  Functional-structural models provide detailed representations of tree growth
and their application to forestry seems full of prospects. However, owing to
the complexity of tree architecture, parametric identification of such models
remains a critical issue. We present the GreenLab approach for modelling tree
growth. It simulates tree growth plasticity in response to changes of their
internal level of trophic competition, especially topological development and
cambial growth. The model includes a simplified representation of tree
architecture, based on a species-specific description of branching patterns. We
study whether those simplifications allow enough flexibility to reproduce with
the same set of parameters the growth of two observed understorey beech trees
(Fagus sylvatica L.) of different ages in different environmental conditions.
The parametric identification of the model is global, i.e. all parameters are
estimated simultaneously, potentially providing a better description of
interactions between sub-processes. As a result, the source-sink dynamics
throughout tree development is retrieved. Simulated and measured trees were
compared for their trunk profiles (fresh masses and dimensions of every growth
units, ring diameters at different heights) and compartment masses of their
order 2 branches. Possible improvements of this method by including topological
criteria are discussed.
