Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
In this work we perform a statistical analysis of global solar radiation measured at two sites, 38 km distant from, in Guadeloupe, French West Indies. We have established a correlation model based on the coefficient of variation assuming a time scale separation. The coefficient of variation is calculated on minutes interval with data measured at 1 Hz. This analysis highlight the dynamic correlation that can occur between measurements from two different sites with a time step of one second. From this results, knowing the coefficient of variation on a site we have established a new correlation model on this parameter for another site. A diagram linking the standard deviation on both sites, for a given coefficient of variation is proposed for correlated and non-correlated cases. More over this analysis put in evidence the existence of a threshold time under which there is no significant correlation. This model can be useful in choosing new sites of production not only for establishing correlation from on site to another, but also in optimizing the geographical distribution of the solar farms within the territory.
ISSN: 0960-1481

Droits : http://hal.archives-ouvertes.fr/licences/copyright/
hal-01099045
https://hal.archives-ouvertes.fr/hal-01099045
https://hal.archives-ouvertes.fr/hal-01099045/document
https://hal.archives-ouvertes.fr/hal-01099045/file/Article%20Foison_2014.pdf

Éditeur(s) : HAL CCSD American Society for Microbiology
Résumé : International audience
A rapid and specific high-performance liquid chromatography method with UV detection (HPLC-UV) for the simultaneous determination of 12 beta-lactam antibiotics (amoxicillin, cefepime, cefotaxime, ceftazidime, ceftriaxone, cloxacillin, imipenem, meropenem, oxacillin, penicillin G, piperacillin, and ticarcillin) in small samples of human plasma is described. Extraction consisted of protein precipitation by acetonitrile. An Atlantis T3 analytical column with a linear gradient of acetonitrile and a pH 2 phosphoric acid solution was used for separation. Wavelength photodiode array detection was set either at 210 nm, 230 nm, or 298 nm according to the compound. This method is accurate and reproducible (coefficient of variation [CV] < 8%), allowing quantification of beta-lactam plasma levels from 5 to 250 μg/ml without interference with other common drugs. This technique is easy to use in routine therapeutic drug monitoring of beta-lactam antibiotics.
ISSN: 0066-4804

hal-00875271
https://hal.archives-ouvertes.fr/hal-00875271
https://hal.archives-ouvertes.fr/hal-00875271/document
https://hal.archives-ouvertes.fr/hal-00875271/file/Simultaneous_Determination-accepted.pdf
PUBMED : 21788467

Éditeur(s) : Gauthier-Villars
Résumé : The variability of ''yellow substance'' in waters of the Skagerrak and the Kattegat was studied during the international Skagex programme in 1990 and 1991. Data on attenuation of light and fluorescence of dissolved organic matter (DOM) in sea water were collected with a spectral transmissiometer and a submersible fluorometer within a depth range of 0-250 m at several stations. More than fifty-fold variations of fluorescence intensity over space and time were due to the combined action of different sources of DOM in the straits. The surface maximum of fluorescing DOM, related to river outflow, was spreading from Oslo fjord to the central Skagerrak in late spring. This maximum may be ecologically important because it diminishes shortwave PAR. In the autumn the brightest DOM fluorescence was found in the Kattegat and along the Norwegian coast in accordance with earlier studies. The local minima of DOM fluorescence are associated with the Jutland current. Both the instability of the current and a ten-fold difference in DOM content between deep layers of the Skagerrak and Kattegat resulted in strong synoptic variability of fluorescence in the transitional area between the straits. Seasonal and synoptic variabilities of ''yellow substance'' were minimal in the southern Kattegat. The vertical gradients of DOM fluorescence were mostly negative at the depth of the thermocline of the open Skagerrak in spring, reaching values of 40-50 % m-1. Fine structure and complex shape were inherent to fluorescence profiles from areas of intensive water mixing. DOM fluorescence closely covaried with attenuation of UV light: the correlation coefficient was + 0.9 for wavelength w <= 350 nm regardless of season. The inverse dependence between wavelength derivative and magnitude of UV attenuation in the straits did not change with season. DOM fluorescence and water salinity were negatively correlated at depths of 25-50 m but they varied independently in the upper 10 m. No significant correlation between fluorescence and nitrates has been found. Estimates of correlation with phosphates ranged from 0.7 to 0.8. In general, the changes of fluorescence were due to variations of DOM content in sea water but not to variability of DOM composition or state. The properties of DOM fluorescence in the Skagerrak-Kattegat area make it a useful natural tracer of water movements suitable for active remote sensing with airborne lidar.
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1993 , Vol. 16 , N. 2 , P. 115-125

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00099/21041/18667.pdf
http://archimer.ifremer.fr/doc/00099/21041/

Éditeur(s) : Elsevier
Résumé : The New Caledonia blue shrimp Litopenaeus stylirostris is commercially produced under semi-intensive rearing conditions. The size of the farming earthen ponds (5–10 ha) and the subsequent production constraints make it difficult to use them as experimental units for random experiments. Moreover, since every pond has its own characteristics, ponds' effects cannot be ruled out, thus making it hard to define true replicates. In order to design future experiments under conditions resembling those used in production, we evaluated the possible use of floating cages as experimental units with the aim of assessing treatment effects with a reasonable statistical power. To this end, two sets of floating cages were placed respectively in two different ponds in a commercial farm. In both cases the zootechnical conditions in the cages were similar in post-larvae origin, management, and diet and feeding regime. The aim of the study was to evaluate on a technical basis the possibility of rearing shrimps in floating cages set up in earthen ponds and to assess this method from a statistical standpoint. Shrimps reared in and outside the cages showed comparable growth and survival rates. The variability in the zootechnical parameters between cages, expressed as the estimated coefficient of variation (CV) for survival rate, total final biomass (g), final body weight (g), daily increment in body weight (g day− 1) and FCR were 11.0, 13.7, 4.4, 5.4, and 7.0%, respectively. On the basis of these figures, we calculated for a given statistical power (80%) the number of replicates (cages) that would be required to reveal significant differences between two treatments, at a 5% level of significance. We found that for expected differences of 20% from the control mean, 3 and 6 floating cages per treatment would be reasonable to determine statistical differences for growth parameters and survival rate, respectively. Moreover, we showed a significant pond effect in regard to survival and growth between the two sets of cages. These results illustrated the within-farm variability among the ponds, and confirmed that the specific characteristics of each pond from the same farm make it difficult to use the ponds themselves as experimental units. The study demonstrates that rearing in floating cages is an economical, powerful and sensitive experimental tool for shrimp culture studies specifically carried out under conditions close to semi-intensive production.
Aquaculture (0044-8486) (Elsevier), 2008-07 , Vol. 279 , N. 1-4 , P. 63-69

