Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
While vertical motion induced by long-term geological loads is often used to estimate the flexural rigidity of the lithosphere, we intend to evaluate the shear rigidity of the lithosphere using horizontal motion. Our approach considers that the rigidity of the lithosphere may be defined as its resistance to horizontal tectonic lateral forces. In this case, a spatial distribution of an effective shear rigidity can be estimated from the analysis of the interseismic velocity fields. We consider the Western United States zone where weakly strained areas (e.g., the Sierra Nevada) are connected with areas of large strain rate (e.g. San Andreas Fault system). By inverting interseismic strain distribution measured by geodetic methods, we infer the effective shear rigidity of the lithosphere. The forward problem is defined using the equations of linear elasticity. The inversion relies on the minimization of the sum of a quadratic measure of the differences between measured and modelled velocity fields. The functional also includes regularization terms for the parameters of the model. The gradient of the functional with respect to the minimization parameters is computed using an adjoint formulation. This permits the treatment of large dimensional minimization problems. Finally, a measure of the uncertainty of our inversion is illustrated through the covariance matrix of the parameters at the optimum. The optimization chart is validated on two synthetic velocity distributions. Then, the effective shear rigidity variations of the Western United States are estimated using the CMM3 interseismic velocities. The inversion displays low effective rigidities along the San Andreas Fault system, the Mojave Desert and in the Eastern California Shear Zone, while rigid areas are found in the Sierra Nevada and in the South Basin and Range. Finally, we discuss the differences between our strain rate and rigidity maps with previously published results for the Western United States.
ISSN: 0040-1951

Droits : http://hal.archives-ouvertes.fr/licences/copyright/
hal-01505024
https://hal.archives-ouvertes.fr/hal-01505024
https://hal.archives-ouvertes.fr/hal-01505024/document
https://hal.archives-ouvertes.fr/hal-01505024/file/Paper_tectophysics.pdf
DOI : 10.1016/j.tecto.2017.03.015

Éditeur(s) : HAL CCSD IOP Publishing
Résumé : The use of electron probe microanalysis (EPMA) at low voltage allows improvements in the lateral resolution and surface sensitivity of the technique down to the sub-micrometre scale, and it is also useful in minimizing X-ray absorption (for the analysis of ultra-light elements), charging effects and secondary fluorescence. However, EPMA at low voltage is accompanied by a number of problems which may affect the accuracy of quantitative results. A large number of these problems arise from the need of using low-energy X-ray lines such as L- and M-lines, which have low fluorescence yields, large uncertainties in the mass attenuation coefficients, and are affected by several spectroscopic difficulties (e.g., peak shifts and overlaps). Other factors that play an important role at low voltage are carbon contamination, surface oxidation, the quality of sample polishing, the influence of a conductive coating and the limitations of matrix correction procedures. In this paper, we illustrate the capabilities of EPMA at low voltage and we examine in detail the different sources of uncertainty that may affect the accuracy of quantitative results.
ISSN: 1757-8981

hal-00767564
https://hal.archives-ouvertes.fr/hal-00767564
DOI : 10.1088/1757-899X/32/1/012016

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
Probabilistic seismic hazard analyses (PSHA) are commonly based on frequency magnitude statistics from 50-100 yearlong earthquake catalogs, assuming that these statistics are representative of the longer-term frequency of large earthquakes. We test an alternative PSHA approach in continental western Canada, including adjacent areas of northwestern U. S. A., using regional strain rates derived from 179 Global Positioning System (GPS) horizontal velocities. GPS strain rates are converted to earthquake statistics, seismic moment rates, and ground shaking probabilities in seismic source zones using a logic-tree method for uncertainty propagation. Median GPS-based moment rates and shaking estimates agree well with those derived from earthquake catalogs in only two zones (Puget Sound and mid-Vancouver Island). In most other zones, median GPS-based moment rates are 6-150 times larger than those derived from earthquake catalogs (shaking estimates 2-5 times larger), although the GPS-based and catalog estimates commonly agree within their 67% uncertainties. This discrepancy may represent an under-sampling of long-term moment rates and shaking by earthquake catalogs in some zones; however a systematic under-sampling is unlikely over our entire study area. Although not demonstrated with a high confidence level, long-term regional aseismic deformation may account for a significant part of the GPS/catalog discrepancy and, in some areas, represent as much as 90% of the total deformation budget. In order to integrate GPS strain rates in PSHA models, seismic versus aseismic partitioning of long-term deformation needs to be quantified and understood in terms of the underlying mechanical processes.
ISSN: 0148-0227

hal-00689004
https://hal.archives-ouvertes.fr/hal-00689004
DOI : 10.1029/2011JB008213

