1,721,148 research outputs found
Structure and functioning of riparian woodland of the milo river (tributary of niger river) Guinea
No full textCe travail de thèse a pour objectif de comprendre le fonctionnement éco-hydrologique de la plaine alluviale du bassin du Milo, haut affluent du Niger en Guinée. La collecte et la synthèse de toutes les données hydro-climatiques disponibles au cours des cinquante dernières années montrent un déficit hydrique dans la zone d'étude depuis les années 1970. L'analyse des ripisylves a été réalisée sur deux sites plus ou moins impactés par l'activité l'anthropique le long de la rivière Milo. L'étude dendrochronologique a montré qu'une dizaine d'espèces peuvent présenter des cernes de croissance. Néanmoins, en raison d'une délimitation des cernes pas toujours évidente, une forte incertitude limite une étude dendro-climatique approfondie. L'analyse isotopique des échantillons d'eaux prélevées a montré une forte variation saisonnière et une bonne connectivité entre la rivière et sa nappe alluviale. L'essai de mesures dendroisotopiques suggère des variations possibles de source d'eau entre saisons et périodes sèches et humides. L'analyse de la biodiversité forestière donne des indices sur la structure et le fonctionnement des ripisylves et sur leur degré et modalité d'atteinte de leur intégrité écologique. Elle montre des différences significatives entre sites et entre unités géomorphologiques composant la plaine alluviale avec une meilleure préservation des fonctionnalités de la ripisylve sur le site de Kérouané moins soumis à la pression anthropique.This thesis aims to understand the eco-hydrological functioning of the alluvial plain from the Milo basin, upper tributary of Niger River in Guinea. The research of all hydro-climatic data available over the last fifty years, and its synthesis, shows a water deficit since the 1970s in this area. The riparian analysis was carried out on two sites more or less impacted by anthropic activities along the river Milo. The dendrochronological study has shown that a dozen of species may display growth rings. Nevertheless, due to bad tree rings limit definition, a high uncertainty remain to assess a correct tree dating, which limits any dendro-climatic studies. The isotopic analysis of the water samples showed a strong seasonal variation and a good connectivity between the river and its alluvial ground water. The trial of dendro-isotopic measurements suggests possible water sources change between seasons, and also between dry and wet periods. The analysis of the forest biodiversity gives indications on the structure and functioning of riparian forests, and on the corresponding ecological integrity's degree and modality. It shows significant differences between sites and between geomorphological units of the alluvial plain. There is a better protection of the riparian features along the Kérouané site, which is less subject to anthropic pressure
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Biogeomorphologic succession dynamics in a Mediterranean river system
Get PDFBiogeomorphologic succession (i.e. reciprocal adjustments between vegetation and geomorphologic dynamics) of the Mediterranean River Tech, France, was analysed using aerial photographs over a period of sixty years between 1942 and 2000. A spatial analysis of the biogeomorphologic succession was undertaken considering effects of flood regime. Interactions between vegetation dynamics and flood events largely controlled the spontaneous replacement of the dense riparian forest removed in October 1940 during an exceptional high magnitude flood event with a recurrence time !100 yr. In response to this major disturbance event, the fluvial landscape demonstrated a very high resilience emphasizing the existence of a positive feedback driven by pioneer riparian vegetation. The observed feedback corresponded to landform accretion, vegetation succession and to an increase of biogeomorphologic stability under current hydrogeomorphologic and bioclimatic conditions. The evolution of the biogeomorphologic system toward stabilisation appeared to be non-linear with a threshold occurring thirty years after the exceptional destructive flood event. This threshold materialized a reinforcement of biogeomorphologic cohesive forces driven by vegetation dynamics. This study showed the control of riparian vegetation on the dynamics of Mediterranean fluvial landscapes and pointed to the need to improve our knowledge about biogeomorphologic succession cycles and threshold dynamics within different biogeomorphologic settings
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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