La pousse courte feuillée, un indicateur du degré de différenciation chez le hêtre (Fagus sylvatica L.)

Chez le hêtre, aucun caractère morphologique externe permettant d'appréhender de manière continue l'évolution d'un individu d'un stade juvénile végétatif vers un stade adulte florifère n'a été mis en évidence. Les seuls éléments mentionnés sont des caractères ponctuels : la marcescence, révélateur d'un état juvénile et la floraison attestant de l'entrée dans la phase adulte. L'objectif de l'étude était de mettre en évidence plusieurs marqueurs morphologiques externes du degré de différenciation chez le hêtre en décrivant simultanément l'architecture des arbres et leurs pousses courtes feuillées d'un an. L'analyse révèle que la morphologie des pousses courtes évolue en fonction de leur localisation dans la plante, de l'âge de la plante et de l'environnement dans lequel celle-ci se développe. Elle révèle aussi que cette évolution est en rapport direct avec la croissance en hauteur des arbres, mais aussi avec le degré de complexité qu'ils atteignent au cours de leur développement. L'évolution des pousses courtes constitue un repère sur lequel la marcescence et la floraison, traduisant des potentialités internes de la plante, peuvent être repérés. (Résumé d'auteur

Predicting tropical forest stand structure parameters from Fourier transform of very high-resolution remotely sensed canopy images

1. Predicting stand structure parameters for tropical forests from remotely sensed data has numerous important applications, such as estimating above-ground biomass and carbon stocks and providing spatial information for forest mapping and management planning, as well as detecting potential ecological determinants of plant species distributions. As an alternative to direct measurement of physical attributes of the vegetation and individual tree crown delineation, we present a powerful holistic approach using an index of canopy texture that can be extracted from either digitized air photographs or satellite images by means of two-dimensional spectral analysis by Fourier transform. 2. We defined an index of canopy texture from the ordination of the Fourier spectra computed for 3545 1-ha square images of an undisturbed tropical rain forest in French Guiana. This index expressed a gradient of coarseness vs. fineness resulting from the relative importance of small, medium and large spatial frequencies in the Fourier spectra. 3. Based on 12 1-ha control plots, the canopy texture index showed highly significant correlations with tree density (R2 = 0·80), diameter of the tree of mean basal area (R2 = 0·71), distribution of trees into d.b.h. classes (R2 = 0·64) and mean canopy height (R2 = 0·57), which allowed us to produce reasonable predictive maps of stand structure parameters from digital aerial photographs. 4. Synthesis and applications. Two-dimensional Fourier analysis is a powerful method for obtaining quantitative characterization of canopy texture, with good predictive ability on stand structure parameters. Forest departments should use routine forest inventory operations to set up and feed regional databases, featuring both tree diameter figures and digital canopy images, with the ultimate aims of calibrating robust regression relationships and deriving predictive maps of stand structure parameters over large areas of tropical forests. Such maps would be particularly useful for forest classification and to guide field assessment of tropical forest resources and biodiversity

Structure des couronnes et variation de l’épaisseur et de la surface d’aubier chez l’Angélique deGuyane (Dicorynia guianensis Amsh., Caesalpinioideae, Fabaceae)

International audienceL'Angélique (Dicorynia guianensis Amsh.) représente environ 35% de laproduction de bois d'oeuvre en Guyane. Cependant, la stratégie de duraminisationdite ‘tardive’ chez cette essence entraîne une grande variabilité de l'épaisseurd'aubier (Fig. 1A) et par conséquent, influence la proportion exploitable de lagrume. La relation entre quantité de bois de coeur et diamètre à 1m30 (DBH) (e.g.Carrodus (1972), Wilkes (1991), Pinto et al. (2004), Wang et al. (2010)), ne permetpas une estimation suffisamment précise de la quantité de duramen et/ou d’aubier.A ce jour, très peu d’études mettent en lien la structure de la couronne et/ou lestatut social de l’individu avec la quantité de duramen (e.g. Pazdrowski et al.(2009), Nawrot et al. (2008)). Or, une grande diversité de structures des couronnesest observable au sein d’une même classe de diamètre (Fig. 1B).Ici, nous proposons une méthode visuelle et rapide de diagnostic architectural desarbres permettant d’améliorer l’estimation de la quantité de duramen dans letronc

Овочівництво причорномор’я України: сучасний стан галузі в контексті інноваційного розвитку

Метою дослідження є організаційно-економічні особливості виробництва овочевої продукції відкритого ґрунту та картоплі Причорноморського регіону та підвищення їх економічної ефективності на засадах інноваційного розвитку

Segmentation-based approaches for characterising plant architecture and assessing its plasticity at different scales

International audiencePlants are modular organisms that develop by the repetition of elementary botanical entities or constructional units through the three main and fundamental morphogenetic processes of growth, branching and reiteration (Barthélémy and Caraglio, 2007). Repetition of these entities induces gradual or abrupt changes in their characteristics. These characteristics are quantified through several variables, called the entity attributes. On the one hand, differences between entities reflect different stages of differentiation in the meristems (Nicolini and Chanson, 1999), which are ordered in time and correspond to the notion of physiological age of meristems (Barthélémy and Caraglio, 2007). The changes of one attribute through the plant structure are referred to as morphogenetic gradient. On the other hand, part of the entity differences can be imputed to environmental factors. Based on this botanical model of plant functioning, our approach jointly relies on categories of entities with similar characteristics, a description of those within-category characteristics and the category topological organisation within the plant. This constitutes a useful summary of the plant architecture, which is the basis for 1) highlighting hidden regularities in plant structures, for a better understanding of the gradients and organisation rules; 2) proposing and validating ecophysiological hypotheses, and new sampling protocols; 3) adopting a powerful paradigm for modelling plant development. In this work, the entity categories are identified using a hidden Markov tree (HMT) model, in which local dependencies only ( i.e. interactions between connected entities) are accounted for. This is not sufficient to accurately describe the topological distribution of the entities within the plant, and the changes of the plant topology. This is why various complementary methods and models (among which edit distance algorithms and sequence analysis using Markovian models), performed at different scales, are used in our approach to provide a more detailed description of the architecture, and to assess how various controlled factors affect architecture plasticity

Exploring morphogenetical gradient variability using hidden Markov tree models in young individuals of the tropical species Symphonia globulifera (Clusiaceae)

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