Parametric identification of a functional-structural tree growth model and application to beech trees (Fagus sylvatica)

International audienceFunctional-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

A new integrative assessment indicator for damage caused by major pests and diseases in the vineyard

An original and integrative evaluation indicator has been developed to quantify the cumulated damage from major pests and diseases affecting grape bunches: downy mildew, powdery mildew, gray mould and tortricid moths. It made it possible to estimate the associated crop losses and to relate them to the plant protection strategy in different modes of production (organic farming, in-transition, conventional). Thus, overall plant losses were higher in 2012 than in 2011. The in-transition growers’ strategy, with reduced copper doses but increased numbers of sprays, led to a 20% increase in average severity on bunches (essentially due to Downy mildew). The more pragmatic approach of experienced organic growers and conventional ones (higher doses and fewer sprays) reduced the yield losses. The proposed indicator is used for two purposes, i) evaluating the quantitative losses due to pest attacks and ii) differentiating them from other non-pest ones. A more detailed analysis including the impact on performance will be achieved and published soon

A Machine-Learning Approach for Classifying Defects on Tree Trunks using Terrestrial LiDAR

International audienceThree-dimensional data are increasingly prevalent in forestry thanks to terrestrial LiDAR. This work assesses the feasibility for an automated recognition of the type of local defects present on the bark surface. These sin-gularities are frequently external markers of inner defects affecting wood quality, and their type, size, and frequency are major components of grading rules. The proposed approach assigns previously detected abnormalities in the bark roughness to one of the defect types: branches, branch scars, epi-cormic shoots, burls, and smaller defects. Our machine learning approach is based on random forests using potential defects shape descriptors, including Hu invariant moments, dimensions, and species. The results of our experiments involving different French commercial species, oak, beech, fir, and pine showed that most defects were well classified with an average F 1 score of 0.86

Tree Defect Segmentation using Geometric Features and CNN

International audienceEstimating the quality of standing trees or roundwood after felling is a crucial step in forest production trading. The ongoing revolution in the forest sector resulting from the use of 3D sensors can also contribute to this step. Among them the terrestrial lidar scanning is a reference descriptive method offering the possibility to segment defects. In this paper, we propose a new reproducible method allowing to automatically segment the defects. It is based on the construction of a relief map inspired from a previous strategy and combining with a convolutional neural network to improve the resulting segmentation quality. The proposed method outperforms the previous results and the source code is publicly available with an online demonstration allowing to test the defect detection without any software installation

Le séchage combiné convection-micro-ondes : modelisation-validation-optimisation

Not availableCe travail est consacré à l'étude du séchage combiné convection-micro-ondes, le matériau choisi pour l'étude étant un béton cellulaire. Il comporte une partie théorique et une partie expérimentale. D’un point de vue théorique, deux points sont plus particulièrement discutés: la formulation du terme source volumique d'énergie et la modélisation des transferts de chaleur et de masse avec prise en compte du gradient de pression totale de la phase gazeuse. D’un point de vue expérimental, des mesures de perte de masse, de la quantité d'eau évacuée sous forme liquide, des températures et pressions internes ont été réalisées et sont comparées aux résultats théoriques. En parallèle, une étude a été menée sur le phénomène d'expulsion du liquide observable en début de séchage assisté par micro-ondes. Une expérience de drainage a été mise au point. Le modèle testé dans les mêmes conditions donne de bons résultats quantitatifs. En final, le logiciel est utilisé comme un outil d'optimisation, pour quantifier les gains de temps et d'énergie apportés par l'utilisation des micro-ondes en début et en fin de séchag

Warp modelling and validation for european pieces. Influence of relevant basic properties

International audienc

Comparaison de mesures et de simulations du gonflement de planchettes de chênes. Partie 2 : simulation et validation

National audienc

Comparaison de mesures et de simulations de gonflement de planchettes de chênes. Partie 1 : mesures de déformations

National audienc