Offres documentaires et services aux usagers : développement ou effondrement des sujets ?

Intervention à la 6e journée FORMIST qui s\u27est déroulée le 15 juin 2006 à l\u27ENSSIB. Fabrice Papy explique le fondement et les résultats de ses recherches autour des usages de la documentation par les étudiants

Bibliothèque à l\u27heure du Web 2.0 (La) : amélioration significative du service aux usagers ?

Présentation et programme de la journée d\u27étude "La bibliothèque à l\u27heure du Web 2.0 : amélioration significative du service aux usagers ?", organisée par l\u27Université d\u27Artois et le groupe de recherche "Document numérique & Usages" (Université Paris 8), Arras, 22 mai 2008

Foliar and wood traits covary along a vertical gradient within the crown of long-lived light-demanding species of the Congo Basin semi-deciduous forest

Plant functional traits have shown to be relevant predictors of forest functional responses to climate change. However, the trait-based approach to study plant performances and ecological strategies has mostly been focused on trait comparisons at the interspecific and intraspecific levels. In this study, we analyzed traits variation and association at the individual level. We measured wood and leaf traits at different height locations within the crown of five individuals of Pericopsis data (Harms) Meeuwen (Fabaceae) from the northern tropical forest of the Democratic Republic of the Congo. All traits varied between and within individuals. The between-individual variation was more important for leaf traits (23%-48%) than for wood traits (similar to 10%) where the within-individual variation showed to be more important (33%-39%). The sample location height within the crown was found to be the driving factor of this within-individual variation. In a gradient from the base to the top of the crown, theoretical specific hydraulic conductivity and specific leaf area decreased while the stomatal density increased. We found significant relationships among traits and between wood and leaf traits. However, these relationships varied with the position within the crown. The relationship between vessel size and vessel density was negative at the bottom part of the crown but positive upward. Also, the negative relationship between stomatal density and stomatal size became stronger with increasing height within the crown. Finally, the positive relationship between specific leaf area and theoretical specific hydraulic conductivity became stronger in higher parts of the crown, suggesting that P. data constantly adapts its water use with respect to its water supply, more strongly at the top of the crown where the environment is more extreme and less buffered against environmental fluctuations

Ruissellement agricole : cerner les marges de manoeuvre par une modélisation des pratiques de production

Pour mieux orienter la recherche de solutions techniques qui limitent le ruissellement et l'érosion, les auteurs utilisent des modèles de décision dans les exploitations agricoles. En appréciant les marges de manoeuvre des agriculteurs, on évite de proposer des solutions non réalisables. Dans une région très sensible au ruissellement et à l'érosion, le Pays de Caux (Seine-Maritime, France), après enquête auprès d'agriculteurs, on a modélisé les décisions d'assolement et d'organisation du travail. On teste ainsi s'il est possible de localiser autrement les successions de cultures sur le territoire de l'exploitation, de façon à réduire le ruissellement des zones où il est le plus nocif et s'il est envisageable d'introduire dans l'organisation du travail de nouvelles techniques. Il ressort de l'application de ces modèles qu'il est impossible de reconsidérer la localisation des cultures. En revanche, on peut introduire de nouvelles techniques pendant les périodes de culture et surtout d'interculture, avec un résultat qui reste aléatoire. Les techniques qui n'ont d'autres finalités que de réduire le ruissellement ne sont évidemment pas prioritaires aux yeux de l'agriculteur lorsque leur réalisation entre en concurrence avec les objectifs de production. Plutôt que d'introduire de nouvelles techniques, il faut donc plutôt rechercher des modalités d'intervention qui rendent compatibles maîtrise du ruissellement et élaboration du rendement. / To guide research on methods for reducing erosive surface runoff, while avoiding unfeasible solutions, it was of interest to assess how much leeway farmers have in this regard. The study was conducted in the Caux area (Seine-Maritime, France), which is susceptible to surface runoff and erosion. We investigated the possibility of moving crop rotations around the farm to avoid growing crops most susceptible to runoff at the uphill end. We also assessed the possibility of introducing new options that reduce surface runoff into the farming calendar. These questions were first dealt with in separate fields using a rotation decision model, and then a work-planning decision model was used to assess the farm as a whole. We showed for a stylised case that farmers have not much leeway for rotation-blocks modifications. The work-planning model indicates that it should be possible to introduce an intermediate crop, but only on one-sixth of the overall area. The ultimate solutions should involve cultivation procedures that do not disrupt the farmer's work-planning model, and operational strategies that make runoff control compatible with productive farming. Research to this end is currently under way

Recurrent camouflaged invasions and dispersal of an Asian freshwater gastropod in tropical Africa

Background: Non-indigenous taxa currently represent a large fraction of the species and biomass of freshwater ecosystems. The accumulation of invasive taxa in combination with other stressors in these ecosystems may alter the habitats to which native taxa are adapted, which could elicit evolutionary changes in native populations and their ecological interactions. Assessing ecological and evolutionary consequences of invasions simultaneously may therefore be the most effective approach to study taxa with complex invasion histories. Here we apply such an integrated approach to the cerithioid gastropod Melanoides tuberculata, a model system in invasion biology. Results: Molecular phylogenetics and ancestral range reconstructions allowed us to identify several independent Asian invasions in Lakes Malawi and Tanganyika, the Congo River, Nigeria and Cameroon. Some invasive M. tuberculata populations display much variation in shell morphology, and overlap in morphospace with M. tuberculata populations native to Africa. Experiments confirmed great ecophenotyic plasticity in some invasive populations, which, in combination with the overlap in disparity with native populations, masks invaders and their dispersal through Africa. Finally, the results of geographic modeling indicate that cryptic M. tuberculata invasions occurred primarily in densely populated areas. Conclusions: We reveal the continental nature of invasions of Asian M. tuberculata to Africa. Several of the affected ecosystems have high endemicity in Cerithioidea: Lake Tanganyika has an unparalleled diversity in freshwater cerithioids (> 10 endemic genera) and the Congo Basin and Lake Malawi are home to the two largest endemic species clusters of Melanoides in Africa (similar to 12 and similar to 8 species, respectively). Cerithioids perform ecologically important functions in the benthic ecosystems of African freshwaters, but invaders and ecosystem change pose risks to their native diversity. We draw suggestions for more effective conservation strategies from our integrated approach

Les avecs, solution innovantes pour les femmes chefs de m�nages de Goma, RDC

Dans ce blog, Papi Muzuri nous fait découvrir les AVECs. Ce sont des associations qui permettent aux membres inscrits de pouvoir s’octroyer des crédits et épargner ; tout cela dans le but de développer leurs petits commerces et faire face aux difficultés financières du quotidien (Ex : naissances, deuils, mariages). Il présente les origines, le fonctionnement et l’impact de ces associations à Goma, notamment sur la vie des ménages à faibles revenus dirigés par des femmes. Voyant la popularité et le succès de ces associations, l’auteur recommande de formaliser et d’étendre ces associations à l’échelle de la République Démocratique du Congo