Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : Architectural analyses of temperate tree species using a chronological approach suggest that the expression of epicormic branches is closely related to low growth rates in the axes that make up the branching system. Therefore, sole consideration of epicormic criteria may be sufficient to identify trees with low secondary growth levels or with both low primary and secondary growth levels. In a tropical tree such as Dicorynia guianensis (basralocus), where chronological studies are difficult, this relationship could be very useful as an easily accessible indicator of growth potentials. A simple method of architectural tree description was used to characterize the global structure of more than 1650 basralocus trees and to evaluate their growth level. Measurements of simple growth characters [height, basal diameter, internode length of submittal part (top of the main axis of the tree)] and the observation of four structural binary descriptors on the main stem (presence of sequential branches and young epicormic branches, state of the submittal part, global orientation), indicated that epicormic branch formation is clearly related to a decrease in length of the successive growth units of the main stem. Analysis of height vs. diameter ratios among different tree subgroups, with and without epicormic branching, suggested that trees with epicormic branches generally have a low level of secondary growth compared with primary growth.
ISSN: 0305-7364

hal-01032037
https://hal.archives-ouvertes.fr/hal-01032037
DOI : 10.1093/aob/mcg119

Éditeur(s) : HAL CCSD National Research Council Canada
Résumé :  
Le développement de l'axe principal d'arbres de deux peuplements de chêne sessile âgés respectivement de 15 et 29 ans a été reconstitué par l'observation simultanée de marqueurs morphologiques et anatomiques de la croissance. La comparaison de la structure morphologique des pousses annuelles et des unités de croissance selon leur âge ontogénique ou leur année de formation a permis de dégager des tendances dues au stade de développement de la plante ou aux effets climatiques annuels. Au cours du développement, trois phases se distinguent. La première se traduit par la formation de pousses annuelles monocycliques de taille constante et correspond probablement à la présence du couvert forestier. Dans une seconde phase, les modalités de développement intrinsèques à l'arbre s'expriment en priorité ; le taux de polycyclisme, comme la longueur des pousses annuelles, augmente régulièrement d'une année sur l'autre, et on observe une forte différenciation entre les unités de croissance successives d'une même pousse annuelle bicyclique. Lors de la troisième phase, les facteurs environnementaux semblent avoir une influence plus marquée sur la croissance des individus. La longueur des différentes structures est stationnaire, malgré des fluctuations inter-annuelles. Les différences entre les deux unités de croissance successives des pousses annuelles bicycliques ne sont pas systématiques.
ISSN: 0008-4026

hal-01032105
https://hal.archives-ouvertes.fr/hal-01032105
DOI : 10.1139/cjb-78-3-361

Éditeur(s) : HAL CCSD Springer Verlag/EDP Sciences
Résumé : absent
ISSN: 1286-4560

hal-01032265
https://hal.archives-ouvertes.fr/hal-01032265
DOI : 10.1051/forest:2005048

