Influence of soil in oak root system on its response to bending

Tree root system belongs to a key factor of the tree stability because it provides the anchorage point to the ground/soil, beside its physiological purpose. Therefore, to assess the tree stability with a certainty, it is needed to have information about tree root-plate, ie. to know roots health state, its geometrical distribution in a space with respect to a tree and surrounding objects, to know properties of the ground (soil) and to know material properties of roots. This work assessed 10 oak trees in terms of their reaction to bending induced by a standard pulling test accompanied with optical technique based on digital image correlation to obtain displacement at various locations of tree. Trees were tested in both intact state and with soil removed from the surface of the root plate. Results showed that performed soil removal did not have statistically significant effect on apparent tree stiffness. The same conclusions were found based on data provided by both inclinometers and digital camera.