Éditeur(s) : Elsevier
Résumé : Overexploitation of marine resources remains a problem worldwide. Many works advocate for the use of marine reserves as a central element of future stock management in a sustainable perspective. In the present paper, we address the influence of protected areas upon fisheries sustainability within an eco-systemic framework through a dynamic bio-economic model integrating a trophic web, catches and environmental uncertainties. The model is spatially implicit. The evaluation of the ecosystem is designed through the respect along time of constraints of both conservation and guaranteed captures. Using the mathematical concept of invariance kernel in a stochastic context, we define different MPA effects according to biodiversity catches or mixed points of view. Numerical simulations inspired from data of Abore coral reef reserve in New Caledonia illustrate the main concepts. In this case, it is pointed out how MPA conservation effect is not necessarily conflicting with MPA catches effect. it is shown that such a co-viability requires medium exploitation rate. Moreover, the climatic changes represented by rise in cyclonic events seem to reinforce these assertions. (C) 2007 Elsevier B.V. All rights reserved.
Ecological Modelling (0304-3800) (Elsevier), 2007-11 , Vol. 208 , N. 2-4 , P. 353-366

Droits : 2007 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/2007/publication-3510.pdf
DOI:10.1016/j.ecolmodel.2007.06.018
http://archimer.ifremer.fr/doc/00000/3510/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
A new portable sampling system was developed to extract Radium isotopes from large volumes (up to 300 L) of fresh surface- and ground-waters of low Ra-activities (<5 mBq/L). Ra is quantitatively adsorbed on a small amount (6.5 g) of MnO2-coated acrylic fibers, which are then dried and burned at 600 °C in the laboratory. The resulting Mn-oxide powder (about 2 cm3 when compacted) is then analyzed through gamma-ray spectrometry which allows measurement of the whole Ra quartet (226Ra, 228Ra, 224Ra and 223Ra) in a single counting of a few days. The usual relative standard combined uncertainties (1σ) are 2–3% for 226Ra, 228Ra and 224Ra; and less than 10% for 223Ra. This method was applied to the analysis of Ra in karstic waters of the Lez aquifer, and surface- and ground-waters of the upper and middle Vidourle watershed (South of France). The analyzed waters have relatively low 226Ra activities (1–4 mBq/L) in both cases, regardless of the contrasted geology (Mesozoic limestone vs crystalline Variscan basement), but clearly distinct (228Ra/226Ra) ratios in agreement with the differences in Th/U ratios of the two drained areas. Short-lived Ra isotopes (224Ra and 223Ra) appear to be mainly influenced by near-surface desorption/recoil processes for most of the sampling sites.
ISSN: 0969-8043

hal-01491281
https://hal.archives-ouvertes.fr/hal-01491281
DOI : 10.1016/j.apradiso.2016.12.010

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
The natural river water certified reference material SLRS-5 (NRC-CNRC) was routinely analysed in this study for major and trace elements by ten French laboratories. Most of the measurements were made using ICP-MS. Because no certified values are assigned by NRC-CNRC for silicon and 35 trace element concentrations (rare earth elements, Ag, B, Bi, Cs, Ga, Ge, Li, Nb, P, Rb, Rh, Re, S, Sc, Sn, Th, Ti, Tl, W, Y and Zr), or for isotopic ratios, we provide a compilation of the concentrations and related uncertainties obtained by the participating laboratories. Strontium isotopic ratios are also given. Le matériau de référence certifié d'eau de rivière naturelle SLRS-5 (NRC-CNRC) est analysé régulièrement comme contrôle qualité par dix laboratoires français étudiant les éléments majeurs et en trace dans les solutions naturelles. La plupart des mesures sont réalisées par ICP-MS. Le silicium et 35 éléments en trace (terres rares, Ag, B, Bi, Cs, Ga, Ge, Li, Nb, P, Rb, Rh, Re, S, Sc, Sn, Th, Ti, Tl, W, Y et Zr) ne sont pas certifiés par NRC-CNRC. Aucun rapport isotopique n'est disponible. Nous proposons, pour ces éléments, des valeurs moyennes et leurs incertitudes associées obtenues par les différents laboratoires participants. Le rapport isotopique de Sr est aussi mesuré.
ISSN: 1639-4488

hal-00906166
https://hal.archives-ouvertes.fr/hal-00906166
DOI : 10.1111/j.1751-908X.2013.00232.x