Éditeur(s) : HAL CCSD
Résumé : Diffusion du document : INRA Documentation de Centre, Domaine de Duclos, 97170 Petitt-Bourg (Guadeloupe, France) Diplôme : DEA
il s'agit d'un type de produit dont les métadonnées ne correspondent pas aux métadonnées attendues dans les autres types de produit : DISSERTATION
Basralocus (Dicorynia guianensis Amshoff, Caesalpiniaceae), first timber exploited species in French Guyana, shows a spatial aggregative distribution. In order to characterize Basralocus clump organisation, many approaches were used : the study of different forest variables (total height, diameter at breast height, .... j, a spatial analysis studied by population splitting in 3 classes according to their diameters at breast height and an architectural analysis. To evaluate the pertinence of different approach, 2 clump structures, located on control and logged plots,are compared. The trees of the logged clump have a smaller height and diameter. a slender habit, a taller crown and a better growth than the control. These 2 clumps stand out by a different number of mature trees and different types of spatial distribution of juvenile trees around them are possible. The opening of the environment by forestry provokes a Jump rejuvenation by the presence of numerous unbranched young trees. The architectural analysis helps to detect a large expression variability in growth strategies which can be reflected by different architectural vigours. The combination between forest variables, spatial and architectural analysis results could suggest a dynamic evolution of these 2 clumps.
L'Angélique (Dicorynia guianensis Amshoff, Caesalpiniaceae), première espèce exploitée Pour le bois d'oeuvre en Guyane française, a une répartition spatiale de type agrégatif. Afin de caractériser la structure d’un agrégat d'Angélique, plusieurs approches sont utilisées: une étude des différents paramètres dendrométriques (hauteur totale, diamètre à 1.30 m....j. une analyse spatiale réalisée en découpant la population des individus en 3 classes de diamètre bien distinctes et une analyse architecturale. Afin de valider la pertinence de ces approches, 2 agrégats, l'un en parcelle témoin et l'autre en parcelle exploitée pour le bois d'oeuvre, sont comparés. Ainsi, les arbres de l'agrégat exploité ont une hauteur et un diamètre plus petit, un port plus élancé, un houppier plus grand et une meilleure croissance. Ces 2 agrégats se distinguent par un nombre variable de semenciers et différents types de répartition spatiale des juvéniles autour de ceux-ci sont possibles. L'ouverture du milieu par l'exploitation forestière provoque un rajeunissement de l'agrégat souligné par la présence de nombreux individus jeunes non ramifiés. L'analyse architecturale permet de déceler une grande variabilité d'expression dans le développement qui se traduit par différentes vigueurs architecturales. En combinant les résultats des analyses dendrométrique, spatiale et architecturale, une évolution dynamique de la structure de ces 2 agrégats est proposée.
https://hal.archives-ouvertes.fr/hal-01189192

hal-01189192
https://hal.archives-ouvertes.fr/hal-01189192
PRODINRA : 13161

Éditeur(s) : HAL CCSD Ecole nationale du génie rural
Résumé :  
Les forêts hétérogènes guyanaises sont des milieux complexes dont la gestion passe par la compréhension de leur organisation (structure spatiale, horizontale et verticale et diversité spécifique) et de leur dynamique. Dans ce contexte, l'étude des stratégies de développement et d'occupation de l'espace des arbres permet de mieux comprendre comment les différentes espèces exploitent et structurent l'hétérogénéité du milieu. Depuis une trentaine d'années, les travaux menés en architecture végétale ont permis d'établir un contexte méthodologique et conceptuel pour étudier la structure globale de l'arbre et pour comprendre les mécanismes morphologiques qui lui ont donné naissance. Après une présentation de concepts majeurs d'architecture végétale, cet article expose les méthodes employées pour quantifier la structure des arbres et les approches permettant d'intégrer les critères architecturaux dans un diagnostic à l'échelle du peuplement.
ISSN: 0035-2829

hal-01032084
https://hal.archives-ouvertes.fr/hal-01032084

Éditeur(s) : HAL CCSD Springer Verlag/EDP Sciences
Résumé : International audience
Context : Functional - structural models (FSM) of tree growth have great potential in forestry, but their development, calibration and validation are hampered by the difficulty of collecting experimental data at organ scale for adult trees. Due to their simple architecture and morphological properties, " model plants " such as Cecropia sciadophylla are of great interest to validate new models and methodologies, since exhaustive descriptions of their plant structure and mass partitioning can be gathered. * Aims : Our objective was to develop a model-based approach to analysing the influence of environmental conditions on the dynamics of trophic competition within C. sciadophylla trees. * Methods : We defined an integrated environmental factor that includes meteorological medium-frequency variations and a relative index representing the local site conditions for each plant. This index is estimated based on model inversion of the GreenLab FSM using data from 11 trees for model calibration and 7 trees for model evaluation. * Results : The resulting model explained the dynamics of biomass allocation to different organs during the plant growth, according to the environmental pressure they experienced. * Perspectives : By linking the integrated environmental factor to a competition index, an extension of the model to the population level could be considered.
ISSN: 1286-4560

hal-00780347
https://hal-ecp.archives-ouvertes.fr/hal-00780347
https://hal-ecp.archives-ouvertes.fr/hal-00780347/document
https://hal-ecp.archives-ouvertes.fr/hal-00780347/file/Letort2011AFS.pdf
DOI : 10.1007/s13595-011-0131-x