Droits : 2008 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/2008/publication-4363.pdf
DOI:10.1016/j.aquaculture.2008.03.053
http://archimer.ifremer.fr/doc/00000/4363/

Éditeur(s) : Université du Littoral Côte d'Opale (Dunkerque)
Résumé : In the Bay of Biscay and Celtic Sea waters, hake is considered as genetically homogeneous and form a unique stock with identical meristic characteristics. The vertebral mean vary from 50,68 (vertebrae) during the first year of life to 51,11 (vertebrae) for adults. 0-group Merluccius display a rapid growth with significant interannual variability (0.71 mm.day-1 in 2001 versus 0.74 mm.day-1 in 2002). The spawning period occurs in April and the average length on the firth January following the hatching is of 17.3 cm (first seasonal check / increment on the sagittal otolith is located about 0.143 cm from the nucleus). At the end of the first year of life the average length is about 24 cm. The longevity of the species is important and growth parameters (L = 138,24 cm ; K = 0,132) explain natural mortality coefficient of M = 0.21. No difference for growth between male and female has been observed for this stock. The ratio total weight / eviscerated weight is equal to Fc = 1,086. Both male and female have same spatial and bathymetric distribution. Juveniles are found in deep waters (< 17 cm length) and move to coastal waters where they display an average length of (33 cm length). Longer individuals are found in nursery areas where they feed and grow then move to deeper areas to spawn. Nursery areas are numerous and located in the Celtic Sea and in the bay of Biscay. In the bay of Biscay, disturbances resulted from hydrondynamics affect the settlement on the nursery grounds particularly in the southern part of the bay. Diet composition varies with age. Juveniles feed mainly on crustaceans (Euphausia kroni). At the length of 23 cm, individuals feed strictly on fishes. Sizes of preys are proportional with sizes of predators and preys are composed mainly of species that feed and reproduce close to the bottom. Cannibalism has been observed for this specie, and increases with age notably in the northern part of the bay of Biscay and in the Celtic Sea. Main preys are 0-group juveniles. This specie is assumed to be a passive predator catching its preys when they come to feed in the bottom. Although they are punctual, these results have been obtained after studies on the evolution of sizes during the first year of life (daily increments measurements) and on the spawning period parameters (back-calculating). Average length on the firth January following hatching and the position of the first seasonal check on the otolith are based on observations of the sizes on the firth January following hatching (obtained with growth rates and spawning period parameters). The results are similar to those described in previous studies, nevertheless they have to be confirmed with growth and diet composition analyses. A long term study appear essential to determine biological and ecological parameters of this species for sustainable management of the stock.
Les alertes quant à la surexploitation du stock de merlu européen sont nombreuses et récurrentes. Seulement l'estimation du niveau réel de l'état du stock a toujours posé des problèmes du fait de certaines lacunes dans la connaissance de la biologie et de l'écologie de cette espèce. Dans les eaux du golfe de Gascogne et de la mer Celtique, le merlu européen fait partie de la même population génétique et possède les mêmes caractéristiques meristiques. Sa moyenne vertébrale est de 50,68 durant sa première année de vie et évolue pour se stabiliser à 51,11 chez l'adulte. La croissance du merlu durant sa première année de vie et très rapide mais présente une variabilité interannuelle significative (0,71 mm .J-1 en 2001 et 0,74 mm .J-1 en 2002). Sa période de ponte maximale se déroule au mois d'avril et sa longueur au premier janvier suivant sa naissance est de 17,3 cm (la première marque hivernale est positionnée à 0,143 cm du nucléus de la sagittae). Au terme de sa première année de vie le merlu atteint une longueur de 24 cm. Sa longévité est assez longue (23 ans environ) et ses paramètres de croissance (L = 138,24 cm ; K = 0,132) permettent d'estimer son coefficient de mortalité naturelle à M = 0,21. Il n'a pas été établi de croissance différentielle entre sexe chez le merlu dans ces eaux. Le rapport poids total / poids éviscéré a été estimé à Fc = 1,086. Mâles ou femelles, les merlus ont une même répartition spatiale et bathymétrique. En général, ils sont très profonds à leurs stades juvéniles (< 17 cm) et ils se dirigent vers les eaux côtières pour les atteindre à 33 cm de longueur environ. Au-delà de cette taille, les merlus se concentrent au niveau des zones de nourricerie pour s'y alimenter avant de rejoindre les eaux plus profondes pour y pondre. Les zones de nourricerie du merlu sont très nombreuses et sont localisées en mer Celtique et dans le golfe de Gascogne aussi bien dans sa partie sud que dans sa partie nord. Les perturbations importantes dans l'hydrodynamisme du golfe de Gascogne (upwelling) semble influencer les niveaux de colonisation des zones de nourricerie notamment celles situées dans la partie sud du golfe. Le régime alimentaire du merlu évolue avec l'âge. Juvénile, il se nourrit principalement de crustacés (Euphausia krohni) et devient ichtyophage exclusif dès 23 cm de longueur. Le cannibalisme est une réalité chez le merlu et les merlus-proies sont les juvéniles du groupe d'âge G-0. Il s'intensifie avec l'âge notamment dans la partie nord du golfe de Gascogne et en mer Celtique ; Il est très faible dans le sud du golfe de Gascogne. La taille des proies évolue avec la taille du merlu et les poissons proies sont en général des espèces qui vont se nourrir ou se reproduire sur le fond. Ce comportement alimentaire fait que le merlu est un prédateur peu actif et qui attaque ses proies lorsqu'elles viennent sur le fond. Ces résultats, bien qu'ils ne soient que ponctuels, ont été obtenus après avoir déterminé le schéma d'évolution de la longueur du merlu durant sa première année de vie (dénombrement des accroissement journaliers) et des paramètres de sa période de ponte (rétro-calcul).La taille au premier hiver et la position de la première marque hivernale ont été déterminées en relativisant nos observations à l'estimation de la longueur du merlu au premier janvier suivant sa naissance : celle-ci étant obtenue en utilisant le taux de croissance et les paramètres de la période de ponte. Bien que l'ensemble des résultats obtenus, en ce qui concerne la répartition spatiale et les données sur la période de ponte, soient généralement conformes à ceux décrits dans la littérature, il est nécessaire de confirmer ceux concernant la croissance et le régime alimentaire. Pour cela, une étude à plus long terme semble indispensable pour parvenir à bien maîtriser l'ensemble des paramètres de biologie et d'écologie du merlu permettant ainsi une meilleure gestion de son stock.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2004/these-1247.pdf
http://archimer.ifremer.fr/doc/00000/1247/

