Acta Scientiarum Polonorum

The study aimed at the determination of the tensile strength of the roots of common birch, European
hornbeam and Scots pine and at the estimation of values of Weibull functions parameters (ω, λ) describing
the variability of this characteristic depending on the species and the size of the root diameters. Tensile
strength tests were carried out on the root samples that were placed in water at least one day prior to the
test, in order to obtain their maximum saturation. The results of the tensile strength tests and Weibull function
parameters values were used for the calculation of root cohesion using numerical model (fiber bundle
model).
The test results revealed that the roots of the European hornbeam have statistically significantly higher tensile
strength than the roots of the common birch and Scots pine. The results of the analysis showed that the
values of Weibull parameters are generally small. The obtained values of the ω parameter indicate a high
variability of the tensile strength characteristics of the roots of the examined plant species. It has also been
shown that Weibull’s method of selection of parameters can have a significant effect on the results of the
root cohesion calculations. Moreover, the root cohesion values obtained by the fiber bundle model using
the Weibull function were 15–55% smaller than those obtained using the classic Wu-Waldron model.