Résumé : After 12 years of a difficult start, the sea bass (Dicentrarchus labrax) breeding projects are multiplying. Faced with the constraints presented by the sites used in the past, farming at sea seems to offer conditions more conducive to the growth and survival of the animals. The zootechnical data from the farm makes it possible to link the rate of growth and the thermal profile of the site. Risks and uncertainties still weigh heavily on aquafarming projects, but solutions such as insurance are helping to improve their economic feasibility. The economic and financial analysis comes up with good overall profitability of the project, even if the duration of the breeding cycle and the necessity to ensure a progressive increase in operating capacity make the start-up phase long and not very lucrative.
(OCR non controlé) Après 12 années d'un démarrage difficile, les projets d'élevage du loup (Dicentrarchus labrax) se multiplient. Face aux contraintes que présentent les sites utilisés par le passé, l'élevage en mer semble offrir des conditions plus favorables à la croissance et à la survie des animaux. Les données zootechniques de l'élevage permettent de mettre en relation la vitesse de croissance et le profil thermique du site. Risques et incertitudes pèsent encore lourdement sur les projets aquacoles, mais des solutions telles que l'assurance contribuent à améliorer leur faisabilité économique. L'analyse économique et financière conclut à une bonne rentabilité globale du projet même si la durée du cycle d'élevage et la nécessité d'assurer une montée en puissance progressive de l'exploitation rendent la phase de démarrage longue et peu rémunératrice.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/1989/rapport-2417.pdf
http://archimer.ifremer.fr/doc/00000/2417/

Éditeur(s) : HAL CCSD Réseau « Développement durable et territoires fragiles »
Résumé : The Green and Blue infrastructure (Trame verte et bleue –TVB) is a new conservation policy tool based on the notions of ecological network and corridor. The introduction of this new instrument through the French Grenelle environment commitments brings about some change in the spatial strategy of the conservation policy. Beyond the identification of priority conservation areas, ecological planning of all the territory is concerned. The TVB’s implementation process establishes the connection of multi and nested decisional and action levels. It thus creates specific situations of complexity and uncertainty that require innovation and perpetual change of governance. The study of the Auvergne region case through the adaptive governance analytical framework highlights the potential fruitful role of Regional nature parks in such dynamics of change and learning. Mots-clés : aménagement durable des territoires, biodiversité, réseau écologique, corridor écologique, gouvernance adaptative, socio-écosystème, trame verte et bleue Keywords : Sustainable landplaning, Biodiversity, Ecological network, Adaptive governance, socio-ecosystem
La Trame verte et bleue (TVB), nouveau dispositif d’action publique visant à enrayer la perte de biodiversité traduit un renouvellement des référentiels de justification des politiques de conservation et de leur stratégie territoriale. Il s’agit d’intégrer la planification écologique dans l’aménagement de l’ensemble du territoire. Le processus de territorialisation de la TVB met en rapport de multiples niveaux de décision et d’action imbriqués. Il crée de ce fait des configurations inédites de complexité et d’incertitude et implique des innovations en termes de gouvernance que le cadre analytique de la gouvernance adaptative permet d’appréhender. En nous appuyant sur l’exemple du Parc Naturel Régional des Volcans d’Auvergne, nous analysons le rôle que ces institutions sont susceptibles de jouer dans ces dynamiques de changement et d’apprentissage socio-technique et politique qui conditionnent une mise en œuvre effective de la TVB.
ISSN: 1772-9971

hal-01195370
https://hal.archives-ouvertes.fr/hal-01195370
DOI : 10.4000/developpementdurable.9675
PRODINRA : 269288