Éditeur(s) : HAL CCSD Springer Verlag (Germany)
Résumé : International audience
The anisotropy of vibrational properties influences the acoustic behaviour of wooden pieces and their dependence on grain angle (GA). As most pieces of wood include some GA, either for technological reasons or due to grain deviations inside trunks, predicting its repercussions would be useful. This paper aims at evaluating the variability in the anisotropy of wood vibrational properties and analysing resulting trends as a function of orientation. GA dependence is described by a model based on transformation formulas applied to complex compliances, and literature data on anisotropic vibrational properties are reviewed. Ranges of variability, as well as representative sets of viscoelastic anisotropic parameters, are defined for mean hardwoods and softwoods and for contrasted wood types. GA-dependence calculations are in close agreement with published experimental results and allow comparing the sensitivity of different woods to GA. Calculated trends in damping coefficient (tanδ) and in specific modulus of elasticity (E′/ρ) allow reconstructing the general tanδ-E′/ρ statistical relationships previously reported. Trends for woods with different mechanical parameters merge into a single curve if anisotropic ratios (both elastic and of damping) are correlated between them, and with axial properties, as is indicated by the collected data. On the other hand, varying damping coefficient independently results in parallel curves, which coincide with observations on chemically modified woods, either “artificially”, or by natural extractives.
Wood Science and Technology

hal-01096868
https://hal-agroparistech.archives-ouvertes.fr/hal-01096868
DOI : 10.1007/S00226-010-0393-8

Éditeur(s) : Université de Bretagne Occidentale
Résumé : Study of mineral suspended particulate matter (SPM) is essential to understand ecosystem dynamics. SPM influences light penetration which is closely related to primary production and carries pollutants and nutrients within the water masses. This work aims to study near-surface mineral SPM dynamics in the English Channel using two complementary methods: remote-sensing by satellites and numerical modelling. Firstly, MODIS and MERIS satellite images processed by the IFREMER semi-analytical algorithm and describing non-algal SPM, are analysed to build three statistical models which are able to estimate near-surface SPM using simple variables, e.g., tidal coefficient, significant wave height and mean chlorophyll-a concentration. Secondly, the three-dimensional hydrosedimentary model ROMS (Regional Ocean Modeling System) is applied in the English Channel. It considers tidal forcing along open boundaries, wind stress at the sea-surface, wave-current interactions in the bottom boundary layer and realistic heterogeneous bottom sediments. Results of the more sophisticated statistical model is also used to impose SPM concentrations at open boundaries. Sensitivity tests on SPM boundary conditions show the importance of prescribing realistic sediment concentrations to improve the model predictions. Biological influences on mineral SPM are also tested using settling velocity and critical shear stress for erosion which vary with seasons. Both statistical and numerical models highlight and locate respective influences of tide, waves and biology on mineral SPM. Numerical predictions indicate that near-surface SPM is mainly composed of silts (>70%). Near-surface suspended silts come largely from seabed resuspension alongshore in the Eastern Channel and from the open boundaries of our limited-area coastal model at the West of Cotentin Peninsula and offshore. Near-surface SPM variations are investigated at semi-diurnal, neap-spring tidal cycle time scales and during a wave event. Finally, dynamics of sediments in the turbidity maximum zone around the Isle of Wight is examined depending on hydrodynamical conditions in order to distinguish the role played by advection and local erosion/settling processes in this area. Keywords: Suspended particulate matter, satellite, remote-sensing, modelling, English Channel, sediments, turbidity, tide, wave
L'étude des matières en suspension (MES) minérales est essentielle pour comprendre le fonctionnement des écosystèmes en Manche : les MES influencent la pénétration de la lumière dans la colonne d'eau, paramètre clé pour la production biologique, et sont susceptibles de transporter des polluants et nutriments. Lors de ce travail, la dynamique des MES minérales de surface en Manche est étudiée à l'aide de deux méthodes complémentaires : l'observation par satellite et la modélisation numérique tridimensionnelle. Dans un premier temps, les images satellite MODIS et MERIS, traitées par l'algorithme semi-analytique développé par l'IFREMER et représentant les MES non-algales de surface, sont analysées afin d'élaborer trois modèles statistiques permettant d'estimer la MES de surface en fonction de variables basiques telles que le coefficient de marée, la hauteur significative des vagues et la concentration moyenne en chlorophylle-a. Dans un deuxième temps, le modèle hydrosédimentaire multiclasse tridimensionnel ROMS (Regional Ocean Modeling System) est implémenté en Manche. Il prend en considération le forçage par la marée aux frontières ouvertes, la contrainte exercée par le vent à la surface de la mer, l'interaction houle-courant en couche limite de fond et l’hétérogénéité spatiale réaliste du lit sédimentaire. Les résultats du modèle statistique le plus sophistiqué sont également utilisés pour forcer la concentration en MES aux frontières ouvertes du domaine de calcul. Des tests de sensibilité sur les conditions limites montrent l'importance de considérer de manière réaliste les sédiments entrant en Manche par les frontières ouvertes lors de la modélisation numérique. L'influence de la biologie sur les MES minérales est testée en utilisant une formulation de la vitesse de chute et de la contrainte critique d'érosion variant saisonnièrement. Grâce à ces deux outils associés, les influences respectives de la marée, de la houle et de la biologie sur les MES minérales sont mises en avant et localisées en Manche. Le modèle numérique prédit que les MES de surface sont composées principalement de silts (>70%). Les silts en suspension en surface proviennent majoritairement du lit sédimentaire près des côtes en Manche orientale et des frontières ouvertes du domaine de calcul à l'ouest de la presqu'île du Cotentin et au large en Manche centrale et orientale. Les variations des MES de surface sont ensuite étudiées aux échelles des cycles de marée semi-diurnes, vive-eau/morte-eau et autour d'un épisode de houles. Enfin, l'évolution de la concentration de sédiments dans la zone de forte turbidité autour de l'île de Wight peut être analysée suivant les conditions hydrodynamiques afin d'évaluer les rôles respectifs des processus locaux d'érosion/dépot et d'advection dans la génération de ces turbidités remarquables. Mots-clés : Matière en suspension, télédétection, satellite, modélisation, Manche, sédiments, turbidité, marée, houle

