Coarse grain models and functional groups: Two examples of perfect aggregation in modelling non-disturbed tropical rainforests.
Franc, Alain*,1, Picard, Nicolas1, 1 Département Ecologie des Forêts, Prairies et Milieux Aquatiques, CDA & UMR Biodiversité, Pierroton
ABSTRACT- The structure of a tropical rainforest can be described and its dynamic modelled at different scales, more often from trees to stands and regions. One objective of modelling is to have fluent translations of models from one scale to another. We present here two applications of a technique, perfect aggregation, which enables to test whether two models on the same system but at different scales are compatible or not. We show, on a specific case study on permanent plots in French Guiana, that distribution based models can be a very precise approximation of individual based models. We show how this approximation is related to mean field approximation, or moment closure. Trees can be described not only by points in space and time, but also by parameters attached to some of their life traits. Many works have been performed on how to summarize the pattern of life traits into fewer categories of functional groups. We show, on a second case study, how the translation from a list of life traits on a set of trees into categorization into a limited number of functional groups can be read as a perfect aggregation also, in the parameter space. We explore how this modelling approach can be a complement to more established methods relying on data analysis, or promising methods relying on measurements of functional traits, like water use efficiency.
Key words: tropical forest
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