Éditeur(s) : HAL CCSD
Résumé : Tropical forests are a biodiversity hotspot, with the coexistence of numerous species until a fine spatial scale. Particularly, 16.000 tree species coexist in Amazonia, 1.800 in Frenche Guiana and between 120 and more than 200 tree species per hectare. However, there are some uncertainties in maintaining diversity in regard to global changes. Hence before predicting the diversity evolution face of global changes, fundamental studies are needed to understand which assembly processes are involved in the maintenance of diversity. These fundamental studies still relevant given the lack of consensus on the relative importance of assembly processes. This thesis is a continuation of these fundamental studies, using innovative integrative approach, at multi-scale, to address three types of diversity: taxonomic diversity, functional and phylogenetic. Our results challenge the importance of environmental filtering for hydrological and chemical properties of soils, versus the importance of biotic interactions on community assembly. Furthermore, our results suggest that species distributions could be affected by forest dynamics related to falling trees and therefore by light availability. Finally, we have highlighted the importance of dispersal limitation on community assembly.
Les forêts tropicales représentent un ‘hotspot’ de diversité avec un nombre considérable d’espèces qui coexistent jusqu’à une échelle locale fine. Plus particulièrement, 16 000 espèces d’arbres coexistent en Amazonie, 1 800 en Guyane française et entre 120 et plus de 200 espèces d’arbres par hectare. Cependant, le maintien de cette diversité face aux changements globaux actuels et à venir (qu’ils soient anthropiques ou climatiques…) est incertain. Avant de pouvoir prédire l’évolution de la diversité face aux changements globaux, un travail fondamental est nécessaire afin de comprendre les processus d’assemblage des communautés, processus qui maintiennent cette diversité. Ce travail est réalisé depuis de nombreuses années en écologie et reste d’actualité vu l’absence de consensus quant à l’importance relative des processus d’assemblage. Cette thèse s’inscrit dans la continuité de ce travail fondamental en utilisant une approche intégrative innovante, qui aborde de manière multi-échelle trois types de diversité : diversité taxonomique, fonctionnelle et phylogénétique. Nos résultats questionnent sur l'importance du filtrage environnemental quant aux propriétés hydrologiques et chimiques des sols, et sur celle des interactions biotiques dans l’assemblage de la communauté étudiée. Par ailleurs, nos résultats suggèrent que les distributions d’espèces puissent être influencées par la dynamique forestière en lien avec les chutes d’arbres et donc avec la disponibilité en lumière. Enfin, nous avons mis en évidence l’importance de la limitation de dispersion.
https://tel.archives-ouvertes.fr/tel-01418447

NNT : 2016YANE0003
tel-01418447
https://tel.archives-ouvertes.fr/tel-01418447
https://tel.archives-ouvertes.fr/tel-01418447/document
https://tel.archives-ouvertes.fr/tel-01418447/file/these.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Imaging deep active volcanic areas remains a challenge in our understanding of their activity and evolution, especially in subduction zones. Study of magnetic anomalies is appropriate to access such dynamics in depth. The magnetic anomaly pattern of the Lesser Antilles Arc (LAA) subduction is studied through Curie Point Depth (CPD), interpreted as the depth of the 580 °C isotherm, and developed to better assess the deep thermal structure of the arc. The depth of the estimated CPD exhibits a complex topography. Keeping in mind the overall uncertainty associated with this method, a main doming is evidenced below the Guadeloupe archipelago. Its apex is shifted towards the ancient arc, suggesting a very hot state of the fore-arc/arc domain. To better understand the LAA thermal state, we perform 2D thermo-mechanical simulations of the subduction zone. Recalling that magnetite is a serpentinization by-product, we simulate water transfer triggered by slab dehydration to test the assumption of fore-arc serpentinization suggested by the positive magnetic anomaly in the vicinity of the Guadeloupe archipelago. In this area, the subduction-induced arc lithosphere hydration and related weakening trigger a fast heating of the upper plate by basal convective removal. This process of fast arc lithosphere thinning may apply where simultaneously the volcanic arc is split in two and normal convergence is high enough. As serpentinization strongly decreases P-wave velocity, we propose a new interpretation of a published seismic profile below Guadeloupe. The seismic layer previously interpreted as the arc lower crust may rather be a layer of serpentinized mantle, as supported by spatial correlations between gravimetric and magnetic anomalies. Consequently, at the scale of Guadeloupe Island, the fore-arc Moho would be shallower than initially assumed, with a dome shape more consistent with both the extensive deformation active since the Oligocene in the inner fore-arc and the CPD doming.
ISSN: 0040-1951

Droits : http://creativecommons.org/licenses/by-nc-nd/
insu-01505300
https://hal-insu.archives-ouvertes.fr/insu-01505300
https://hal-insu.archives-ouvertes.fr/insu-01505300/document
https://hal-insu.archives-ouvertes.fr/insu-01505300/file/Gailler-2017.pdf
DOI : 10.1016/j.tecto.2017.03.014

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-01526430
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01526430
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01526430/file/Dermal%20absorption%20of%20semivolatile%20organic%20compounds_accepted.pdf
DOI : 10.1016/j.envint.2017.02.005
PUBMED : 28249739