Éditeur(s) : HAL CCSD Wiley
Résumé : 1. Considerable debate surrounds the extent to which tropical forests can be managed for resource extraction while conserving biodiversity and ecosystem properties, which depend on functional composition. Here we evaluate the compatibility of these aims by examining the effects of logging on taxonomic and functional diversity and composition in a tropical forest. 2. Twenty years after selective logging, we inventoried 4140 stems regenerating in logging gaps and adjacent undisturbed areas, and we integrated a database of 13 functional traits describing leaf and wood economics of tropical trees. 3. We found no differences in taxonomic and functional richness among habitats, but logging gaps had significantly higher taxonomic and functional evenness. 4. Logging also effected striking, long-term changes in both species and functional composition. In particular, the xylem density of recruits in logging gaps was 6% less than in unlogged forests, leaves were 11% less tough and had 613% greater mineral nutrient concentrations. 5. Synthesis and applications. Our results suggest that managers of tropical forests should limit overall surface area converted to logging gaps by creating fewer, larger gaps during selective logging, to reduce impacts on the taxonomic and functional composition of the regenerating stand.
ISSN: 0021-8901

hal-01032420
https://hal.archives-ouvertes.fr/hal-01032420
DOI : 10.1111/j.1365-2664.2012.02164.x

Éditeur(s) : HAL CCSD
Résumé : International audience
Over the past decade, much attention has been devoted to the development of forest biomass estimation methods at a stand scale, leading to the establishment of allometric models (Chave et al., 2014). These allometric equations use a unique wood specific gravity value (WSG) per species, but neglect the within tree variations of WSG found by others (Wiemann & Williamson, 1989).The main objectives of this study are (1) to illustrate the diversity of radial (from pith to bark) and longitudinal (from bottom to top) patterns of WSG variation within and between species, (2) to highlight different trends of WSG radial variations and the possible misinterpretations of these trends due to the effect of heartwood and (3) to link these variations and patterns to the successional status of the species (from pioneer to sciaphilic species).We sampled 33 small trees (10 Wood sciences underpinning tropical ecology and management. International closing symposium of the XYLAREDD project.
Tervuren, Belgium

hal-01188894
https://hal-sde.archives-ouvertes.fr/hal-01188894

Éditeur(s) : HAL CCSD
Résumé : The relation between primary and secondary growth has been traditionally studied in terms of growth units and has always being assumed as closely correlated. Pluviometric variation directly affects growth patterns in the neotropical pioneer species Jacaranda copaia. In French Guiana this species produces annual growth rings in the dry season that can be seen with the naked eye.The morphological and anatomical description of three monocaulous individuals was made node by node. The trees where felled at a roadside locality close to the city of Kourou, French Guiana. The comparison of intermodal distance, pith transversal area and wood ring area variation within an individual elucidates the origin of well-known problems in dendrochronological analysis of tropical trees.The wood found close to the pith, known as young wood, always has false wood rings; the production of these rings is correlated with short intermodal distances and small pith transversal area. This phenomenon seems to be caused by minor intrannual pluviometric variation that affects both primary and secondary growth. This new methodological approach helps morphologists and anatomists interpret growth patterns in tropical trees in a more holistic way.
Botany 2010
Rhode Island, United States

