Growth behaviour of trees and relationship with some descriptors of the environment

In tropical rainforests, trees over 10 cm diameter at breast height (DBH) show a great variability in diameter increments. We first characterise the phenomenon on the Paracou plots and examine its evolution over time and according to silvicultural treatments. Among the many factors which can explain the variability of growth, some can be more or less easily examined with the data available on the site: annual rainfall, botanical identity, size of the trees, topography and soils characteristics, competition for light, water and nutrients. The last effect can be estimated through the use of competition indices, either one- sided or two-sided (showing the competition for light or for all types of resources, respectively). We have tried to gradually incorporate the most influential factors in a model describing individual growth, and have shown that the residuals include tendencies suggesting that explanatory factors still have to be taken into account. In addition to other results, this work led us to build groups of species which can be qualified as homogeneous as far as diameter increment is concerned. The methods to further improve the explanations of growth variability are discussed. (Résumé d'auteur