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
An inter-laboratory exercise was organized under the PHARMAS EU project, by the Advanced School of Public Health (EHESP), in order to evaluate the performances of analytical methods for the measurement of antibiotics in waters (surface and tap). This is the first time such an exercise on antibiotics has been organized in Europe, using different kinds of analytical methods and devices. In this exercise thirteen laboratories from five countries (Canada, France, Italy, the Netherlands and Portugal) participated, and a total number of 78 samples were distributed. During the exercise, 2 testing samples (3 bottles of each) prepared from tap water and river water, respectively, spiked with antibiotics, were sent to participants and analyzed over a period of one month. A final number of 77 (98.7%) testing samples were considered. Depending on substances studied by each participant, 305 values in duplicate were collected, with the results for each sample being expressed as the target concentration. A statistical study was initiated using 611 results. The mean value, standard deviation, coefficient of variation, standard uncertainty of the mean, median, the minimum and maximum values of each series as well as the 95% confidence interval were obtained from each participant laboratory. In this exercise, 36 results (6% of accounted values) were outliers according to the distribution over the median (box plot). The outlier results were excluded. In order to establish the stability of testing samples in the course of the exercise, differences between variances obtained for every type of sample at different intervals were evaluated. The results showed no representative variations and it can be considered that all samples were stable during the exercise. The goals of this inter-laboratory study were to assess results variability when analysis is conducted by different laboratories, to evaluate the influence of different matrix samples, and to determine the rate at which participating laboratories successfully completed the tests initiated.
Talanta

hal-00878118
https://hal.archives-ouvertes.fr/hal-00878118
DOI : 10.1016/j.talanta.2012.06.064
PUBMED : 22939142

Éditeur(s) : Pêche thonière et dispositifs de concentration de poissons, Caribbean-Martinique, 15-19 Oct 1999
Résumé : This paper develops a comparative overview of the development of Fish Aggregating Devices (or fads) by the tropical purse seine fisheries in various ocean areas (Atlantic, Indian, Western and Eastern Pacific Oceans). First, a comparative review of fishery statistics is developed. Recent catches on fads by purse seiners can be estimated at a level of one million tons yearly. This comparison allows to describe the fishing zones and catch trends over time, the species composition and size taken in the various fad fisheries. Skipjack tuna is the dominant species in most fad fisheries, but significant amounts of yellowfin and bigeye are also frequently taken under fads. The paper also presents an overview of various observer data concerning the by-catches of the various fisheries using fads. This comparison allows to estimate the total worldwide yearly by-catches at about 100,000 t, and their species composition in each ocean. The fad technology used in the various oceans by purse seiners is described. The recent use of fads by purse seiners has introduced major uncertainties in most stock assessments, because analyses are hampered by changes in the fishing effort in a fad fishery, by changes in fishing zones and in sizes caught. As a last point, the management of fads presently done or in view by the various tuna bodies are introduced. It appears that the present massive use of fads worldwide is perhaps an unsafe fishing mode, which could produce serious overfishing of many stocks. There is then a consensus that the use of fads needs to be controlled and limited to sustainable biological levels.

Droits : Ifremer
http://archimer.ifremer.fr/doc/00042/15278/12664.pdf
http://archimer.ifremer.fr/doc/00042/15278/

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
A calibration method aimed at converting X-ray intensities into absolute units has been tested in different electron microprobes. The calibration requires measurement of the X-ray peak profile and measurement and calculation of the bremsstrahlung intensity emitted from a reference sample, at the energy of the X-ray line of interest. Specifically, measurements of the U M alpha and M beta lines emitted from UO2 and bremsstrahlung intensities emitted from an Al reference sample have been performed on five different instruments. The aim of the work is to determine to what accuracy X-ray intensities emitted from reference samples of actinide elements are transferable among different electron microprobes (virtual standard). The influence of the focussing geometry and different crystals and proportional counters used is analysed. Strategies to reduce the uncertainties affecting the absolute calibration of the studied lines are discussed.
ISSN: 0026-3672

hal-00411437
https://hal.archives-ouvertes.fr/hal-00411437
DOI : 10.1007/s00604-007-0856-2

Éditeur(s) : HAL CCSD European Geosciences Union
Résumé : International audience
The Mediterranean hydrometeorological observatory Cévennes-Vivarais (OHM-CV) coordinates hydrometeorological observations (radars, rain gauges, water level stations) on a regional scale in southeastern France. In the framework of OHM-CV, temporary GPS measurements have been carried out for 2 months in autumn 2002, when the heaviest rainfall are expected. These measurements increase the spatial density of the existing permanent GPS network, by adding three more receivers between the Mediterranean coast and the Cévennes-Vivarais range to monitor maritime source of water vapour flow feeding the precipitating systems over the Cévennes-Vivarais region. In addition, a local network of 18 receivers covered an area of 30 by 30 km within the field of view of the meteorological radar. These regional and local networks of permanent and temporary stations are used to monitor the precipitable water vapour (PWV) with high temporal resolution (15 min). Also, the dense local network provided data which have been inverted using tomographic techniques to obtain the 3-D field of tropospheric water vapour content. This study presents methodological tests for retrieving GPS tropospheric observations from dense networks, with the aim of assessing the uncertainties of GPS retrievals. Using optimal tropospheric GPS retrieval methods, high resolution measurements of PWV on a local scale (a few kilometres) are discussed for rain events. Finally, the results of 3-D fields of water vapour densities from GPS tomography are analysed with respect to precipitation fields derived from a meteorological radar, showing a good correlation between precipitation and water vapour depletion areas.
ISSN: 1867-1381