hal-01032389
https://hal.archives-ouvertes.fr/hal-01032389

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Forest successional processes following disturbance take decades to play out, even in tropical forests. Nonetheless, records of vegetation change in this ecosystem are scarce, increasing the importance of the chronosequence approach to study forest recovery. However, this approach requires accurate dating of secondary forests, which until now was a difficult and/or expensive task. Cecropia is a widespread and abundant pioneer tree genus of the Neotropics. Here we propose and validate a rapid and straightforward method to estimate the age of secondary forest patches based on morphological observations of Cecropia trees. We found that Cecropia-inferred ages were highly correlated with known ages of the forest. We also demonstrate that Cecropia can be used to accurately date disturbances and propose twenty-one species distributed all over the geographical range of the genus as potential secondary forest chronometer species. Our method is limited in applicability by the maximal longevity of Cecropia individuals. Although the oldest chronosequence used in this study was 20 years old, we argue that at least for the first four decades after disturbance, the method described in this study provides very accurate estimations of secondary forest ages. The age of pioneer trees provides not only information needed to calculate the recovery of carbon stocks that would help to improve forest management, but also provides information needed to characterize the initial floristic composition and the rates of species remigration into secondary forest. Our contribution shows how successional studies can be reliably and inexpensively extended without the need to obtain forest ages based on expensive or potentially inaccurate data across the Neotropics.
ISSN: 1932-6203

halsde-00757518
https://hal.archives-ouvertes.fr/halsde-00757518
DOI : 10.1371/journal.pone.0042643
PUBMED : 22916144

Éditeur(s) : HAL CCSD
Résumé : International audience
BackgroundTree above ground biomass (AGB) is currently estimated by tree-level allometrical models that take into account, tree volume estimated from proxy variables of tree size (DBH) and species average wood specific gravity (WSG). These methods are common and realistic from a practical point of view. However, they do not take into account deviance from fixed allometrical trajectories and species or tree level WSG variations. Here, we present Xtrawood software that allows computation of tree AGB according to structure and WSG variations.MethodXtrawood reconstructs tree structure and integrates WSG variations by merging tree structure and WSG data measured at different position in trees, leading to the computation of global AGB and visualization of WSG variation along tree structure. Tree structure is measured according to stem dimensions (length, diameter) and positions within tree, and encoded in Multiscale Tree Graph format (MTG). WSG data is made of radial WSG profiles (1 measure each 0,5 cm from pith to bark) sampled at different heights within whole tree. Xtrawood output are illustrated using a dataset collected on an Amazonian forest ‘biomass dominant species’, Dicorynia guianensis Amsh., also known to exhibit substantial WSG gradients along both radial and vertical axis. 9 trees ranging from 15 to 60 cm DBH were measured by climbers. Each tree was felled and samples were collected at different positions (3 in trunk, 1 to 5 in crown) to record WSG radial profiles.ResultsXtrawood allows computation of tree volume, but also visualization of WSG variations in tree as well as inference of WSG radial profiles at different heights. Output variables are decomposed according to different tree scale and locations (axis, trunk/crown) and easy to extract. Xtrawood results will be compared to those of standard estimation method and can be used to identify positions in trees where WSG value leads to the better estimate of tree AGB.Conclusion/perspectiveXtrawood produces AGB estimate with data from intensive measurements practices. The sampling protocol, used here, remains destructive and time-consuming because Xtrawood is not directly dedicated to forest managers, but to help calibration of realistic sampling strategies. Moreover, Xtrawood offers a way to understand relationships between tree development, WSG variations within tree structure and biomass accumulation in the context of natural forests or plantations. A software demo is available at coffee break.
53rd Annual Meeting of the Association for Tropical Biology and Conservation (ATBC 2016)
Montpellier, France

Droits : http://creativecommons.org/licenses/by/
hal-01349613
https://hal.archives-ouvertes.fr/hal-01349613

