Exploring the variability in elastic properties of roots in Alpine tree species

Quantifying the soil reinforcement provided by roots is essential for assessing the contribution of forests to reducing shallow landslide susceptibility. Many soil-root models were developed in the literature: from standard single root model to fibre bundle model. The input parameters of all models are the geometry of roots (diameter and length) and the biomechanical properties (maximum tensile force and elastic modulus). This study aims to investigate the elastic properties estimated by the stress-strain curves measured during tensile tests. A standard procedure detected two different moduli of elasticity: one due to the root tortuosity, and the other due to the woody fibres of roots. Based on a large dataset of tensile tests on different Alpine tree species, the relationships between elastic modulus and root diameter was estimated for each series. Further, the interspecific and intraspecific variability in such relationships was investigated by a statistical analysis. The results showed more intraspecific differences in the elastic modulus vs. root diameter relationships compared to the interspecific ones. This outcome could be an important criterion of discrimination to explain the variability of the elastic properties and to provide representative biomechanical properties for specific environmental conditions.