Cartographie automatisée des zones à hauts risques naturels par superposition de données multivariées : exemple de la commune de Seillans (Var)

Mémoire HS n° 15 - Géologie Alpine Risques naturels dans le Sud-est de la France - Colloque Association des Géologues du Sud-est - Avignon, 19 et 20 octobre 1989Dans le cadre d'une étude financée par l'EPR PACA, nous avons développé une méthode de cartographie des zones soumises à des mouvements du sol, à l'aide de moyens infonnatiques. Nous avons appliqué cette méthode à la commune de Seillans afin d'intégrer cette carte des risques dans le plan d'occupation des sols. Parmi les phénomènes naturels qui contraignent l'utilisation du sol, nous n'avons pris en compte que le phénomène glissement de terrain : il n'est en effet pas encore possible par les méthodes employées de mettre en évidence les zones soumises à des phénomènes de dissolution; nous avons également laissé de coté le risque lié à l'instabilité des falaises et des chutes de blocs. Pour réaliser cette cartographie des zones soumises à des mouvements de sol, nous avons retenu trois facteurs: - nature lithologique des terrains affleurant, - pente topographique et sa valeur en pourcentage - hydrologi

Plant dispersal by teal (Anas crecca) in the Camargue: duck guts are more important than their feet

12 páginas, 3 figuras, 4 tablas.1. Migratory waterbirds are major vectors for the dispersal of aquatic plants. However, quantitative field studies of the frequency of transport are scarce, and the relative importance of internal and external transport remains unclear. 2. We quantified and compared the rates of internal and external transport of aquatic plant propagules by teal (Anas crecca) in the Camargue (southern France), inspecting the lower gut contents of birds that had been shot (n = 366) and washing birds that had been live-trapped (n = 68) during the winters of 2006–2007 and 2007–2008. 3. Intact propagules (n = 902) of 21 plant taxa were recorded in the rectum of teal, of which 16 germinated or were shown to be viable. Intact propagules were recorded in the rectum of 20% of teal, with up to 171 propagules per individual bird. Chara oogonia were most abundant (60% of intact propagules), suggesting that small size favours internal transport. Eleocharis palustris, Juncus spp. and Potamogeton pusillus (17, 7 and 6% of intact propagules, respectively) were also very abundant. 4. Intact propagules (n = 12) of 10 plant taxa were found on the outside of live teal, and four of these taxa later germinated. Intact propagules were found on 18% of teal. No teal was found to carry more than one propagule externally. There was no difference in size between propagules transported internally and externally. 5. Teal are major dispersers of plants within the Camargue, despite being highly granivorous. Contrary to widespread assumptions in the literature, endozoochory by ducks appears to be a much more important mode of dispersal for aquatic plants than exozoochory. We found no evidence of changes in the probability of plant propagule dispersal at a landscape scale over the course of the winter, so propagule production and zoochory appear to be decoupled over time in aquatic systems.A.-L. Brochet is funded by a Doctoral grant from Office National de la Chasse et de la Faune Sauvage, with additional funding from a research agreement between ONCFS, the Tour du Valat, Laboratoire de Biométrie et de Biologie Evolutive (UMR 5558 CNRS Université Lyon 1) and the Doñana Biological Station (CSIC). This work also received funding from the Agence Nationale de la Recherche through the Santé Environnement – Santé Travail scheme (contract number 2006-SEST-22).Peer reviewe

Human transformations of the Wadden Sea ecosystem through time: a synthesis

Todayrsquos Wadden Sea is a heavily human-altered ecosystem. Shaped by natural forces since its origin 7,500 years ago, humans gradually gained dominance in influencing ecosystem structure and functioning. Here, we reconstruct the timeline of human impacts and the history of ecological changes in the Wadden Sea. We then discuss the ecosystem and societal consequences of observed changes, and conclude with management implications. Human influences have intensified and multiplied over time. Large-scale habitat transformation over the last 1,000 years has eliminated diverse terrestrial, freshwater, brackish and marine habitats. Intensive exploitation of everything from oysters to whales has depleted most large predators and habitat-building species since medieval times. In the twentieth century, pollution, eutrophication, species invasions and, presumably, climate change have had marked impacts on the Wadden Sea flora and fauna. Yet habitat loss and overexploitation were the two main causes for the extinction or severe depletion of 144 species (~20% of total macrobiota). The loss of biodiversity, large predators, special habitats, filter and storage capacity, and degradation in water quality have led to a simplification and homogenisation of the food web structure and ecosystem functioning that has affected the Wadden Sea ecosystem and coastal societies alike. Recent conservation efforts have reversed some negative trends by enabling some birds and mammals to recover and by creating new economic options for society. The Wadden Sea history provides a unique long-term perspective on ecological change, new objectives for conservation, restoration and management, and an ecological baseline that allows us to envision a rich, productive and diverse Wadden Sea ecosystem and coastal society