Droits : 2013 UBO
http://archimer.ifremer.fr/doc/00157/26783/24884.pdf
http://archimer.ifremer.fr/doc/00157/26783/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
In this work we perform a statistical analysis of global solar radiation measured at two sites, Petit Canal and Pointe a Pitre, 38 km distant from, Guadeloupe, French West Indies. We have established a correlation model based on the coefficient of variation assuming a time scale separation. The coefficient of variation is calculated on 10 min interval with data measured at 1 Hz. This analysis highlights the dynamic correlation that can occur between measurements from two different sites with a time step of 1 s. From these results, knowing the coefficient of variation on a site, we have established a new correlation model on this parameter for another site. A diagram linking the standard deviation for the studied sites, for a given coefficient of variation is proposed for correlated and non-correlated cases. Moreover this analysis evidences the existence of a threshold time under which there is no significant correlation. The methodology and the model can be applied to any other sites to establish diagrams of the coefficient of variation.This model can be useful in choosing new sites of PV production in establishing correlation from on site to another
ISSN: 0960-1481

hal-01528078
https://hal.archives-ouvertes.fr/hal-01528078
DOI : 10.1016/j.renene.2015.10.049

Éditeur(s) : HAL CCSD
Résumé : International audience
We consider a second-order differential system with Hessian-driven damping . An interesting property of this system is that, after introduction of an auxiliary variable y , it can be equivalently written as a first-order system in time and space. This allows us to extend the analysis to the case of a convex lower semicontinuous potential and so to introduce constraints in the model. When considering the indicator function of a closed convex set, the subdifferential operator takes account of the contact forces. In this setting, by playing with the geometrical damping parameter, we can describe nonelastic shock laws with restitution coefficient. Taking advantage of the infinite dimensional framework, we introduce a nonlinear hyperbolic PDE describing a damped oscillating system with obstacle. The system is dissipative; in the convex case each trajectory weakly converges to a minimizer of the global potential energy function. Exponential stabilization is obtained under strong convexity assumptions.
Differential Equations & Applications

hal-00803214
https://hal.archives-ouvertes.fr/hal-00803214
https://hal.archives-ouvertes.fr/hal-00803214/document
https://hal.archives-ouvertes.fr/hal-00803214/file/Attouch-Mainge-Redont-30August2011.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Recent research has demonstrated the importance of dermal exposure for some semivolatile organic compounds (SVOCs) present in the gas phase of indoor air. Though models for estimating dermal intake from gaseous SVOCs exist, their predictions can be subject to variations in input parameters, which can lead to large variation in exposure estimations. In this sensitivity analysis for a steady state model, we aimed to assess these variations and their determinants using probabilistic Monte Carlo sampling for 8 SVOCs from different chemical families: phthalates, bisphenols, polycyclic aromatic hydrocarbons (PAHs), organophosphorus (OPs), organochlorines (OCs), synthetic musks, polychlorinated biphenyls (PCBs) and polybromodiphenylethers (PBDEs). Indoor SVOC concentrations were found to be the most influential parameters. Both Henry's law constant (H) and octanol/water partition coefficient (Kow) uncertainty also had significant influence. While exposure media properties such as volume fraction of organic matter in the particle phase (fom-part), particle density (ρpart), concentration ([TSP]) and transport coefficient (ɣd) had a slight influence for some compounds, human parameters such as body weight (W), body surface area (A) and daily exposure (t) make a marginal or null contribution to the variance of dermal intake for a given age group. Inclusion of a parameter sensitivity analysis appears essential to reporting uncertainties in dermal exposure assessment.
ISSN: 0160-4120

hal-01635769
https://hal.archives-ouvertes.fr/hal-01635769
https://hal.archives-ouvertes.fr/hal-01635769/document
https://hal.archives-ouvertes.fr/hal-01635769/file/Pelletier%202017%20Dermal%20expo%20rev2.pdf
DOI : 10.1016/j.envint.2017.02.005