hal-01022833
https://hal.archives-ouvertes.fr/hal-01022833
https://hal.archives-ouvertes.fr/hal-01022833/document
https://hal.archives-ouvertes.fr/hal-01022833/file/amt-7-553-2014.pdf
DOI : 10.5194/amt-7-553-2014

Éditeur(s) : HAL CCSD Wiley
Résumé : The intensification of the hydrological cycle, with an observed and modeled increase in drought incidence and severity, underscores the need to quantify drought effects on carbon cycling and the terrestrial sink. FLUXNET, a global network of eddy covariance towers, provides dense data streams of meteorological data, and through flux partitioning and gap filling algorithms, estimates of net ecosystem productivity (FNEP), gross ecosystem productivity (P), and ecosystem respiration (R). We analyzed the functional relationship of these three carbon fluxes relative to evaporative fraction (EF), an index of drought and site water status, using monthly data records from 238 micrometeorological tower sites distributed globally across 11 biomes. The analysis was based on relative anomalies of both EF and carbon fluxes and focused on drought episodes by biome and climatic season. Globally P was ≈50% more sensitive to a drought event than R. Network-wide drought-induced decreases in carbon flux averaged −16.6 and −9.3 g C m−2 month−1 for P and R, i.e., drought events induced a net decline in the terrestrial sink. However, in evergreen forests and wetlands drought was coincident with an increase in P or R during parts of the growing season. The most robust relationships between carbon flux and EF occurred during climatic spring for FNEP and in climatic summer for P and R. Upscaling flux sensitivities to a global map showed that spatial patterns for all three carbon fluxes were linked to the distribution of croplands. Agricultural areas exhibited the highest sensitivity whereas the tropical region had minimal sensitivity to drought. Combining gridded flux sensitivities with their uncertainties and the spatial grid of FLUXNET revealed that a more robust quantification of carbon flux response to drought requires additional towers in all biomes of Africa and Asia as well as in the cropland, shrubland, savannah, and wetland biomes globally.
ISSN: 1354-1013

hal-01032076
https://hal.archives-ouvertes.fr/hal-01032076
DOI : 10.1111/j.1365-2486.2009.01991.x

Éditeur(s) : HAL CCSD Elsevier
Résumé : Analyses of tree diversity and community composition in tropical rain forests are usually based either on general herbarium data or on a restricted number of botanical plots. Despite their high taxonomic accuracy, both types of data are difficult to extrapolate to landscape scales. Meanwhile, forestry surveys provide quantitative occurrence data on large areas, and are thus increasingly used for landscape-scale analyses of tree diversity. However, the reliability of these approaches has been challenged because of the ambiguity of the common (vernacular) names used by foresters and the complexity of tree taxonomy in those hyper-diverse communities.We developed and tested a novel approach to evaluate taxonomic reliability of forestry surveys and to propagate the resulting uncertainty in the estimates of several diversity indicators (alpha and beta entropy, Fisher-alpha and Sørensen similarity). Our approach is based on Monte-Carlo processes that simulate communities by taking into account the expected accuracy and reliability of common names. We tested this method in French Guiana, on 9 one-hectare plots (4279 trees – DBH ⩾ 10 cm) for which both common names and standardized taxonomic determinations were available. We then applied our method of community simulation on large forestry inventories (560 ha) at the landscape scale and compared the diversity indices obtained for 10 sites with those computed from precise botanical determination situated at the same localities.We found that taxonomic reliability of forestry inventories varied from 22% (species level) to 83% (family level) in this Amazonian region. Indices computed directly with raw forestry data resulted in incorrect values, except for Gini–Simpson beta-diversity. On the contrary, our correction method provides more accurate diversity estimates, highly correlated with botanical measurements, for almost all diversity indices at both regional and local scales. We obtained a robust ranking of sites consistent with those shown by botanical inventories.These results show that (i) forestry inventories represent a significant part of taxonomic information, (ii) the relative diversity of regional sites can be successfully ranked using forestry inventory data using our method and (iii) forestry inventories can valuably contribute to the detection of large-scale diversity patterns when biases are well-controlled and corrected.The tools we developed as R-functions are available in supplementary material and can be adapted with local parameters to be used for forest management and conservation issues in other regional contexts
ISSN: 0378-1127

hal-01204219
https://hal.archives-ouvertes.fr/hal-01204219
DOI : 10.1016/j.foreco.2014.05.045
PRODINRA : 286554

