The Effect of Root Native Tree Species on Soil Shear Strength on Hillslopes of Sierra Madre Oriental, Mexico

Abstract

Background: The presence of vegetation reduces soil erosion and shallow slope failure both by reinforcing soil shear resistance and influencing the geo-mechanic conditions of soil. For this reason, vegetation strategies in areas vulnerable to erosion are considered to be an effective control measure for soil erosion. Method: The tree species used in this research are widespread in the slopes of Chipinque mountain of Sierra Madre Oriental and belong to four native species: Cercis canadensis, Celtis laevigata, Quercus rysophylla and Ligustrum lucidum. In order to investigate the mechanical characteristics of roots, single roots specimens were sampled and tested for tensile strength. The tests were conducted with the Universal Testing Machine Shimadzu type SLFL-100KN to evaluate the influence of root shear strength on the soil using the Wu Model (Wu et al., 1979) as well as to analyze root cohesion and Root Area Ratio (RAR). The latter was calculated by taking both direct (field) and indirect measurements on image processing.Results: The results show that C. laevigata roots have the strongest tensile strenght, followed by Q. rysophylla > C. Canadensis > L. lucidum. RAR ranges from C. laevigata (0.0587%) > C. Canadensis (0.0585%) >L. lucidum (0.0504%) > Q. rysophylla (0.0441%). L. lucidum provides the less increase soil shear strength through root cohesion (16.12 kN/m2) > C. canadensis (53.70 kN/m2) > Q. rysophylla (89.07 kN/m2) to C. laevigata (97.41 kN/m2)