Éditeur(s) : HAL CCSD
Résumé : The genus Cecropia includes pioneer trees that colonize canopy gaps and cleared areas. It is widely distributed from Mexico to Northern Argentina. Cecropia trees have architecture, which corresponds to the Rauh’s architectural model. In recent studies we have found that C. obtusa/ and C. sciadophylla, in French Guiana, have a strong annual periodicity for growth, branching and flowering processes, with annual emission of 35 nodes for C. obtusa and 25 for C. sciadophylla. Those species show different life histories since C. sciadophylla has longer life expectancy. In addition, C. sciadophylla is found more frequently in forest gaps, although in French Guiana mixed populations are found. The aim of this work was to compare developmental strategies of both species in three different field stations in French Guiana and to determine how these two species coexist during its first years of life. We studied a 20-year old population of /C. sciadophylla/ at Saint Elie’s Road, a 10-year old population of /C. obtusa/ at Paracou’s field station, and a 7-year old mixed population at Counami’s Road. /C. sciadophylla /emits 25 nodes per year in both studied populations, while/ C. obtusa /emits 35 nodes in the monospecific population and 30 nodes in the mixed population. In the monocaule stage, the lower number of nodes emitted by /C. sciadophylla/ compared to /C. obtusa /is compensated with a higher internodal length, which allows finding individuals with similar ages and lengths, but different number of nodes. The branching and flowering processes start on average three years before in /C. obtusa/, however for 12-year old individuals we observed a dominancy of C. sciadophylla over C. obtusa. In the mixed population it is likely that the different life histories would decrease competition effects allowing coexistence of both species during the first stages of life
Botany 2008
Vancouver, Canada

hal-01190209
https://hal.archives-ouvertes.fr/hal-01190209
PRODINRA : 182910

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Heartwood/sapwood profile and the tradeoff between trunk and crown increment in a natural forest: the case study of a tropical tree (Dicorynia guianensis Amsh., Fabaceae) Key message Sapwood area and the radial growth rate of the trunk follow the same pattern at breast height, with an initial increase and subsequent constant value, resulting from the increasing growth allocation toward the crown rather than tree decline. Heartwood area and heartwood volume in the trunk increase more rapidly after this shift occurs. Abstract Sapwood (SW) and heartwood (HW) are two functionally distinct classifications of wood in perennial stems for which quantities can vary greatly in tropical trees. Numerous positive correlations have been found between the radial growth rate (RGR) and SW quantity; however, variations in the SW/HW quantities have not been studied in light of the ontogenetic variation of RGR. Wood core sampling, intensive measurements of tree structure (number of branches, stem volumes), and radial growth monitoring were performed on an abundant and highly exploited tree species in French Guiana (Dicorynia guianensis) to investigate the relationship between RGR, SW/HW quantity, tree structure, and their variations on the course of a tree's ontogeny. SW area and RGR followed the same pattern of variation throughout tree development, both increasing first and reaching a steady state after 50 cm DBH (diameter at breast height). After this value, we observed a strong increase in both the HW area and HW volume increment, concomitant with a more rapid increase in crown volume. The stabilization of RGR for trees with DBH >50 cm was related not to a tree's decline but rather to an increasing wood allocation to the crown, confirming that RGR at breast height is a poor indicator of whole-tree growth for bigger individuals. We also confirmed that HW formation is an ontogenetic process managing SW quantity that is continuously and increasingly produced within the crown as the tree grows. This study highlights the effect of growth-mediated ontogenetic changes on the localization of water and carbohydrate storage within a tree, resulting from SW and HW dynamics throughout tree ontogeny.
ISSN: 0931-1890

hal-01654003
https://hal.archives-ouvertes.fr/hal-01654003
https://hal.archives-ouvertes.fr/hal-01654003/document
https://hal.archives-ouvertes.fr/hal-01654003/file/Lehnebach%20et%20al.%E2%80%94Trees%202016-%20Own%20version.pdf
DOI : 10.1007/s00468-016-1473-7

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Decreasing growth rate (Feeley et al., 2007) and large die-back due to drought (Phillips et al., 2009) suggest that tropical forests are suffering recent climate changes. Forest vulnerability to external factors (e.g. air pollution, acid rain) is widely studied in northern countries, while only a few attempts have investigated crown integrity in the Tropics. The method needs to be generic enough to account for the large number of species and crown shapes encountered in tropical forests. In the present study, we developed and tested a novel field method that estimates crown fragmentation (main branch mortality (MB) and secondary branch mortality (SB)), liana infestation (LI) and crown position (CP) in the canopy. The relationship between crown fragmentation and annual growth rate (agr) was investigated through multiple regression. Six out of eight canopy tree species showed significant growth decline with increasing crown fragmentation. Higher probability of death was also found in trees with severe crown fragmentation. The capacity of such crown assessment to depict tree vitality in a forest stand is discussed along with potential applications in both forest science and management
ISSN: 0378-1127

halsde-00611465
https://hal.archives-ouvertes.fr/halsde-00611465
DOI : 10.1016/j.foreco.2010.10.025

