The effect of season on resistance of Persian oak (Quercus persica) roots (Case study: Tabarok, Bazaft basin)

Plants as bio-materials in addition to having self-renewal capability، cause no adverse effects on the environment. Vegetation in steep areas have an important effect in the process of soil erosion and its control in comparison with bare soil and therefore plays an important role in improving the stability of the slope. The effects of vegetation in slope stability and hydrological processes depend on tensile strength of roots and determining root tensile strength will provide the information required to analyze the role of roots in the soil improvement. The purpose of this study was to investigate the root tensile strength of Persian oak and comparing its values ​​in leaf on and leaf off seasons. To do this، a relatively uniform hill was selected، root samples were randomly collected from 5 oak trees and tensile strength was measured using a standard Instron. 224 successful tensile tests were conducted with root diameter range of 1. 0- 5. 5 mm، tensile force range of 1. 3-411. 3 N and tensile strength range of 0. 93-1217. 39 MPa. The relationship between root diameter and tensile force and strength were positive and negative power law، respectively. The results of Wald test showed that the difference in tensile strength due to season is significant and the mean strength was higher in winter than summer. The covariate (root diameter) was also statistically significant. This phenomenon may be a mechanism of root system adaptation due to the increased soil moisture content and reduction hydrologic effect of vegetation.