Rôle de l'architecture dans l'interception lumineuse des couronnes de Tectona grandis et Acacia mangium. Utilisation pour la simulation des bilans radiatifs dans les systèmes agroforestiers.

摘要

In a two-stata agroforestry system, transmitted photosynthetically active radiation distribution under the tree canopies is a limiting factor for the establishment and growth of intercrops. Light distribution changes according tyo season and tree canopy development. The light available for the intercrops depends on the quantity of light intercepted by the tree canopies and consequently on the architecture ot the tree species considered. The aim of this work is to define for two species, Acacia mangium Wild. adn Tectona grandis L. , the role of the tree architecture in (i) light capture modalities by the tree canopy and by leaves and (ii) intra- and interspecific light distribution under the tree canopy accordingto tree age. From the dynamic analysis of growth and branching processes for these two-species, a leaf sampling enables to determine leaf display, leaf geometrical pattern and morphological, anatomical, optical properties and biochemical leaf characteristics within the tree crown. Through growth simulationof these two species, based on growth and brancing mathematical law, 3D virtual trees were constructed to simulate agroforestry plots radiative balance. the results show high intra- and interspecific variations in leaf display and leaf characteristics within the tree crowns and in light distribution under treecanopies. The strategies of light capture efficienty adopted by the two-species are discussed