Résumé
The project sets out to understand how the diversity of wood structures and properties allows woody plants, including different life forms, to develop a diversity of growth strategies during regeneration stages (seedlings, saplings and juveniles) in a tropical rainforest understorey characterized by a strong competition for light and a huge diversity of functional types of tropical woody plants. Expected results concern i) the definition of biophysical traits related to these strategies, with improved theoretical and experimental methods, ii) some answers to ecological questions about trade offs between hydraulic and mechanical performances in the particular context of tropical rainforests, iii) a set of data on biophysical traits – measured for the needs of the previous questions - included in a more general data-base of tropical tree traits. Traits related to wood hydraulic and mechanical performances will be defined from measurements at different scales (from the whole organism to wood cell wall chemical components) and biophysical models of their functional significance. A large range of unconventional wood properties will be investigated as trade offs at different scales contribute to maintain all the performances at a high level. Then their variations will be studied among the diversity of woody plant species, comparing life forms (self supporting tree, climbers, epiphytes) and trees from different functional groups. Within-species wood variations during ontogeny and with environmental conditions, as well as physiological processes involved in wood adaptations to hydraulic and mechanical constraints, are assumed to play a key role in growth strategies. Therefore, we propose to check these hypotheses; the ecological significance of these factors in natural conditions will be studied, as well as the inter-species variations of physiological processes, including the genetic variations of response and perception to biomechanical constraints, using recent advances in tree genomics.