A model to simulate the gravitropic response and internal stresses in trees, considering the progressive maturation of wood

Trees-Struct. Funct. ISI Document Delivery No.: AM5EH Times Cited: 0 Cited Reference Count: 21 Pot, Guillaume Coutand, Catherine Toussaint, Evelyne Le Cam, Jean-Benoit Saudreau, Marc Auvergne Regional Council; European Regional Development Fund This work was supported by a grant from the Auvergne Regional Council and the European Regional Development Fund. Springer New yorkInternational audienceThe developed model of gravitropism takes non-instantaneous maturation of wood into account which enabled to correctly simulate different gravitropic phases and realistic internal stress profiles. A new biomechanical model of tree movement in relation to gravity (gravitropism) is proposed in this study. The modelling of the progressive maturation of wood cells is taken into account, as well as spatio-temporal variations in maturation strains (MS) and mechanical properties. MS were identified using an inverse method that allows the model to fit the gravitropic reaction observed experimentally. For this purpose, the curvature during righting movement, the geometry and the mass distribution of a two-year-old poplar tree was measured. The identified MS are higher than expected, which shows the underestimation of MS by usual measurements. By using the same mechanical parameters and MS as an input, the model gives satisfying results in terms of shape modelling for different trees up to 32 days after tree tilting. The model is able to simulate the latency phase observed in the tree righting movement, and the internal stress profile in the trunk is realistic (low compressive value in the central part of the trunk and zero stress in newly formed cells). The next development of the model will aim to simulate the end of the gravitropic phase in relation with the regulation of MS by the tree

A double-digitising method for building 3D virtual trees with non-planar leaves: application to the morphology and light-capture properties of young beech trees (Fagus sylvatica)

We developed a double-digitising method combining a hand-held electromagnetic digitizer and a non-contact 3D laser scanner. The former was used to record the positions of all leaves in a tree and the orientation angles of their lamina. The latter served to obtain the morphology of the leaves sampled in the tree. As the scanner outputs a cloud of points, software was developed to reconstruct non-planar (NP) leaves composed of triangles, and to compute numerical shape parameters: midrib curvature, torsion and transversal curvature of the lamina. The combination of both methods allowed construction of 3D virtual trees with NP leaves. The method was applied to young beech trees (Fagus sylvatica L.) from different sunlight environments (from 1 to 100% incident light) in a forest in central France. Leaf morphology responded to light availability, with a more bent shape in well-lit leaves. Light interception at the leaf scale by NP leaves decreased from 4 to 10% for shaded and sunlit leaves compared with planar leaves. At the tree scale, light interception by trees made of NP leaves decreased by 1 to 3% for 100% to 1% light, respectively

Exploring carbon allocation with a multi-scale model: the case of apple

UMR AGAP - équipe AFEF - Architecture et fonctionnement des espèces fruitièresUnderstanding the allocation of carbohydrates among organs is necessary to predict plant growth in relation to climatic conditions and agronomic practices. Despite the large number of studies on the subject of carbon allocation, no clear consensus exists on (i) the most appropriate topological scale (organ, metamer, compartment...) to represent this process on complex plant structures, and (ii) the importance of distances between organs in carbon transport. In this study, we implemented a generic source-sink based carbon allocation model, following the equation of the SIMWAL model, that takes into account the distances between sources and sinks, the sink strength and the availability of carbohydrates from photosynthesis. Our model makes use of multi-scale tree graph (MTG) to represent geometry and topology of a tree structure at different scales. Starting from the description of a plant at a given scale (e.g. metamer and growing unit scales), we defined additional grouping criteria (fruiting branches and main axis) that were used to represent the plant structure, and the process of carbon allocation at different spatial resolutions. Generic functions to determine the biomass and carbon demand of the individual organs described in an MTG were implemented and calibrated for apple trees (Fuji variety) by means of age and organ type dependent allometric equations and maximum potential Relative Growth Rate curves (RGR) obtained in a field experiment. Photosynthesis for individual leaves of the input MTG was estimated by means of a radiative model (RATP). The model was then applied to architectural mock-ups in the MTG format produced by the MappleT model, representing trees with high and low fruit loads. Simulations on simplified plant structures qualitatively showed the influence of the scale of representation and of the distance parameter on the predicted carbon allocation. In order to test assumptions regarding the effect of distance, the source-sink behavior and the suitability of the alternative scales of representation for predicting carbon allocation, the variability and spatial distribution of the simulated RGR were compared to field observations. Finally, a benchmarking was performed to compare the computational efficiency of the model when running at different scales. The presented multiscale model provides a framework to re-interpret the plant topology in order to test the influence of some assumptions at the basis of the carbon allocation process, such as branch autonomy or the effect of distance. It is also a mean to investigate the trade-offs between the detail at which a plant is described, and the accuracy and computational efficiency in predicting carbon allocation. The present work was developed on the OpenAlea platform, and will provide existing Functional Structural Plant Models with a new generic model to simulate carbon allocation in plants

Les intérêts de l’arbre en milieu urbain face au changement climatique

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ANR COOLTREES. Le rafraichissement des villes par les arbres - Quantification et modélisation

National audienceLes forêts sont au cœur de nombreux enjeux sociétaux et environnementaux qui soulèvent des questions de recherche variées. Afin de présenter les avancées scientifiques de projets soutenus sur cette thématique, et favoriser les échanges entre chercheurs, pouvoirs publics, entreprises et acteurs de la société, l’ANR organise un colloque les 30 et 31 mars 2021. Compte tenu des incertitudes sur la tenue d’un tel événement en présentiel, le colloque se déroulera uniquement en ligne, avec un programme légèrement modifié

COOLTREES. Le rafraîchissement des villes par les arbres – Quantification et modélisation pour le développement de villes durables

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Arbres et ville : l'enjeu de la température

INRA - L'E-TRAVERSE Communiqué de presse https://intranet.ara.inra.fr/Vie-collective/Newsletter/e-Traverse/3e-trimestre-2019/195/Vie-scientifique-et-technique/Arbres-et-ville-l-enjeu-de-la-temperatureParmi les stratégies d'adaptation des villes aux changements climatiques et notamment aux événements de chaleur extrême, la réintroduction de la végétation en ville est une solution intéressante. La végétation, par sa transpiration et son ombrage, a en effet un impact significatif sur le bilan énergétique de l'atmosphère urbaine. Un programme de recherches démarré en 2017, "CoolTrees"(*), vise à améliorer la modélisation de cet impact, en lien avec la topographie urbaine

Les intérêts de l'arbre en milieu urbain face au changement climatique. Programme Cooltrees rafaichissement urbain par les arbres

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