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Stand-level wind damage can be assessed using diachronic photogrammetric canopy height models / Jean-Pierre Renaud in Annals of Forest Science, vol 74 n° 4 (December 2017)  

Public [article]  inAnnals of Forest Science > vol 74 n° 4 (December 2017) Titre : Stand-level wind damage can be assessed using diachronic photogrammetric canopy height models Type de document : Article/Communication Auteurs : Jean-Pierre Renaud , Auteur ; Cédric Vega , Auteur ; Sylvie Durrieu, Auteur ; Jonathan Lisein , Auteur ; Magnussen, Steen, Auteur ; Philippe Lejeune, Auteur ; Meriem Fournier, Auteur Année de publication : 2017 Projets : FOR-WIND / Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] analyse diachronique [Termes IGN] appariement dense [Termes IGN] dommage matériel [Termes IGN] hauteur des arbres [Termes IGN] image aérienne [Termes IGN] modèle numérique de surface de la canopée [Termes IGN] photogrammétrie [Termes IGN] placette d'échantillonnage [Termes IGN] semis de points [Termes IGN] tempête [Termes IGN] volume en bois [Vedettes matières IGN] Inventaire forestier Résumé : (auteur) Key message : Diachronic photogrammetric canopy height models can be used to quantify at a fine scale changes in dominant height and wood volume following storms. The regular renewal of aerial surveys makes this approach appealing for monitoring forest changes. Context : The increasing availability of aerial photographs and the development of dense matching algorithms open up new possibilities to assess the effects of storm events on forest canopies. Aims : The objective of this research is to assess the potential of diachronic canopy height models derived from photogrammetric point clouds (PCHM) to quantify changes in dominant height and wood volume of a broadleaved forest following a major storm. Methods : PCHMs derived from aerial photographs acquired before and after a storm event were calibrated using 25 field plots to estimate dominant height and volume using various modeling approaches. The calibrated models were combined with a reference damage maps to estimate both the within-stand damage variability, and the amount of volume impacted. Results : Dominant height was predicted with a root mean squared error (RMSE) of 4%, and volume with RMSEs ranging from 24 to 32% according to the type of model. The volume impacted by storm was in the range of 42–76%. Overall, the maps of dominant height changes provided more details about within-stand damage variability than conventional photointerpretation do. Conclusion : The study suggests a promising potential for exploiting PCHM in pursuit of a rapid localization and quantification of wind-throw damages, given an adapted sampling design to calibrate models. Numéro de notice : A2017-733 Affiliation des auteurs : LIF+Ext (2012-2019) Thématique : FORET Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s13595-017-0669-3 En ligne : https://doi.org/10.1007/s13595-017-0669-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=88546 [article]

Wind loads and competition for light sculpt trees into self-similar structures / Christophe Eloy in Nature communications, vol 8 (2017)  

Public [article]  inNature communications > vol 8 (2017) Titre : Wind loads and competition for light sculpt trees into self-similar structures Type de document : Article/Communication Auteurs : Christophe Eloy, Auteur ; Meriem Fournier, Auteur ; André Lacointe, Auteur ; Bruno Moulia, Auteur Année de publication : 2017 Langues : Anglais (eng) Descripteur : [Termes IGN] arbre (flore) [Termes IGN] croissance des arbres [Termes IGN] données allométriques [Termes IGN] modèle numérique [Termes IGN] rayonnement lumineux [Termes IGN] structure de la végétation [Termes IGN] vent [Vedettes matières IGN] Botanique Résumé : (auteur) Trees are self-similar structures: their branch lengths and diameters vary allometrically within the tree architecture, with longer and thicker branches near the ground. These tree allometries are often attributed to optimisation of hydraulic sap transport and safety against elastic buckling. Here, we show that these allometries also emerge from a model that includes competition for light, wind biomechanics and no hydraulics. We have developed MECHATREE, a numerical model of trees growing and evolving on a virtual island. With this model, we identify the fittest growth strategy when trees compete for light and allocate their photosynthates to grow seeds, create new branches or reinforce existing ones in response to wind-induced loads. Strikingly, we find that selected trees species are self-similar and follow allometric scalings similar to those observed on dicots and conifers. This result suggests that resistance to wind and competition for light play an essential role in determining tree allometries. Numéro de notice : A2017-780 Affiliation des auteurs : non IGN Thématique : FORET Nature : Article DOI : 10.1038/s41467-017-00995-6 En ligne : https://doi.org/10.1038/s41467-017-00995-6 Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=88980 [article]