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Le but de cette étude est de relier les variations des descripteurs de structure (densité du peuplement, surface terrière, biomasse aérienne) et de dynamique (croissance des arbres, taux de mortalité et de recrutement, flux de biomasse) de la forêt tropicale à la surface des parcelles forestières et à l'intervalle de temps entre les inventaires forestiers. Un jeu de données provenant d'un large réseau de parcelles recensé tous les 2 ans sur une période de 16 ans a été utilisé pour développer et paramétrer un nouveau modèle statistique de prédictions des coefficients de variations pour chacun des descripteurs étudiés. Plus de 90 % de la variabilité de ces coefficients de variation est prédit par un modèle statistique qui inclut la taille de la parcelle et l'intervalle de temps entre les inventaires. Tous les descripteurs de structure de la forêt varient de moins de 10% pour des parcelles de taille supérieure à 2 ha. Parmi les descripteurs de la dynamique forestière, le flux sortant de biomasse aérienne est le plus variable. Cinq parcelles de 6.25 ha sont nécessaires pour estimer sa moyenne, sur une période 16 ans, avec une erreur de 20 % sur la moyenne. Ceci contraste avec un flux entrant de biomasse aérienne, via la croissance et le recrutement, relativement constant. La croissance des arbres est remarquablement bien estimée avec moins de 15 % de variabilité pour une parcelle de 2 ha recensée tous les 2 ans. Ce travail fournit une méthode facile de quantification des limitations des jeux de données utilisés pour estimer les descripteurs de structure et de dynamique forestière. Ceci est un prérequis indispensable à l'analyse des effets du changement global sur les forêts tropicales.
ISSN: 0006-3606

hal-01093212
https://hal-agroparistech.archives-ouvertes.fr/hal-01093212
DOI : 10.1111/j.1744-7429.2010.00644.x

Éditeur(s) : HAL CCSD Wiley
Résumé : A standardized rapid inventory method providing information on both tree species diversity and aboveground carbon stocks in tropical forests will be an important tool for evaluating efforts to conserve biodiversity and to estimate the carbon emissions that result from deforestation and degradation (REDD). Herein, we contrast five common plot methods differing in shape, size, and effort requirements to estimate tree diversity and aboveground tree biomass (AGB). We simulated the methods across six Neotropical forest sites that represent a broad gradient in forest structure, tree species richness, and floristic composition, and we assessed the relative performance of methods by evaluating the bias and precision of their estimates of AGB and tree diversity. For a given sample of forest area, a several small' (<1ha) sampling strategy led to a smaller coefficient of variation (CV) in the estimate of AGB than a few large' one. The effort (person-days) required to achieve an accurate AGB estimate (<10% CV), however, was greater for the smallest plots (0.1ha) than for a compromise approach using 0.5ha modified Gentry plots, which proved to be the most efficient method to estimate AGB across all forest types. Gentry plots were also the most efficient at providing accurate estimates of tree diversity (<10% CV of Hill number). We recommend the use of the 0.5ha modified Gentry plot method in future rapid inventories, and we discuss a set of criteria that should inform any choice of inventory method.
ISSN: 0006-3606

hal-01032408
https://hal.archives-ouvertes.fr/hal-01032408
DOI : 10.1111/btp.12006

Éditeur(s) : Amer Geophysical Union
Résumé : Sea surface salinity (SSS) measured from space by the Soil Moisture and Ocean Salinity (SMOS) mission is validated in the subtropical North Atlantic Ocean. 39 transects of ships of opportunity equipped with thermosalinographs (TSG) crossed that region from 2010 to 2012, providing a large database of ground truth SSS. SMOS SSS is also compared to Aquarius SSS. Large seasonal biases remain in SMOS and Aquarius SSS. In order to look at the capability of satellite SSS to monitor spatial variability, especially at scales less than 300 km (not monitored with the Argo network), we first apply a monthly bias correction derived from satellite SSS and In Situ Analysis System (ISAS) SSS differences averaged over the studied region. Ship SSS averaged over 25 km is compared with satellite and ISAS SSS. Similar statistics are obtained for SMOS, Aquarius and ISAS products (root mean square error of about 0.15 and global correlation coefficient r of about 0.92). However, in the above statistics, SSS varies due to both large scale and mesoscale (here, for scales around 100 km) variability. In order to focus on mesoscale variability, we consider SSS anomalies with respect to a monthly climatology. SMOS SSS and Aquarius SSS anomalies are more significantly correlated (r > 0.5) to TSG SSS anomaly than ISAS. We show the effective gain of resolution and coverage provided by the satellite products over the interpolated in situ data. We also show the advantage of SMOS (r=0.57) over Aquarius (r=0.52) to reproduce SSS mesoscale features.
Journal Of Geophysical Research-oceans (0148-0027) (Amer Geophysical Union), 2014-12 , Vol. 119 , N. 12 , P. 8878-8896

Droits : 2014. American Geophysical Union. All Rights Reserved.
http://archimer.ifremer.fr/doc/00210/32150/34082.pdf
DOI:10.1002/2013JC009610
http://archimer.ifremer.fr/doc/00210/32150/

