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Understanding plant growth dynamics: links between morpho-anatomical structure and phenology

Caraglio Y., Barthélémy D., Edelin C., Nicolini E.A., Heuret P.. 2016. In : Plinio Sist (ed.), Stéphanie Carrière (ed.), Pia Parolin (ed.), Pierre-Michel Forget (ed.). Tropical ecology and society reconciliating conservation and sustainable use of biodiversity. Program and abstracts. Storrs : ATBC, p. 116. Annual Meeting of the Association for Tropical Biology and Conservation (ATBC 2016), 2016-06-19/2016-06-23, Montpellier (France).

The scientific community explores numerous issues surrounding the carbon storage of tropical forest ecosystems, taking allometric or functional approaches. There is growing interest in the relations existing between climate change and fluctuations in the functioning of forests, in the leaf phenology of species, and in the relations existing between phenology and wood. Because the trunk constitutes the main biomass of the tree, growth is essentially view in terms of diameter and in height, in a letter. The morpho anatomical structure of stem axes, bearing the leaves and underlying the spatial occupation of plants, is seldom considered. Understanding how the system of tree axes is deployed (primary growth, acquisition of resources) and grows (secondary growth, support, translocation and storage) remains a challenge in carbon sequestration issues, but also in those related to forest dynamics. The fundamentals of plant architecture can be found in stem morphology (growth processes, branching, etc.) and the natural levels of organization, such as the axis and the phytomer. Some more temporal levels exist (growth unit, module), and others that are more integrating (architectural model, architectural unit), along with reiterated structures. Methods exist for gaining access to this structural information: monitoring to check the temporal aspect of structure formation; retrospective analysis of plant structure. Reconstructing past development of trees, by combining, in an original manner, the phenology of elongation and thickening on the scale of small branched systems up to the whole plant, reveals the relations existing between leafy shoots, flowering, branching and diameter growth. A comparison with climate data reveals the most susceptible structural variables for a given factor. Architecture plasticity is analysed in terms of balances between leaf/axis (exploitation/exploration of space), elongation/thickening (exploration/support) and brings out some architectural traits and strategies of the tree throughout its ontogeny. The architectural approach provides a conceptual framework for sampling and integrating large trees. The spatial phenology of primary and secondary growth makes it possible to address the rules of prioritization in response to constraints. This dual approach will involve taking another look at biomass and forest ecology matters (colonization of the environment, invasive plants, reforestation). (Texte intégral)

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