Within-stem maps of wood density and water content for characterization of species: a case study on three hardwood and two softwood species / Fleur Longuetaud in Annals of Forest Science, vol 73 n° 3 (September 2016)  

Public [article]  inAnnals of Forest Science > vol 73 n° 3 (September 2016) . - pp 601 - 614 Titre : Within-stem maps of wood density and water content for characterization of species: a case study on three hardwood and two softwood species Type de document : Article/Communication Auteurs : Fleur Longuetaud, Auteur ; Frédéric Mothe, Auteur ; Meriem Fournier, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 601 - 614 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Végétation [Termes IGN] Abies alba [Termes IGN] Acer pseudoplatanus [Termes IGN] analyse discriminante [Termes IGN] caractérisation [Termes IGN] densité du bois [Termes IGN] espèce végétale [Termes IGN] Fagus sylvatica [Termes IGN] Pseudotsuga menziesii [Termes IGN] Quercus (genre) [Termes IGN] teneur en eau de la végétation [Termes IGN] tomographie [Termes IGN] tronc Résumé : (auteur) Key message : Variability and interrelations between wood density, water content, and related properties were analyzed by CT scanning of five species. Relative water content of lumens is proposed as the best complement to basic specific gravity for discrimination of species with respect to their functioning. Context : X-ray computed tomography (CT) is an efficient tool for analysis of wood properties related to density and water content all along a tree stem. Basic specific gravity, an inherent property of the wood material, is well known and widely used in wood sciences. Aims : The first aim of this study was to describe a method for mapping a set of wood properties within a tree stem. The second objective was to analyze the relations among these properties and to identify the one that offers the best information in addition to basic specific gravity for discrimination of species. Methods : Wood discs were collected at various heights along a tree stem. We used a method consisting of comparing the CT images of the discs in the green state and after oven drying. Finally, 10 variables were computed for 115 trees of five temperate species: green, oven-dry, and basic specific gravities; moisture content; relative water content; relative water content of lumens; and fractions of air, water, free water, and cell walls. Results : Maps of wood properties summarizing the radial and vertical variations were obtained, allowing us to highlight species-specific patterns. The five species were discriminated best when plotted in the plane defined by basic specific gravity and relative water content of lumens. Conclusion : The proposed method is original and simple enough to process large samples. Because it correlated less with basic specific gravity than with moisture content, relative water content of lumens was selected for species characterization. This is the first study of such wood properties at this fine scale within a tree stem, simultaneously and for a substantial number of trees of five species including both hardwoods and softwoods. Numéro de notice : A2016-710 Affiliation des auteurs : non IGN Thématique : FORET Nature : Article DOI : 10.1007/s13595-016-0555-4 Date de publication en ligne : 20/05/2016 En ligne : https://doi.org/10.1007/s13595-016-0555-4 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=82088 [article]

Pas de vent, pas de bois. L’apport de la biomécanique des arbres pour comprendre la croissance puis la vulnérabilité aux vents forts des peuplements forestiers / Meriem Fournier in Revue forestière française, vol 67 n° 3 (mai 2015)  

Public [article]  inRevue forestière française > vol 67 n° 3 (mai 2015) . - pp 213 - 237 Titre : Pas de vent, pas de bois. L’apport de la biomécanique des arbres pour comprendre la croissance puis la vulnérabilité aux vents forts des peuplements forestiers Type de document : Article/Communication Auteurs : Meriem Fournier, Auteur ; Vivien Bonnesoeur, Auteur ; Christine Deleuze, Auteur ; et al., Auteur Année de publication : 2015 Article en page(s) : pp 213 - 237 Note générale : bibliographie Langues : Français (fre) Descripteur : [Vedettes matières IGN] Végétation [Termes IGN] arbre (flore) [Termes IGN] changement climatique [Termes IGN] données environnementales [Termes IGN] peuplement forestier [Termes IGN] phytobiologie [Termes IGN] tempête [Termes IGN] vent Résumé : (auteur) La biomécanique étudie les réactions et adaptations des êtres vivants à leur environnement mécanique, par exemple aux oscillations et forces exercées par le vent. Au-delà des théories anciennes de la sécurité mécanique constante, la mécanobiologie a récemment formalisé les signaux mécaniques, la perception des cellules vivantes et les réponses de croissance. Ces mécanismes physiologiques font que l’arbre ne forme vraiment du bois, tissu de soutien, que lorsqu’il est mécaniquement stimulé. La croissance est contrôlée par les déformations mécaniques perçues, qui deviennent alors pour l’arbre de bons indicateurs de sécurité. Pour appliquer ces connaissances aux forêts, le projet ANR FOR-WIND a l’ambition de développer une mécanobiologie adaptée aux temps longs et aux conditions naturelles complexes. L’enjeu est de concevoir les pratiques d’aménagement avec de nouveaux indicateurs de vulnérabilité aux vents forts, qui raisonnent l’effet du changement climatique, de la structure du paysage, de la sylviculture ou de l’amélioration génétique au travers des processus clés mais négligés d’endurcissement des arbres aux vents usuels. Numéro de notice : A2015-836 Affiliation des auteurs : non IGN Thématique : FORET Nature : Article DOI : 0.4267/2042/58173 En ligne : https://doi.org/10.4267/2042/58173 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79142 [article]