Éditeur(s) : HAL CCSD
Résumé : In a recent study based on a retrospective reconstruction of growth, we showed for Cecropia sciadophylla that branching and flowering processes, as well as alternation of long and short nodes were regularly spaced by ~23 nodes. We also found that this strong periodicity was related to an annual cycle of growth. Adult trees are successful individuals that have reached the canopy and our previous results were found in adult trees, suggesting that variability in the number of nodes produced per year is underestimated, because the degree of variation decreases with age. Here, we hypothesized that growth periodicity could be related to rainfall and we focus on two C. sciadophylla populations with contrasting precipitation seasonality. During 19 months and for 69 saplings, we measured growth at regular monthly intervals to test the intra-annual variability in the number of nodes produced per month and per year. We also characterized the intra-annual fluctuations in the number of present leaves in the main axis and internode lengths among months. We found that node elongation and number of present leaves in the main axis vary among months in the population subjected to a strong seasonal precipitation. In contrast, the population subjected to a non-seasonal precipitation showed smaller variation in node elongation and no variation in the number of leaves presented in the main axis among months. Regardless the population of origin, we also found that ~23 was the number of nodes produced per year and that the time required to produce a new node was ~15 days at any month of the year. The strong stability in the average number of nodes produced per month and per year among populations, suggests a genetically controlled trait. In spite of a strong genetic determination on the number of nodes produced per year, several environmental factors, including rainfall, could be the cause of the observed variation in elongation and number of present leaves in the main axis.INRAUM2
Botany 2010
Rhode Island, United States

hal-01191343
https://hal.archives-ouvertes.fr/hal-01191343
PRODINRA : 178581

Éditeur(s) : HAL CCSD Cambridge University Press (CUP)
Résumé : Patterns of leaf production and leaf fall directly influence leaf area index and forest productivity. Here, we focused on Cecropia sciadophylla individuals inhabiting the extremes of the gradient in seasonality in rainfall at which C. sciadophylla occurs. In Colombia and French Guiana we compared the intra-annual variation in leaf production as well as the intra-annual fluctuation in internode length on a total of 69 saplings ranging in size from 1 to 2 m. The mean rate of leaf production was similar to 2 leaves mo(-1) in both populations, and the rate of leaf production was constant throughout the year. Our results showed monthly variation in internode length and the number of live leaves per sapling in the seasonal habitat and variation only in internode length in the everwet habitat. Because the rate of leaf production is constant at both localities, the difference in number of live leaves per sapling at the seasonal site must reflect seasonal variation in leaf life span. We show that in Cecropia, internode length can serve as an indicator of precipitation seasonality. Finally an open question is whether leaf production in other pioneer species is also independent of climatic seasonal cues. This information could allow us to link growth and climate of secondary forest species and better understand how past and future climate can affect plant growth trajectories.
ISSN: 0266-4674

hal-01032402
https://hal.archives-ouvertes.fr/hal-01032402
DOI : 10.1017/S0266467413000394

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
ISSN: 1100-9233

hal-01092514
https://hal-agroparistech.archives-ouvertes.fr/hal-01092514
DOI : 10.1111/j01654-1103.2010.01175.x