Contribution des données des images Landsat à l'étude structurale d'un secteur des Mauritanides, en Mauritanie du sud et au Sénégal oriental Contribution of Landsat Image Data to the Structural Surveying of a Sector of the Mauritanides Belt, in Southern Mauritania and Eastern Senegal

Effectuée grâce à l'obligeance de la Compagnie IBM-France, l'étude d'un tronçon des Mauritanides sur deux images du satellite Landsat-1, à l'aide du système interactif ERMAN II permet : 1) de caractériser sur les images les unités structurales classiquement reconnues dans cette région et de préciser leurs limites ; 2) d'envisager la définition d'une unité nouvelle située à la partie interne de la chaîne ; 3) de mettre en évidence et d'interpréter, notamment au Sénégal, un grand nombre de linéaments comme un ensemble de décrochements. Les interprétations proposées sont confrontées systémati-quement aux données de terrain. With the help of IBM-France, the online ERMAN II system was used to study part of the Mauritanides belt on two images taken by the Landsat 1 satellite. This survey was used: 1) To characterize the conventional structural units recognized in this region by means of the photos and to specify the exact boundaries of these units. 2) To consider defining a new unit inside the belt. 3) To reveal and interpret a great many lineaments as a group of transcurrent faults, especially in Senegal. The interpretations proposed are systematically compared with field data

Contribution des données des images Landsat à l'étude structurale d'un secteur des Mauritanides, en Mauritanie du sud et au Sénégal oriental

Effectuée grâce à l'obligeance de la Compagnie IBM-France, l'étude d'un tronçon des Mauritanides sur deux images du satellite Landsat-1, à l'aide du système interactif ERMAN II permet : 1) de caractériser sur les images les unités structurales classiquement reconnues dans cette région et de préciser leurs limites ; 2) d'envisager la définition d'une unité nouvelle située à la partie interne de la chaîne ; 3) de mettre en évidence et d'interpréter, notamment au Sénégal, un grand nombre de linéaments comme un ensemble de décrochements. Les interprétations proposées sont confrontées systémati-quement aux données de terrain

ESR studies on some spiropyrans, spironaphthopyrans, and spirooxazines

Biradicals were double-trapped by bubbling NO through benzene solutions of some photochromic spirocompounds; it would however appear that these species do not directly participate in the photochromic process. The ESR spectra of the radical anions of some nitrosubstituted spirocompounds indicated that there is no electronic interaction between the two moieties of the spiromolecules; reducing the substrates in the absence or in the presence of light leads to different ESR signals, but it cannot be excluded that the observed differences are only due to the different reaction media

Antioxidant activity of some simple phenols present in olive oil

The antioxidant activity of five phenols, i.e. catechol, homovanillyl alcohol, homovanillic acid, gallic acid and syringic acid, present in all olive oils has been investigated. For gallic acid and syringic acid the Bond Dissociation Enthalpy BDE(O-H) has been determined through the EPR (Electron Paramagnetic Resonance spectroscopy) based on radical equilibration technique as 81.0 and 82.1 kcal mol−1, respectively. For both homovanillyl alcohol and homovanillic acid the BDE(O-H) values were assumed to be identical to that of the similar 2-methoxy-4-methylphenol (82.8 kcal mol−1). The inhibition rate constants of the above compounds and of catechol in the autoxidation of cumene (or styrene) were also determined in acetonitrile/chlorobenzene solution and corrected for hydrogen bonding by acetonitrile. The results indicate that in organic solvents gallic acid and catechol are fairly good antioxidants, while homovanillyl alcohol, homovanillic acid and syringic acid, i.e. the three 2-methoxy substituted derivatives, are much less efficient antioxidants