Evaluation of the root system resistance against failure of urban trees using principal component analysis

•Two methods how to calculate anchorage root stiffness were discussed.•Different root stiffness between intact and damaged group of trees was found.•The PCA method allows to see the similarity of surveyed trees with trees of known state.

The resistance against failure is an important topic of recent arboricultural research. Trees in urban environments are particularly of interest because of the damage they can cause. Root system anchorage stiffness is the variable that allows the resistance of the root–soil plate against failure to be quantified repetitively and non-destructively. This study uses principal component analysis (PCA) to evaluate tree mechanical state, when the input parameters are the load parameters and suitable root–soil plate stiffness parameter. The PCA method allows the similarity of surveyed trees within a control group with known mechanical state to be identified. Thus, the mechanical stability of surveyed trees can be evaluated.