Wind acclimation (thigmomorphogenesis) and wind hazards as major drivers of the shaping of trees though evolution
Résumé
Trees architecture of a broad range of species have been repeatedly as self-similar structures in which branch lengths and diameters vary allometrically within the tree architecture, The currently dominant explanation for such allometric laws results from combining hydraulic optimisation of sap transport with maximal span design versus buckling (through a set of model initiated par the WBE model [1] ). The argument that such “design” could have evolved from mechanical constraints set on trees by wind-loads has been disregarded over the last decades [2].. Using a novel approach combining a Structure-Fonction numerical model of tree growth, light competition and wind&trees interactions with a simulation of the competition and Evolution of heterogeneous forests on a virtual island [4] , we show that all the empirical allometric relationship also emerges from a mechanically-based model based that does not include hydraulics. In this model, called MECHATREE, trees compete for light and the photosynthates are allocated to grow seeds, create new branch segments, or reinforce existing ones through a thigmomorphogenetic response to wind-induced strains [2]. Moreover, wind breaks are modelled as the main selective hazard. These results put emphasis on mechanosensitive growth control and wind breaks as major drivers of the natural selection of tree shapes, especially in habitat in which drought is not as challenging as wind-loads.