Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: Preliminary measurement and simulation of the spatial distribution of the Morphogenetically Active Radiation (MAR) within an isolated tree canopy. | 497 Ann. For. Sci. 57 2000 497-511 INRA EDP Sciences Original article Preliminary measurement and simulation of the spatial distribution of the Morphogenetically Active Radiation MAR within an isolated tree canopy Didier Combes 1-1 - . Hervé Sinoquetb and Claude Varlet-Granchera a Station d Ecophysiologie des Plantes Fourragères INRA 86600 Lusignan France bUMR PIAF INRA - Université Blaise Pascal 63039 Clermont-Ferrand Cedex 1 France Received 19 February 1999 accepted 2 September 1999 Abstract - Light quality . the solar radiation spectrum is involved in developmental processes of plants including trees. Characterisation of morphogenetically active radiation MAR within a canopy is necessary in order to take into account photoregulation of the architecture in tree simulation models. This study was a first attempt at describing and simulating the spatial distribution of light quality within a walnut tree crown Juglans regia L. using both spectral measurements and a radiation transfer model based on the turbid medium analogy. Both measurements and simulation were qualitatively in agreement. They showed large differences in light quality between shaded and sunlit areas. The range of measured and simulated values was in agreement with values reported in the literature. The quantitative comparison between measurements and model outputs showed large discrepancies. The latter were attributed to the rough treatment of scattering in the model the small amount of punctual measurements made in the tree and the high sensitivity of input parameters such as the diffuse to incident radiation ratio and canopy structure description. Nevertheless the model was mostly able to describe the range of MAR values phytochrome equilibrium c blue transmittance found in the tree canopy. radiation transfer phytochrome cryptochrome photomorphogenesis Résumé - Simulation de la distribution spatiale du Rayonnement Morphogénétiquement Actif au sein de la couronne d un arbre isolé. La qualité de
