Root System Traits of Three Shrublands Species: Implications for the Structural Stability of the Ecological Slope

To improve the structural stability of the ecological slope planting shrubs on both sides of the road is a common phenomenon in highway engineering. The shrub for improving the structural stability plays an important role in the anti-scouring resistance and erosion resistance of the road slope. Although previous studies have focused on the relevant content, the reinforcement ability of different shrubs is rarely quantitatively compared under the same road conditions. Through the field investigation, we found three common slope structural stability protection shrubs. The three shrubs are Amorpha fruticosa Linn. (AFL), Syringa oblata Lindl. (SOL) and Forsythio mandshurica Uyeki. (FMU). The results shown that the single root withdrawal force of three shrubs was proportional to the size of diameter (from 0.6-6 mm). Under the same root diameter conditions, AFL also had the highest single withdrawal force at the slope of 60°. Morover, the morphology traits of the fine root (<1mm) and soil properties affecting soil reinforcement were considered in this study. The mean specific root length, individual length and surface area, and mean diameter of fine roots in different slopes were higher for AFL and SOL than for FMU, especially for high root orders (the third to fifth root orders). These results suggested that the root system traits of AFL and their impact on soil properties would enable more effective consolidated slopes structure than SOL and FMU, revealing that planting AFL might be a better way for enhancing ecological slope structure stability.