Variability in root biomechanics of Chrysopogon zizanioides for soil eco-engineering solutions

Abstract

AimsWe investigated and compared the variability in biomechanical properties of Chrysopogon zizanioides L. (vetiver grass), including tensile strength, Young's modulus, and breakage strain, which have direct implication to root reinforcement to slope. MethodsWe tested the effects of growth condition (pots versus field), root water content (hydrated versus oven dried), and loading speed (16 mm/min versus 200 mm/min) on the biomechanical properties of vetiver roots (n = 344) via a series of uniaxial tensile tests. We also measured the root biomechanical traits such as diameter, density, degree of saturation, and relative root dry weight. ResultsAlthough the strength and modulus followed a negative power law relationship with root diameter (R2 up to 0.69), the strain–diameter relationship was linear (R2 = 0.20). Growth condition and loading speed did not have significant effects on the root biomechanical properties, whereas root water content showed significant effects on these properties, particularly in fine roots (<0.9 mm). Dried roots had higher strength and modulus but smaller strain than hydrated roots. ConclusionA major source of the variability in strength, modulus, and strain of vetiver roots was root water content, which occurred primarily in fine roots (<0.9 mm). Considering slope stability, testing hydrated roots would give a lower estimate of strength than the case of dried roots, but it might overestimate root ductility and underestimate the time-of-slope failure.