Mechanical properties of “flexure wood”: compressive stresses in living trees improve the mechanical resilience of wood and its resistance to damage

Abstract

& Key message Mechanical acclimation of young poplars (Populus tremula × Populus alba, INRA 717-1B4) submitted to periodic stem bending is mainly driven by strains. Flexure and exhibit higher mechanical resilience and lower mechanical damage. & Context It is well known that thigmomorphogenesis modulates tree growth and the anatomical structure of However, nothing is known about the mechanical behaviour of the tissues of fresh formed under mechanical stimulation. & Aims We investigated the elastic and plastic properties of the fresh of young poplar trees (Populus tremula × Populus alba, INRA 717-1B4) submitted to periodic controlled stem bending that mimics the mechanical effect of wind. & Methods For a set of trees, we applied symmetrical bending treatments, which led to the formation of flexure wood. For another set of trees, asymmetrical bending treatments, including compression (or tension) only, were applied and generated specific formation: compressive wood and tensile wood. We investigated the elastic and plastic properties of these woods at the stem and at the local tissue levels. & Results The results revealed that fresh formed under treatments is more resistant to damage (damage reduced by 44%) and a higher mechanical resilience (+ 33%), suggesting that this tissue is able to withstand higher mechanical strains than normal wood. This improvement could explain the higher mechanical strength of the stem to bending (+ 42%). & Conclusion When trees experience repetitive mechanical stimulations, they adjust the plastic plastic behaviour of their in a way that improves the mechanical safety. This demonstrates the adaptive benefit of the mechanical acclimation of trees.