Éditeur(s) : HAL CCSD Springer Verlag/EDP Sciences
Résumé : International audience
The vibration damping coefficient (tanδ) of wood is an important property for acoustical uses, including musical instruments. Current difficulties in the availability of some of the preferred species call for diversification, but this comes up against the lack of systematic damping coefficient data. * Keeping in mind the possible factors affecting tanδ, could we predict its variations between species, by using indicators that are either easily measured and/or readily available for many species? * Vibrational properties, equilibrium moisture content and colorimetric parameters were assessed on 94 wood types belonging to 76 species. Experimental results were then related to data on chemical contents and physical properties from the CIRAD database. The "standard" relationship between tanδ and specific modulus of elasticity (E'/ρ) explained only half of the variations. Deviations from this trend were correlated to extractives content, yet effects were not directly quantitative. Damping deviations were also correlated to colour and moisture-related properties, especially so with fibre saturation point. * By taking into account a combination of moisture-related properties, colour - or extractives content, and the "standard" relationship between tanδ and E'/ρ, we could propose simple predictive models which explain up to 89% of observed variations in tanδ between 48 species.
ISSN: 1286-4560

hal-00808338
https://hal.archives-ouvertes.fr/hal-00808338
https://hal.archives-ouvertes.fr/hal-00808338/document
https://hal.archives-ouvertes.fr/hal-00808338/file/Physico-chemical_indicators_Bremaud_al.pdf
DOI : 10.1051/forest/2010032

Éditeur(s) : HAL CCSD De Gruyter
Résumé : International audience
This study aims at better understanding the respective influences of specific gravity (γ), microfibril angle (MFA), and cell-wall matrix polymers on viscoelastic vibrational properties of wood in axial direction. The wide variations of properties between normal wood (NW) and compression wood (CW) are in focus. Three young bent trees (Picea abies, Pinus sylvestris and Pinus pinaster) that recovered verticality were sampled. Several observed differences between NW and CW were highly significant in terms of anatomical, physical (γ, shrinkage, CIELab colorimetry), mechanical (compressive strength), and vibrational properties. Specific dynamic modulus of elasticity (E'/γ) decreases with increasing MFA, and Young's modulus (E') can be satisfactorily explained by γ and MFA. Apparently, the type of the cell wall polymer matrix is not influential in this regard. The damping coefficient (tanδ) does not depend solely on MFA of NW and CW. The tanδ - E'/γ relationship evidences that, at equivalent E'/γ, the tanδ of CW is approx. 34% lower than that of NW. This observation is ascribed to the more condensed nature of CW lignins, and this is discussed in the context of previous findings in other hygrothermal and time/frequency domains. It is proposed that the lignin structure and the amount and type of extractives, which are both different in various species, are partly responsible for taxonomy-related damping characteristics.
ISSN: 0018-3830

hal-00808062
https://hal.archives-ouvertes.fr/hal-00808062
https://hal.archives-ouvertes.fr/hal-00808062/document
https://hal.archives-ouvertes.fr/hal-00808062/file/Changes_viscoelastic_vibrational_Bremaud_al.pdf
DOI : 10.1515/hf-2011-0186

Éditeur(s) : HAL CCSD
Résumé : International audience
ABSTRACT :A satellite retrieval of surface solar irradiance (SSI) based on GOES satellite data is presented and validated for the French Guiana with three years of in situ measurements from six ground stations. We propose a particle filter approach combining GOES satellite observations and in situ data. We propose an original observation function based on a joint probability distribution and taking advantages of the characteristics of both the involved type of data. The statistical results are compared with those of existing estimation methods and they are found to be in accordance with them. The daily bias ranges from -12 W/m² (-6% of the mean of measurements) to 12 W/m² (6%), depending on the stations. The daily root mean square difference ranges between 23 W/m² (10%) and 27 W/m² (15%). The correlation coefficient is close to 0.92. There is no seasonal climatic effect on the method, the bias and RMSD remain similar for both the rainy and the dry season, but better correlation is observed in the rainy season than in the dry season. Uncertainties are mainly due to the presence of specific tropical atmospheric conditions during the dry season. The method has been tested through various tests: cross-validation scheme has highlighted the potential generalization of the model in a temporal dimension; the ability of the method to effectively duplicate anomalies in surface solar irradiance time series has also been tested. The robustness of the results shows the interest of the method compared to other existing estimation methods. Because of its simplicity of implementation this method opens new prospects in estimating surface solar irradiance. It is concluded that using a particle filter and original observation function method allow a high-quality surface solar irradiance estimation in French Guiana.RESUMEUne méthode d'estimation de l'irradiance solaire de surface (SSI) à partir de données satellites GOES est présentée et validée par comparaison avec trois années de mesures in situ provenant de six stations météorologiques de Guyane Française. Dans cet article, nous proposons une approche par filtre particulaire combinant observations du satellite GOES et données in situ. Nous proposons une fonction d'observation originale basée sur une distribution de probabilité conjointe des deux types de données. Les résultats statistiques sont conformes à ceux des méthodes existantes. Le biais journalier varie de -16 W / m² (-7% de la moyenne des mesures) à 12 W / m² (6%). L'erreur quadratique moyenne (RMSD) est comprise entre 23 W / m² (10%) et 27 W / m² (15%). Le coefficient de corrélation est de 0,92. La méthode est peu sensible aux variations climatiques saisonnières, le biais et RMSD restent similaires en saison des pluies comme en saison sèche, mais une meilleure corrélation est observée pendant la saison des pluies. Les incertitudes sont principalement dues à la présence de conditions atmosphériques tropicales spécifiques en saison sèche. La méthode a été soumise à différents tests : un processus de validation croisée a mis en évidence la possible généralisation du modèle dans une dimension temporelle, la capacité du modèle à reproduire efficacement des anomalies dans les séries temporelles d'irradiance solaire de surface a aussi été testée. La robustesse des résultats obtenus montrent l'intérêt du modèle par rapport aux autres méthodes d'estimation existantes. A cause de sa simplicité de mise en oeuvre cette méthode ouvre de nouvelles perspectives en matière d'estimation de l'irradiance solaire au sol. Nous concluons que l'utilisation d'un filtre particulaire combinée à une fonction d'observation originale permet une estimation de haute qualité de l'irradiance solaire au sol en Guyane Française.
Canadian Journal of Remote Sensing

meteo-01304574
https://hal-meteofrance.archives-ouvertes.fr/meteo-01304574
DOI : 10.1080/07038992.2015.1040150

