance weighted (IDW) technique to generate the rainfall distribution layer and the derived result was used as the input data to produce rainfall erosivity using Equation (4) as shown in Figure 3a. Figure 3: Spatial distribution of USLE factor maps: (**a**) rainfall erosivity factor (R), (**b**) soil erodibility factor (K), (**c**) topographic factor (LS), (**d**) cropping management factor (C), and (**e**) supporting practice factor (P). (b) Soil erodibility factor (K). Soil erodibility represents the effect of soil properties and soil profile characteristics on soil loss. Erodibility is a function of soil texture, organic matter content, and permeability [76]. In this study, K values from different soil types in northern highlands of Vietnam [77] and Ba Be Lake basin [78] as a summary in Table 7 were applied to generate the soil erodibility (Figure 3b). (c) Topographic factor (LS). The topographic factor includes slope length (L) and slope steepness (S). The slope has a major effect on soil erosion rate. The higher the slope, the higher the velocity of overland flow, thus increasing the shear stresses on the soil particles. As slope length increases, the overland flow and flow velocity also steadily increase, leading to greater erosion forces applied to the soil surface [76].