Éditeur(s) : HAL CCSD AGU and the Geochemical Society
Résumé : International audience
Analysis of short-term deformation along the southern part of Dead Sea Fault (DSF) provides a systematic view of kinematics this part of the continental transform. The southern DSF consists of two principal segments: the Wadi Araba and Jordan Valley faults. In addition to other regional continuous GPS data, this study uses new data from 25 survey sites and 4 continuous GPS stations in Jordan for improved near-field observations. Resulting velocities are reported with 1-sigma uncertainties ranging from 0.4-1.0 mm/yr. Application of elastic dislocation models yields estimates of slip rates for Wadi Araba and Jordan Valley faults are 4.9 +/- 0.4 mm/yr and 4.7 +/- 0.4 mm/yr, respectively. Modeling also suggests different depths of effective fault locking with 15 +/- 5 km and 8 +/- 5 km for the Wadi Araba and Jordan Valley faults, respectively. These slip rates are generally consistent with the upper end of the range of slip rates estimated from late Quaternary geology. Spatial variations in effective fault locking generally correspond with a heterogeneous mantle lithosphere. A similar observation can be observed along the southern San Andreas Fault, and this may reflect the influence of heterogeneity in the uppermost mantle on crustal faulting processes.
ISSN: 1525-2027

hal-00689031
https://hal.archives-ouvertes.fr/hal-00689031
DOI : 10.1029/2011GC003736

Éditeur(s) : HAL CCSD Wiley
Résumé : [b]Aim[/b][br/] [br/] The phylogeographical history of Neotropical species can be difficult to reconstruct because of superimposed Neogene and Quaternary histories, and because of taxonomic uncertainty. We analysed range-wide genetic diversity in a widespread pioneer tree species, Jacaranda copaia (Aubl.) D. Don, to characterize phylogeographical structure, date the evolutionary relationships among lineages, and evaluate the role of dispersal and vicariance in establishing the present geographical range.[br/] [br/] [br/] [b]Location[/b][br/] [br/] Guiana Shield; central, southern and western Amazon Basin; Chocó region; Central America.[br/] [br/] [br/] [b]Methods[/b][br/] [br/] We analysed nine nuclear simple sequence repeat loci (nuSSR), eight chloroplast SSRs (cpSSR), and two cpDNA intergenic sequences in 341 adult trees. Genetic differentiation at nuSSRs was inferred using Bayesian clustering. Dating of chloroplast lineage divergence was obtained using a range of published mutation rates and Bayesian coalescence analyses. Population divergence dating was performed using an isolation-with-migration model for eight loci (one cp sequence and seven nuSSRs).[br/] [br/] [br/] [b]Results[/b][br/] [br/] Nuclear SSR variation identified three geographically overlapping clusters (nu-1, nu-2, nu-3). Twelve cpDNA haplotypes were clustered into two haplogroups (cp-1, cp-2) with the central Amazon harbouring the highest diversity. Molecular dating analysis suggests that cpDNA haplotype diversification started around the end of the Pliocene (2.61 Ma on average), whereas population divergence was more recent and occurred during the mid-Quaternary (point estimates between 357 and 436 ka).[br/] [br/] [br/] [b]Main conclusions[/b][br/] [br/] The genetic variation of J. copaia in the Neotropics was shaped mainly by Pleistocene events. Chloroplast diversity did not display the expected cis/trans Andean disjunction, indicating recent dispersal. Nuclear variation revealed that separate regions share a recent history, with a centre of diversity in the central Amazon Basin. The geographical pattern of diversity is congruent with the distribution of the two subspecies, J. copaia copaia and J. copaia spectabilis, and evidence of nuSSR admixture between the two taxa supports their classification as subspecies.
ISSN: 0305-0270

hal-01032410
https://hal.archives-ouvertes.fr/hal-01032410
DOI : 10.1111/j.1365-2699.2012.02797.x

