50184 research outputs found

    La fabrique européenne des politiques de réconciliation - Introduction

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    International audienceCette introduction présente l'état de l'art sur les médiations européennes dans la gestion des sorties de conflit, et en propose une approche sociologique à la charnière entre sociologie de l'international et problématique de l'européanisatio

    A labour-based approach to the analysis of structural transformation: application to French agricultural holdings 2000

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    Ce rapport est disponible chez : UMR MOISA, 1The question of farm size has long been a concern in the agricultural economics literature. The observation of a long-lasting persistence of so-called small farms drew the attention of numerous researchers. The size of farms is often approximated by the farm area in hectares or the added value and gross margin. We propose to investigate the opportunity to use labour (family labour and hired, permanent and seasonal, wage labour) as an entry point for a typology of agricultural holdings, with an application on French data from the Census collected in 2000. Then, we characterize the holdings belonging to the groups defined by the typology based on the type of labour.La question de la taille des exploitations agricoles, en relation avec leurs performances, a été largement abordée par la littérature dédiée à l’économie agricole. En particulier, la persistance de l’existence de petites exploitations a attiré l’attention. La taille des exploitations est le plus souvent estimée en hectares, en valeur ajoutée ou en chiffre d’affaires. Cet article propose une entrée par le travail (familial ou salarié, saisonnier ou permanent) pour construire une typologie des exploitations françaises sur la base du Recensement Agricole 2000. Il caractérise ensuite les différents types d’exploitations identifiées

    Vegetation patch effects on flow resistance at channel scale

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    International audienceThanks to a specific experimental design in a controlled channel, this paper aimed at quantifying how patches of four different ditches plant species affect integrated flow resistance parameters, the Manning coefficient. These plants, frequently encountered in the farmland ditches and irrigation channels of the south of France, were selected according to a large range of hydrophilic requirements, flexibility and branching complexity related to the plant blockage factor. Eight different spatial patches (regular, random, lateral or central patches) of each plant with crescent or similar plant densities were implanted at the bottom of a controlled channel where the water levels and water velocities were measured for three different discharges in steady and unsteady flow conditions. Resistance parameters (Manning parameters) were then estimated from the total head-loss, or from flow propagation velocity in the channel thanks to inversion of an hydrodynamic model. These experiments allow us to test the significance effect of channel vegetation patches and densities on flow resistance parameters at the reach scale

    InfraPhenoGrid: A scientific workflow infrastructure for Plant Phenomics on the Grid

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    International audiencePlant phenotyping consists in the observation of physical and biochemical traits of plant genotypes in response to environmental conditions. Challenges , in particular in context of climate change and food security, are numerous. High-throughput platforms have been introduced to observe the dynamic growth of a large number of plants in different environmental conditions. Instead of considering a few genotypes at a time (as it is the case when phenomic traits are measured manually), such platforms make it possible to use completely new kinds of approaches. However, the data sets produced by such widely instrumented platforms are huge, constantly augmenting and produced by increasingly complex experiments, reaching a point where distributed computation is mandatory to extract knowledge from data. In this paper, we introduce InfraPhenoGrid, the infrastructure we designed and deploy to efficiently manage data sets produced by the PhenoArch plant phenomics platform in the context of the French Phenome Project. Our solution consists in deploying scientific workflows on a Grid using a middle-ware to pilot workflow executions. Our approach is user-friendly in the sense that despite the intrinsic complexity of the infrastructure, running scientific workflows and understanding results obtained (using provenance information) is kept as simple as possible for end-users

    Diversity of decay resistance strategies of durable tropical woods species: Bocoa prouacencsis Aublet, Vouacapoua americana Aublet, Inga alba (Sw.) Wild

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    International audienceThe study of decay resistance in wood is of interest for wood end-users but also for the global carbon balance since wood biodegradation is a key driver of forest ecosystem functioning through its impacts on carbon and nutrient cycling. We studied the density and wood extractive contents in order to understand decay resistance against soil microflora after 90 days exposure of sapwood and heartwood from three Neotropical wood species known for their decay resistance: Bocoa prouacensis, Vouacapoua americana, Inga alba. Decay resistance was correlated with density more than wood extractive content. The results highlighted different decay resistance strategies. In B. prouacensis, both sapwood and heartwood were highly resistant due to the high density and high content of antifungal wood extractives. In V. americana heartwood, decay resistance was due to the high synergistic-acting wood extractive content. Conversely, with the least dense wood species I. alba, we found that decay resistance was due to the antifungal wood extractives synthesized early in the sapwood. In conclusion, we showed that the three wood species with the same level of heartwood decay resistance performance had different decay resistance strategies according to the anatomic and defensive wood traits