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Large-scale dynamics of a heterogeneous forest resource are driven jointly by geographically varying growth conditions, tree species composition and stand structure / Holger Wernsdörfer in Annals of Forest Science, Vol 69 n° 7 (October 2012)  

Public [article]  inAnnals of Forest Science > Vol 69 n° 7 (October 2012) . - pp 829 - 844 Titre : Large-scale dynamics of a heterogeneous forest resource are driven jointly by geographically varying growth conditions, tree species composition and stand structure Type de document : Article/Communication Auteurs : Holger Wernsdörfer, Auteur ; Antoine Colin , Auteur ; Jean-Daniel Bontemps , Auteur ; Hélène Chevalier, Auteur ; Gérôme Pignard, Auteur ; Sylvain Caurla, Auteur ; Jean-Michel Leban , Auteur ; Jean-Christophe Hervé (1961-2017) , Auteur ; Meriem Fournier, Auteur Année de publication : 2012 Article en page(s) : pp 829 - 844 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Statistiques [Termes IGN] composition floristique [Termes IGN] croissance des arbres [Termes IGN] espèce végétale [Termes IGN] gestion forestière durable [Termes IGN] grande échelle [Termes IGN] inventaire forestier national (données France) [Termes IGN] strate végétale Résumé : (auteur) Context: Forest resource projections are required as part of an appropriate framework for sustainable forest management. Suitable large-scale projection models are usually based on national forest inventory (NFI) data. However, sound projections are difficult to make for heterogeneous resources as they vary greatly with respect to the factors that are assumed to drive forest dynamics on a large spatial scale, e.g. geographically varying growth conditions (here represented by NFI regions), tree species composition (here broadleaf-dominated, conifer-dominated and broadleaf-conifer mixed stands) and stand structure (here high forest, coppice forest and high-coppice forest mixture). Question and objective: Our question was how does the variance of forest dynamics parameters (i.e. growth, felling and mortality, and recruitment processes) and that of 20-year forest resource projections partition between these factors (NFI region, tree species composition and stand structure), including their interactions. Our objective was to capitalise on the suitability of an existing multi-strata, diameter class matrix model for the purposes of making projections for the highly heterogeneous French forest resource. Methods: The model was newly calibrated for the entire territory of metropolitan France based on most recent NFI data, i.e. for years 2006–2008. The forest resource was divided into strata by crossing the factors NFI region, tree species composition and stand structure. The variance partitioning of the parameters and projections was assessed based on a model sensitivity analysis. Results: Growth, felling and mortality varied mainly with NFI region and species composition. Recruitment varied mainly with NFI region and stand structure. All three factors caused variations in resource projections, but with unequal intensities. Factor impacts included first order and interaction effects. Conclusions: We found, by considering both first order and interaction effects, that NFI region, species composition and stand structure are ecologically relevant factors that jointly drive the dynamics of a heterogeneous forest resource. Their impacts, in our study, varied depending on the forest dynamics process under consideration. Recruitment would appear to have a particularly great impact on resource changes over time. Numéro de notice : A2012-717 Affiliation des auteurs : IGN+Ext (2012-2019) Thématique : FORET Nature : Article DOI : 10.1007/s13595-012-0196-1 Date de publication en ligne : 22/03/2012 En ligne : https://doi.org/10.1007/s13595-012-0196-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=75562 [article]

Les contraintes de croissance dans les tiges : modélisation de leur mise en place et de leur fonction biologique / Tancrède Alméras in Revue forestière française, vol 60 n° 6 (novembre - décembre 2008)  

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