Éditeur(s) : HAL CCSD Linnean Society of London
Résumé : International audience
The circumscription of Salicaceae has recently been enlarged to include a majority of the species formerly placed in the polyphyletic tropical family Flacourtiaceae. Several studies have reported a peculiar and infrequently formed multilayered structure of tension wood in four of the tropical genera. Tension wood is a tissue produced by trees to restore their vertical orientation, and most studies have focused on trees developing tension wood by means of cellulose-rich, gelatinous fibres, as is known in Populus L. and Salix L. (Salicaceae s.s.). This study aims to determine if the multilayered structure of tension wood is an anatomical characteristic common in other Salicaceae, and if so, how its distribution correlates to phylogenetic relationships. Therefore, we studied the tension wood of 14 genera of Salicaceae as well as two genera of Achariaceae, one genus of Goupiaceae, and one genus of Lacistemataceae, families closely related to Salicaceae or formerly placed in Flacourtiaceae. Opposite wood and tension wood were compared with light microscopy and 3D Laser Scanning Confocal Microscopy. The results indicate that a multilayered structure of tension wood is common in the family except in Salix, Populus, and one of their closest relatives, Idesia polycarpa Maxim. We suggest that tension wood may be a useful anatomical character in understanding phylogenetic relationships in Salicaceae. Further investigation is still needed on the tension wood of several other putatively close relatives of Salix and Populus, in particular Bennettiodendron Merr., Macrohasseltia L.O.Williams and Itoa Hemsl.
ISSN: 0024-4074

hal-01392845
https://hal.archives-ouvertes.fr/hal-01392845
https://hal.archives-ouvertes.fr/hal-01392845/document
https://hal.archives-ouvertes.fr/hal-01392845/file/GhislainEtAl2016_MultylayerTWSalicaceae_Bot_Jsur the_Lin_Soc_HALssfig.pdf
DOI : 10.1111/boj.12471

Éditeur(s) : HAL CCSD
Résumé : Le genre Cecropia regroupe des arbres pionniers, à croissance rapide, qui colonisent les aires défrichées et les milieux ouverts à fort ensoleillement. Leur architecture est relativement simple et conforme au modèle de Rauh. Tout au long de la vie de la plante il est possible de retrouver a posteriori les cicatrices de feuille, d’inflorescences et de branches élaguées. En décrivant les axes noeuds à noeuds il est possible de construire des séquences d’événements ou l’index est le métamère et les variables associées la longueur de l’entre-noeud, la présence de fleurs, de branches, ou de leurs cicatrices. En analysant ces séquences avec des outils statistiques issus de l’analyse des séries temporelles il est possible de mettre en évidence des régularités structurelles (par ex: nombres de noeuds séparant 2 étages de branches) et de proposer une interprétation sur l’organisation dans le temps des processus de croissance, ramification et floraison qui mène à l’édification de l’architecture des représentants de cette espèces. C’est en suivant cette démarche que de récents travaux menés en Guyane française sur C. obtusa et C. sciadophylla ont démontré une forte périodicité annuelle pour les processus de croissance, de floraison et de ramification chez deux espèces. Le fait le plus remarquable est la grande régularité dans le nombre de feuilles émises chaque année avec 35 noeuds pour C. obusa et 25 noeuds pour C. sciadophylla. Cette régularité peut permettre déterminer l’âge d’un individu et de retrouver sa croissance passée. Dans ce travail nous avons voulu aborder la diversité et la plasticité de ces règles de construction en comparant des populations de C. sciadophylla ayant poussé dans des environnements variés en Guyane Française (2 populations) et en Colombie (4 populations). Les résultats montrent que le nombre de feuilles allongées chaque année est remarquablement stable pour l’ensemble des populations et est égal 25. La floraison est annuelle pour la majorité des individus mesurés mais il est cependant possible d’observer 2 floraisons par an chez certains arbres de Guyane. Les paramètres les plus variables concernent l’âge et la hauteur avant la première ramification ou la de la première floraison ainsi que les allométries entre la hauteur et le diamètre. Le lien entre cette variabilité et les conditions environnementales tel que la pluviométrie, la fertilité des sols ou la compétition seront discutés.
La plasticité phénotypique des arbres
Montpellier, France

hal-01190210
https://hal.archives-ouvertes.fr/hal-01190210
PRODINRA : 182912

Éditeur(s) : HAL CCSD
Résumé : International audience
FSPM07 - 5th International Workshop on Functional-Structural Plant Models
Napier, New Zealand

hal-00847590
https://hal.inria.fr/hal-00847590