    Mapping ground subsidence phenomena in Ho Chi Minh City through the radar interferometrytechnique using ALOS PALSAR Data

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    [Departement_IRSTEA]Territoires [TR1_IRSTEA]SYNERGIE [Axe_IRSTEA]TETIS-ATTOSInternational audienceThe rapidly developing urbanization since the last decade of the 20th century has led to extensive groundwater extraction, resulting in subsidence in Ho Chi Minh City, Vietnam. Recent advances in multi-temporal spaceborne SAR interferometry, especially with a persistent scatters interferometry (PSI) approach, has made this a robust remote sensing technique for measuring large-scale ground subsidence with millimetric accuracy. This work has presented an advanced PSI analysis, to provide an unprecedented spatial extent and continuous temporal coverage of the subsidence in Ho Chi Minh City from 2006 to 2010. The study shows that subsidence is most severe in the Holocene silt loam areas along the Sai Gon River and in the southwest of the city. The groundwater extraction resulting from urbanization and urban growth is mainly responsible for the subsidence. Subsidence in turn leads to more flooding and water nuisance. The correlation between the reference leveling velocity and the estimated PSI result is R-2 = 0.88, and the root mean square error is 4.3 (mm/year), confirming their good agreement. From 2006 to 2010, the estimation of the average subsidence rate is -8.0 mm/year, with the maximum value up to -70 mm/year. After four years, in regions along Sai Gon River and in the southwest of the city, the land has sunk up to -12 cm. If not addressed, subsidence leads to the increase of inundation, both in frequency and spatial extent. Finally, regarding climate change, the effects of subsidence should be considered as appreciably greater than those resulting from rising sea level. It is essential to consider these two factors, because the city is inhabited by more than 7.5 million people, where subsidence directly impacts urban structures and infrastructure

    Developing a method to map coconut agrosystems from high-resolution satellite images

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    https://icaci.org/files/documents/ICC_proceedings/ICC2015/papers/38/fullpaper/T38-504_1427765394.pdfInternational audienceOur study aims at developing a generalizable method to exploit high resolution satellite images(VHR) for mapping coconut-based agrosystems, differentiating them from oil palm agrosystems.We compared two methods of land use classification. The first one is similar to that described byTeina (2009), based on spectral analysis and watershed segmentation, which we simplified byusing the NDVI vegetation index. The second one is the semi-automatic classification based ontexture analysis (PAPRI method of Borne, 1990). These methods were tested in two differentenvironments: Vanua Lava (Vanuatu; heterogeneous landscape, very ancient plantations) andIvory Coast (Marc Delorme Research Station, monoculture, regular spacing, oil palm plantations);and their results were evaluated against manually digitized photo-interpretation maps.In both situations, the PAPRI method produced better results than that of Teina (global kappa of0.60 vs. 0.40). Spectral signatures do not allow a sufficiently accurate mapping of coconut and donot differentiate it from oil palm, despite their different NDVI signatures. The PAPRI methoddifferentiates productive coconut from mixed plantations and other vegetation, either high or low(70% accuracy). In both situations, Teina’s method allows counting 65% of the coconut treeswhen they are well spaced. To increase the method accuracy, we suggest (1) field surveys (forsmall scale studies) and/or finer image resolution, allowing a high precision in manual mappingwith a better discrimination between coconut and oil palm, thus limiting the proportion of mixedpixels. (2) A phenological monitoring could improve the distinction between coconut and oil palmagrosystems. (3) Hyper-spectral images should allow extracting more precisely the respectivesignatures of both species. Another possibility would be (4) an object-oriented analysis asproposed by the eCognition software. Finally, (5) coupling the Lidar system with watershedanalysis would allow a better characterization of coconut varietal types

    Modelling the hydrological behaviour of a coffee agroforestry basin in Costa Rica