Résumé : L'importance des forêts tropicales dans le cycle du carbone à l'échelle planétaire est majeure, tant en terme de stock qu’en terme de flux de CO2. Plusieurs études mettent en évidence des changements au sein des forêts tropicales au cours des 20 dernières années, notamment des changements de la dynamique forestière et une augmentation de la biomasse aérienne. Les déterminants de ces variations sont aujourd’hui discutés et nous proposons ici d’apporter une contribution à ce débat. Les données utilisées dans ce travail proviennent du dispositif de suivi forestier à long terme de Paracou, Guyane Française, mis en place en 1984 et qui recouvre plus de 120 ha de forêt tropicale humide. Les données météorologiques proviennent de la tour à flux du dispositif, Guyaflux. Les mesures de diamètre proviennent de la base Guyafor pour les données annuelles et bisannuelles, et des mesures de 260 arbres à proximité de la tour à flux pour les mesures diamétriques intra-annuelles.Cette thèse se divise en deux grandes parties. La première concerne l’analyse de la biomasse du dispositif de suivi forestier de Paracou en Guyane et l’implication des changements de structure de cette forêt sur le bilan de carbone. Cette partie est constituée de deux points. (i) Quelles échelles temporelles et spatiales sont pertinentes pour analyser les composantes de structure (biomasse, aire basale et nombre de tiges) et de dynamique (croissance, recrutement et mortalité) des forêts tropicales afin de minimiser les effets d’échantillonnage ? Nous avons établi une méthodologie permettant de relier les intervalles de temps et la surface de mesure aux coefficients de variation de chacune des variables de structure et de dynamique de la forêt. (ii) Quels processus démographiques sont prépondérants dans l’explication des variations de biomasse et comment se redistribue la biomasse accumulée dans le système ? L’augmentation de la biomasse observée sur le dispositif de Paracou serait liée à la rareté des évènements de mortalité des gros arbres qui portent une part très importante de la biomasse.La deuxième partie de la thèse concerne l’analyse de l’effet du climat à moyen terme, inter et intra-annuel, et les effets directs du climat dans les changements de dynamique de la forêt. Cette partie se divise en 3 points. (i) Comment quantifier le stress hydrique en forêt tropicale humide ? Nous avons réalisé un modèle journalier de réserve en eau du sol pour les arbres en forêt tropicale. (ii) Quelles variables sont explicatives de la croissance des arbres en forêt guyanaise ? Nous avons montré que l’eau dans le sol est le facteur le plus explicatif du déterminisme climatique parmi un panel de variables climatiques. (iii) Quels traits fonctionnels sont prédicteurs de la réponse des arbres aux variations climatique ? Nous avons déterminé que des traits spécifiques, densité du bois et la hauteur maximale, ainsi que le diamètre de l'arbre au moment de la mesure, modulent la croissance des arbres en réponse au climat.
At a global scale tropical forest play a major role in term of carbon stock as well as in term of CO2 fluxes. Several studies have highlighted changes in tropical forest functioning during the last 20 years including a faster turnover and an increase of above ground biomass. The drivers of these changes are discussed and throughout this thesis we propose to contribute to this debate. We use the data from the Paracou experimental site in French Guiana established in 1984 on 120 hectares of moist tropical forest. Meteorological data come from the flux tower of the site, Guyaflux. We use annual and bisannual diameter measurements from the Guyafor database, and intra-annual diameter increments from the measurements of 260 trees near the flux tower.This thesis has two main parts. In the first part we present the biomass analysis of the Paracou permanent plots and the impact of structural changes in this forest on the carbon budget. The first part is constituted by two points. (i) Which temporal and spatial scale used to analyze the structure (biomass, basal area and stem density) and dynamics (tree growth, recruitment and mortality)components of tropical forest in order to minimized sample bias ? We establish a simple method to rely measurement interval between census and surface of measurement to the coefficient of variation of forests structure and dynamic components (ii) Which demographic process are involved in the explanation of biomass variation and how the biomass is distributed in the system ? The observed increase of biomass at Paracou could be link to the rarity of big trees mortality events. These big trees represent the larger part of the biomass. In the second part, we present the analysis of intra and inter-annual climate variation effects on forest dynamic changes. This part is divided in two points. (i) How to model drought stress in moist tropical forest ? We built a daily water balance model for tropical trees. (ii) Which climate variables explain the tree growth in guianian forests? We shown that soil water availability is the determinant factor of tree growth among a panel of climate variables. (iii) Which functional traits are involved in the tropical tree growth responses to climate? In this analysis, we determined that wood specific gravity, maximum tree height and tree diameter modulate the tree growth response to climate variations.

http://www.theses.fr/2011AGUY0481/document

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Radial trends of vibrational properties, including the specific dynamic modulus (E'/r) and damping coefficient (tand), were investigated for 3 tropical rainforest hardwood species, Simarouba amara, Carapa procera and Symphonia globulifera by free-free flexural vibration test. The microfibril angle (MFA) was estimated through X-Ray diffraction. Consistent patterns of radial variations were observed for all studied properties. E'/r was found to decrease from pith to bark, which is strongly related to the increasing pith-bark trend of MFA. The variation of tand along the radius can be partly explained by MFA, and partly by the gradient of extractives due to heartwood formation. The coupling effect of MFA and extractives could be separated through the analysis of log(tand) - log(E'/r) diagram. For the studied species, the extractive content putatively associated to heartwood formation generally tends to decrease the wood damping coefficient. However, this weakening effect of extractives was not observed for inner part of the heartwood, suggesting the mechanical action of extractives was reduced during their chemical ageing.
ISSN: 1435-0211

hal-00797055
https://hal.archives-ouvertes.fr/hal-00797055
https://hal.archives-ouvertes.fr/hal-00797055/document
https://hal.archives-ouvertes.fr/hal-00797055/file/Radial_variations_vibrational_Zhang_al.pdf

