Effects of root dehydration on biomechanical properties of woody roots of Ulex europaeus

D Boldrin,Anthony K Leung,A G Bengough

doi:10.1007/s11104-018-3766-7

Abstract

AimsEffects of root water status on root tensile strength and Young’s modulus were studied in relation to root reinforcement of slopes.MethodsBiomechanical properties of woody roots, Ulex europaeus, were tested during progressive dehydration and after thirty-day moisture equilibration in soil with contrasting water contents. Root diameter, water content and water loss were recorded and root water potential versus water content relation was investigated. Tensile stresses induced by root contraction upon dehydration were measured.ResultsRoot tensile strength and Young’s modulus increased abruptly when root water content dropped below 0.5 g g−1. The strength increase was due to root radial and axial contraction induced by root water potential drop. Diameter decrease and strength gain were the largest for thin roots because of the relatively larger evaporative surface per volume of thin roots. Largely negative water potentials in dry soil induced root drying, affecting root biomechanical properties.ConclusionRoot water status is a factor that can cause (inappropriately) high strength values and the large variability reported in literature for thin roots. Therefore, all root diameter classes should have consistent moisture for fair comparison. Testing fully hydrated roots should be the routine protocol, given that slope instability occurs after heavy rainfall.

Highlights

Several above- and below-ground plant traits have been shown to affect slope stability by root mechanical and hydrologic reinforcement (e.g. root biomechanical properties, root length density, root biomass (Boldrin et al 2017a; De Baets et al 2009; Ghestem et al 2014b; Loades et al 2010; Ng et al 2016 ; Saifuddin and Osman 2014; Stokes et al 2009; Yildiz et al 2018))
The objective of this study is to investigate the effects of root drying on root biomechanical properties, aiming to answer the following research questions: (i) Do root tensile strength and Young’s modulus increase with root drying? (ii): Are variations of root biomechanical properties upon drying associated with (a) calculation effects due to diameter change or (b) changes in material properties? (iii) Do soil water content and soil water potential affect the biomechanical properties of roots permeating the soil? The experiments reported in this study tested these hypotheses using Ulex europaeus roots sampled from mature plants
The relation between diameter and strength started to change after 2 h (Fig. 2d), when a tensile strength value up to 48.0 MPa was recorded in a thin root (0.50 mm)

Summary

Introduction

Several above- and below-ground plant traits have been shown to affect slope stability by root mechanical and hydrologic reinforcement (e.g. root biomechanical properties, root length density, root biomass (Boldrin et al 2017a; De Baets et al 2009; Ghestem et al 2014b; Loades et al 2010; Ng et al 2016 ; Saifuddin and Osman 2014; Stokes et al 2009; Yildiz et al 2018)) Root biomechanical properties such as tensile strength and Young’s modulus are the most studied traits in soil bio- and eco-engineering, and they are commonly used to quantify plant effects on slope stability (Bischetti et al 2005; Fan and Su 2008; Mickovski et al 2009; Loades et al 2013; Mao et al 2012; Mattia et al 2005; Schwarz et al 2010; Stokes et al 2008; Wu et al 1979). There is yet to be a commonly accepted explanation for the

Methods

Results

Discussion

Conclusion