The effect of pollarding on tensile strength of Persian oak (Case Study: Dinarkooh, Ilam)

Previous studies have shown that vegetation enhances the soil shear strength and the stability of slopes through soil reinforcing. The amount of reinforcement mainly depends on the density and tensile strength of the root. The objective of this study was to assess the impact of pollarding on tensile strength of Quercus persica roots. For this purpose, five treatment and five control tree samples were randomly selected. Some root specimens for each tree were collected and tensile strength was measured by a standard Instron. 150 successful tensile tests were conducted on roots withdiameter ranging from 0.9 to 5.5 mm, force range of 3-374.5 N and tensile strength range of 1.22-217.80 MPa. The relationship between root diameter and force was following a positive power one but the power relationship between the root diameter and tensile strength was not statistically significant. The results of Wald Chi square test showed there was no significant difference between the tensile strength of treatment and control sample trees, although the root diameter (as covariate) had a significant effect on tensile strength. It can be concluded that no significant differences may relate to short history of pollarding (3 years) in the study area, and therefore it is suggested to assess the stands with longer history of pollarding.