Éditeur(s) : EDP Sciences
Résumé : Daily growth increments measured in the otolith of Thunnus atlanticus were used to estimate the age and growth of individuals. which were sampled from an artisanal fishery operating around fish aggregating devices (FADs) moored off Martinique Island. In this study, 76 otoliths were analysed for fish ranging from 20 to 68 cm fork lengths (FL). The fish were caught using trolling lines at depths ranging from 0 to 10 m. Counts were made, under a light microscope, on the external part of the transverse section of the sagittae, from the primordium to the ventral edge. The mean coefficient of variation of the age reading was 2.4%. To validate readings, the number of increments for 11 individuals was counted using both optic and scanning electron microscopes. The calculated relationship between readings of both methods was found to be linear, with a slope of 1.03 and R-2 = 0.99. Frequency of growth increment formation could not be validated. Growth rates derived from otolith readings were, however, compared to those obtained using a modal progression analysis, which was performed on the length-frequency distributions of the landings over a period of two months. The corroboration between the growth rates was good. One increment was assumed to represent one day. The parameters of the von Bertalanffy growth curve for both sexes were L-infinity = 71.4 cm FL, k = 0.002 day(-1) and tau(0) = -80 days. According to our results, there is no evidence that Martinican moored FADs act as ecological traps for blackfin tuna. Instead, young blackfin tuna probably leave the vicinity of Martinican moored FADs to undergo a trophic migration at 7 to 8 month-old, and then come back about 8 months later to breed in the Lesser Antilles area.
Les microstructures présentes dans les otolithes de Thunnus atlanticus ont été utilisées pour estimer l'âge et la croissance des thons capturés par la pêcherie artisanale exploitant les dispositifs de concentrations de poissons (DCP) mouillés autour de la Martinique. Des thons de 20 à 68 cm de longueur à la fourche (LF) ont été capturés à la ligne de traîne de surface entre 0 et 10 m de profondeur. Les stries d'accroissement ont été comptées sur 76 otolithes en microscopie optique sur la partie externe des coupes transversales de la sagitta, du nucléus jusqu'à l'extrémité verticale de la coupe (coefficient de variations 2,4 %). Afin de vérifier qu'il n'y avait pas de sous-estimation du nombre de stries, nous avons effectué un comptage, en microscopie électronique à balayage, pour 11 individus. La relation établie entre ces deux méthodes de comptage est linéaire avec un pente égale à 1,03 et R2 = 0,99. La vitesse de croissance issue de l'analyse des otolithes a été comparée à celle estimée à partir de l'analyse en progression modale des distributions en fréquence de taille des débarquements sur une période de 2 mois. La corroboration entre les deux méthodes était bonne. Nous avons supposé que la formation des stries de croissance suivait un rythme journalier. Les paramètres de l'équation de croissance de von Bertalanffy pour les 2 sexes confondus sont: L-infinity = 71.4 cm FL, k = 0.002 day(-1) and tau(0) = -80 days. Les résultats de cette étude n'indiquent pas que les DCP ancrés martiniquais puissent agir comme des pièges écologiques pour les thons noirs. Les jeunes thons noirs semblent au contraire quitter la proximité des DCP et entreprendre une migration trophique lorsqu'ils atteignent 7 à 8 mois. Ils ne reviendraient ensuite dans la zone des Petites Antilles qu'environ 8 mois plus tard, manifestement pour se reproduire.
Aquatic Living Resources (0990-7440) (EDP Sciences), 2004 , Vol. 17 , N. 1 , P. 13-18

Droits : EDP Sciences, IFREMER, IRD 2004
http://archimer.ifremer.fr/doc/2004/publication-396.pdf
DOI:10.1051/alr:2004009
http://archimer.ifremer.fr/doc/00000/396/

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
The anisotropy of vibrational properties influences the acoustic behaviour of wooden pieces and their dependence on grain angle (GA). As most pieces of wood include some GA, either for technological reasons or due to grain deviations inside trunks, predicting its repercussions would be useful. This paper aims at evaluating the variability in the anisotropy of wood vibrational properties and analysing resulting trends as a function of orientation. GA dependence is described by a model based on transformation formulas applied to complex compliances, and literature data on anisotropic vibrational properties are reviewed. Ranges of variability, as well as representative sets of viscoelastic anisotropic parameters, are defined for mean hardwoods and softwoods and for contrasted wood types. GA-dependence calculations are in close agreement with published experimental results and allow comparing the sensitivity of different woods to GA. Calculated trends in damping coefficient (tanδ) and in specific modulus of elasticity (E′/ρ) allow reconstructing the general tanδ-E′/ρ statistical relationships previously reported. Trends for woods with different mechanical parameters merge into a single curve if anisotropic ratios (both elastic and of damping) are correlated between them, and with axial properties, as is indicated by the collected data. On the other hand, varying damping coefficient independently results in parallel curves, which coincide with observations on chemically modified woods, either "artificially", or by natural extractives.
ISSN: 0043-7719

hal-00804242
https://hal.archives-ouvertes.fr/hal-00804242
https://hal.archives-ouvertes.fr/hal-00804242/document
https://hal.archives-ouvertes.fr/hal-00804242/file/Anisotropy_wood_variational_properties_Bremaud_al_2011.pdf
DOI : 10.1007/s00226-010-0393-8