EMILION, a tree functional-structural model: Presentation and first application to the analysis of branch carbon balance

This paper summarises the main characteristics of a new functional-structur al. ecophysiological model EMILION elaborated for pine species. It is based on the integration of the functioning of the tree aerial organs, shoots, b uds and cones. It is founded on the modelling of carbon- and water-related processes at the organ level, and on the links that exist between the organ s. The main processes described by EMILION are light distribution and inter ception, photosynthesis, respiration, stomatal conductance, transpiration, water transfer, phenology, and intra-annual growth. It uses an object-orien ted approach. It has been parameterised and applied to adult Maritime pine (Pinus pinaster Ait.). The model simulates the distribution in the tree of carbon and water fluxes at a short time step. The principal inputs are stan d and tree structure, and meteorological data. EMILION allows one to study the interaction of processes at the organ and tree level. An example applic ation is presented, in which EMILION was used to simulate the carbon budget of existing branches, according to their age and location within the crown . This study was used to test one hypothesis of branch death, that death is a consequence of an imbalance between branch assimilate production and use . Our results show that the old branches of Finns pinaster are autonomous f or the carbon, but the ability of these branches to supply assimilates to r est of the tree appears very low. We conclude that this small carbon availa bility in the oldest branches is a cause of their limited development.