Résumé : Qu’est ce qui explique la faiblesse d’un Etat qui s’est engagé depuis plus de vingt ans à rompre avec les pratiques de l’autoritarisme et du néo-patrimonialisme ? Pourquoi les promesses d’une démocratisation réussie, malgré le soutien massif des acteurs de la « société internationale » ont paradoxalement débouché sur la déstabilisation de l’Etat dans un contexte de crises récurrentes ? Ce sont les interrogations principales qui orientent cette recherche qui se donne pour ambition d’étudier les processus par lesquels les élites et les masses haïtiennes s’approprient la démocratie. De ce point de vue, la démocratisation s’analyse comme une ressource politique et institutionnelle revendiquée par ces dernières comme élément probant de leur adhésion à la grammaire démocratique. Dès lors, il s’agit de scruter les routes sinueuses et chaotiques empruntées par la démocratisation en Haïti, en interrogeant les diverses séquences marquantes de l’histoire politique haïtienne. L’accent est mis sur l’importation des technologies institutionnelles d’origine occidentale, notamment durant la période ouverte en 1994 avec la réinstallation de Jean-Bertrand Aristide dans ses fonctions de président et celle qui commence en 2004 avec son départ forcé du pouvoir. Ces deux séquences historiques, sous-tendues par des plans de reconstruction de l’Etat, sont marquées par la mobilisation de ressources diverses, en vue de jeter les bases d’une nouvelle gouvernance politique et économique. Elles circonscrivent également un champ de représentations conflictuelles, caractérisé par la compétition entre les Etats occidentaux et la lutte pour la répartition des enjeux de puissance entre les organisations internationales et les élites locales. L’analyse du processus de démocratisation conduit à des observations paradoxales : l’exacerbation de la violence, l’actualisation de l’autoritarisme, la multiplication des situations déviantes découlant des stratégies des acteurs locaux. Ces derniers tentent d’échapper aux contraintes imposées par des acteurs externes qui interviennent afin de sanctionner, d’arbitrer et d’imposer des décisions aux factions en luttes pour le pouvoir. Ainsi, la démocratisation passe par des crises d’adaptation, des phases contradictoires de recomposition, d’hybridation des institutions importées et parfois de contournement des normes et procédures. Entre les acteurs internes et externes s’établit et s’organise une dynamique interactive qui influence l’Etat dont la configuration finale est loin de correspondre aux objectifs affichés à travers les réformes engagées. Afin de mieux mettre en évidence les traits distinctifs de cet Etat forgé dans l’incertitude et l’imprécision, la thèse propose de restituer les dynamiques et l’historicité propres à la société haïtienne, en privilégiant l’hypothèse de la réinvention de l’Etat. Paradoxalement, l’État peut être le produit de processus de violence et la part chaotique que comporte la situation en Haïti peut recéler les prémices de sa construction.
What does explain the weakness of a State which has committed more than 20 years to break with the practices of authoritarianism and neo-patrimonialism? Why the promises of a successful democratization, despite the massive support of the actors of the “international society” paradoxically led to the destabilization of the State in the context of recurrent crises? These are the key questions guiding this research, whose ambition is to study the processes by which elites and the Haitian masses appropriate democracy. From this point of view, democratization is analyzed as a political and institutional resource claimed by them as convincing evidence of their adherence to democratic grammar. Therefore, it is scrutinizing the winding roads and chaotic way borrowed by democratization in Haiti, by querying various striking sequences of Haitian political history. Emphasis is placed on the importation of institutional technologies of Western origin, particularly during the period opened in 1994 with the resettlement of Jean-Bertrand Aristide in his duties as president and on the period which starts in 2004 with his forced departure from power. These two historical sequences, underpinned by plans for the reconstruction of the State, are marked by the mobilization of various resources, with a view to laying the foundations for new political and economic governance. They also define a field of conflicting representations, characterized by competition between Western States and the struggle for the distribution of power between the international organizations and local elites issues.The analysis of the process of democratization leads to paradoxical representations: the exacerbation of violence, the updating of authoritarianism, the multiplication of deviant situations arising from the strategies of local actors. The latter are trying to escape from the constraints imposed by external actors involved in order to punish, to arbitrate and to impose decisions on the factions struggling for power. Thus, democratization goes hand in hand with crises of adaptation, contradictory phases of re-composition, hybridization of the imported institutions and, sometimes with circumvention of the standards and procedures. Between internal and external actors are settled and organized interactive dynamics that influence the State of which the final configuration is far short of the objectives set out through the aimed reforms. In order to better highlight the distinguishing features of this State forged in uncertainty and vagueness, the thesis proposes to analyze the dynamics and historicity of Haitian society, privileging, the hypothesis of the reinvention of the State. Paradoxically, the State may be the product of process of violence and the chaotic part that includes the situation in Haiti can conceal the beginning of its construction.

http://www.theses.fr/2014AGUY0849/document