Root Traits and Mechanical Properties of Three Shrubland Species: Implications for Bioengineered Slope Stability

Abstract

This study aimed to evaluate the ability of three shrubland species to consolidate slopes using root morphological traits and mechanical properties. The results showed that root tensile force increased and root tensile strength decreased with root diameter (from 0.3 to 5.5 mm) among all study species. Under the same level of root diameter, root tensile force and root tensile strength were highest for Amorpha fruticosa Linn. (AFL), followed by Swida alba Opiz (SAO) and lowest for Lespedeza bicolor Turcz (LBT). The mean branching ratio, root angle, stele to root diameter ratio, specific root length, individual length and surface area, and mean diameter of fine roots in different slopes were higher for AFL and SAO than for LBT, especially for high root orders (the third to fifth root orders). Furthermore, total hyphae length, total hyphae surface area, total hyphae volume, hyphae mean diameter, total glomalin-related soil proteins (GRSP), and easily extractable GRSP in different slopes also were highest for AFL, followed by SAO and lowest for LBT. However, root and mycelium traits had a positive effect on soil cohesion. These results suggested that root traits and mechanical properties of AFL and its impact on soil properties would enable more effective to consolidate slopes than SAO and LBT, revealing that planting AFL might be a better way for enhancing bioengineered slope stability in this study region.