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    UMR LISAH, Equipe Eau et Polluants en Bassins VersantsThe profitability of hydropower in Costa Rica is affected by soil erosion and sedimentation in dam reservoirs, which are in turn influenced by land use, infiltration and aquifer interactions with surface water. In order to foster the provision and payment for Hydrological Environmental Services (HES), a quantitative assessment of the impact of specific land uses on the functioning of drainage-basins is required. The present paper aims to study the water balance partitioning in a volcanic coffee agroforestry microbasin (1 km(2), steep slopes) in Costa Rica, as a first step towards evaluating sediment or contaminant loads. The main hydrological processes were monitored during one year, using flume, eddy-covariance flux tower, soil water profiles and piezometers. A new Hydro-SVAT lumped model is proposed, that balances SVAT (Soil Vegetation Atmosphere Transfer) and basin-reservoir routines. The purpose of such a coupling was to achieve a trade-off between the expected performance of ecophysiological and hydrological models, which are often employed separately and at different spatial scales, either the plot or the basin. The calibration of the model to perform streamflow yielded a Nash-Sutcliffe (NS) coefficient equal to 0.89 for the year 2009, while the validation of the water balance partitioning was consistent with the independent measurements of actual evapotranspiration (R-2 = 0.79, energy balance closed independently), soil water content (R-2 = 0.35) and water table level (R-2 = 0.84). Eight months of data from 2010 were used to validate modelled streamflow, resulting in a NS = 0.75. An uncertainty analysis showed that the streamflow modelling was precise for nearly every time step, while a sensitivity analysis revealed which parameters mostly affected model precision, depending on the season. It was observed that 64% of the incident rainfall R flowed out of the basin as streamflow and 25% as evapotranspiration, while the remaining 11% is probably explained by deep percolation, measurement errors and/or inter-annual changes in soil and aquifer water stocks. The model indicated an interception loss equal to 4% of R, a surface runoff of 4% and an infiltration component of 92%. The modelled streamflow was constituted by 87% of baseflow originating from the aquifer, 7% of subsurface non-saturated runoff and 6% of surface runoff. Given the low surface runoff observed under the current physical conditions (andisol) and management practices (no tillage, planted trees, bare soil kept by weeding), this agroforestry system on a volcanic soil demonstrated potential to provide valuable HES, such as a reduced superficial displacement- capacity for fertilizers, pesticides and sediments, as well as a streamflow regulation function provided by the highly efficient mechanisms of aquifer recharge and discharge. The proposed combination of experimentation and modelling across ecophysiological and hydrological approaches proved to be useful to account for the behaviour of a given basin, so that it can be applied to compare HES provision for different regions or management alternatives

    Thermodynamic modelling of P availability: the case of intercropping rhizosphere

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    Plants of chickpea and durum wheat were cultivated as sole-­‐crop and intercrop in a rhizobox deviceaccording to a substitutive design. Unplanted soil was used as a control treatment. The soil used was a noncarbonated Luvisol with a neutral pH. Plants were harvested at the chickpea flowering stage. The pH, Pavailability and dissolved Ca were measured in soil as extracted by water and CaCl2 (1 and 10 mM). A set ofthermodynamic models were used (i.e. CD MUSIC; Nica Donnan; ion exchange) to simulate and understandmeasured P availability variations in each treatment

    Modification des traits racinaires le long d’une succession secondaire sur des talus routiers: implications dans la dynamique des communautés et la protection des sols contre l’érosion

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    Les traits fonctionnels des plantes varient au cours des successions secondaires végétales. Alors que certains traits ont été largement étudiés, les variations des traits racinaires au cours des successions restent relativement peu documentées. L’objectif de cette étude vise à mieux comprendre en quoi des variations de traits racinaires le long d’une succession secondaire contribuent à la dynamique de communautés végétales méditerranéennes. Pour cela, quinze communautés végétales, âgées de 0 à 69 ans, ont été repérées sur des talus en bordures de routes, dans le nord Montpelliérain. Sur cette chronoséquence, nous nous intéressons à des traits racinaires morphologiques et architecturaux des espèces dominantes, représentant 70% de l’abondance végétale. Nous faisons l’hypothèse que des traits morphologiques des racines fines (< 2 mm) permettent de mieux comprendre les modifications des stratégies d’acquisition et de conservation des ressources en nutriments et en eau. Des traits architecturaux, tels que la présence d’un pivot, de racines traçantes et/ou adventives, permettent d’étudier le rôle des racines dans l’ancrage et la capacité des espèces à coloniser le milieu en réponse aux contraintes topographiques liées à la pente des talus. Dans cette communication, nous présentons (i) la méthode retenue pour l’étude des traits racinaires morphologiques et architecturaux sur des espèces de formes de croissance diverses (herbacées, buissons, arbres) et (ii) discutons des limites et atouts de ces méthodes. Enfin, nous discutons de l’implication de ces traits racinaires dans la capacité des communautés à limiter l’érosion superficielle des talu


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