Toute la réflexion contenue dans ces pages porte sur un seul postulat: peut-on prédire l'avenir? À partir de ce questionnement, se dessine la nécessité d'élaborer une ontologie du temps qui prend son assise non seulement dans la métaphysique, mais aussi dans la physique et la littérature. Cette dernière vient agir comme balise, puisque l'imaginaire se met au service d'une réflexion sur la structure même du temps à travers la représentation esthétique qu'une oeuvre d'anticipation en particulier traite comme objet du discours -soit Le Cycle de Dune de Frank Herbert. Puisque l'anticipation, en tant que sous-genre de la science-fiction, emprunte certaines de ces conceptions à la science exacte, cette balise esthétique particulière permet ainsi à cette ontologie du temps de référer directement à la science. L'oeuvre d'Herbert, parce qu'elle met en scène des protagonistes dotés de pouvoirs temporels, comme la prescience et la mémoire génétique, ouvre de facto la porte à une ontologie du temps qui s'articule selon quatre axes méthodologiques -chacun de ces chapitres renvoyant directement sa réflexion physique, métaphysique et littéraire à l'imaginaire dépeint dans la fiction du Cycle de Dune. Primo, une ontologie du futur, qui est rendue possible par une analyse de la prescience, cette capacité à voir le temps de manière omnisciente -laquelle omniscience permet d'élaborer un modèle physique du temps, ou plutôt de l'espace-temps, puisqu'il est démontré que temps et espace sont indissociables. Secundo, une ontologie de la mémoire et sa relation avec le passé et l'historicité, grâce à l'étude de la mémoire génétique qui révèle l'immortalité de cette mémoire, laquelle demeure néanmoins subjective et sujette, dans sa fonction de témoignage, au parjure. Tertio, une ontologie du présent, nuancée par une distinction entre le présent physique et le présent phénoménologique, ce dernier créant des conséquences particulièrement néfastes pour les protagonistes d'Herbert, soit une perte de repère temporel, un risque de possession et l'ennui causé par un futur décidé qui fixe le présent du prophète en un déterminisme figé. Quarto, un examen de la forme temporelle du Cycle de Dune, où les exergues adoptent une temporalité indépendante du reste de la narration qui rend cette dernière assimilable à un simulacre de récit, au point où, de façon surprenante, il devient possible d'affirmer que les exergues seraient le véritable présent diégétique, et la narration, une reconstruction du passé faussée par des preuves documentaires erronées et un éloignement temporel cinq fois millénariste. Finalement, il semble que l'avenir peut être prédit dans le modèle d'espace-temps ontologique proposé, mais qu'une telle prédiction est une arme à deux tranchants, une chose peu souhaitable parce que contraignant le prophète à déterminer, de façon figée, lequel des futurs possibles deviendra l'à venir du présent -comme les protagonistes d'Herbert le font dans le Cycle de Dune, afin d'assurer la survie de l'humanité par une corruption volontaire de la mémoire collective. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Ontologie de l'espace-temps, Le Cycle de Dune de Frank Herbert, Science-fiction, Science et littérature, Prédiction du futur, Histoire et mémoire collective, Phénoménologie du présent, Exergues et simulacre de récit.

Monospecific stands of Acacia karroo establish naturally on disturbed coastal dunes in KwaZulu-Natal, South Africa. While the A. karroo successional pathway is successful in rehabilitating mined dunes at the Richards Bay Minerals mining company (RBM), the same pathway has become arrested in the coastal dune forest at Cape Vidal in the Greater St. Lucia Wetland Park. This study examines the efficacy of the A. karroo successional pathway for restoring disturbed coastal dune forests. Dispersal of seeds and successful recruitment of seedlings are essential for habitat restoration. Seed and seedling banks were compared between previously disturbed A. karroo stands and adjacent forest at Cape Vidal. Different seed bank composition and higher seed bank richness in the forest suggest that seed dispersal into A. karroo stands is limited. Protected seed banks in A. karroo stands had increased seedling richness, indicating that dispersal limitation does not fully explain the lack of seedling establishment. At RBM, the seed bank richness of A. karroo stands increased with age since mining. While cumulative species richness of the seed bank of the oldest A. karroo stand at RBM was marginally lower than that at Cape Vidal, successful rehabilitation at RBM is associated with low seedling mortality. Consequently, forest tree species richness is high at RBM in the A. karroo stands and is converging on natural forest richness and composition. Although seed dispersal is reduced, it does not totally limit establishment of forest tree species in A. karroo stands at Cape Vidal, which implicates a post-establishment factor. Soil fertility potentially reduces seed germination and seedling growth. Soil nutrients in A. karroo stands at Cape Vidal were similar to those in the adjacent forest, and total nitrogen levels in A. karroo stands at Cape Vidal were higher than at RBM. Thus, soil conditions were unlikely to be limiting tree regeneration in A. karroo stands. Total nitrogen accumulated in the oldest stand at RBM at a rate of 10.0 g.m2.y(1 and a similarly rapid rate occurred at Cape Vidal. Therefore the A. karroo stands were not nitrogen limited. Nitrogen supplementation experiments at Cape Vidal demonstrated that a range of forest tree species establish in A. karroo stands regardless of nitrogen level, but there is low survival of seedlings. Thus, nitrogen availability is not arresting succession at Cape Vidal. Herbivory can also inhibit seedling recruitment. Selective feeding may enhance the persistence of species with defences against herbivory, such as A. karroo, ultimately altering the tree community composition. Browsing and trampling by large mammalian herbivores in A. karroo stands at Cape Vidal decreased survival and growth of forest tree seedlings. Large herbivores such as kudu, waterbuck, bushbuck and red duiker preferentially used the A. karroo stands as they offer abundant food and their topography allowed easy movement. This topdown pressure reduced recruitment, growth, and survival of seedlings of undefended species. Few wild herbivores occur at RBM, which allowed succession to proceed unhindered, ultimately restoring coastal dune forest at this site. Despite successful rehabilitation of coastal dune forest on mined dunes at RBM, limited seed dispersal and high levels of herb ivory have arrested succession at Cape Vidal. Thus, the A. karroo successional pathway must be implemented only after careful consideration of site-specific factors such as distance to a source of propagules and the intensity of herbivory in the system. In areas where herbivore densities are high, management interventions focusing on reducing herb ivory and encouraging visitation by seed dispersers are necessary for the successful use of this successional pathway. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2007.

Wave-dominated and mixed tidal and wave energy barrier islands are assumed to have characteristic dune topographies that link to their macroscale form. However, there has been no systematic attempt to describe the linkage between barrier island macroscale form and dune topography. The goal of this thesis was to investigate how dune topographies correspond to a number of barrier island morphologies found along the southeastern U.S. Atlantic coast. Macroscale process-form variables were used to classify 77 islands into seven morphologic clusters. Islands from each cluster were selected and sites characteristic of the range of dune topographies within islands were characterized using three methods: the frequency distribution of elevations, directional spatial autocorrelation of elevation at different distance classes, and FRAGSTATS indices summarizing the patch structure of elevations. Variables derived from each of these methods peaked in their ability to discriminate among barrier island morphologies when the islands were aggregated into three groups. An ordination of those variables revealed a two or three-fold grouping of barrier island dune types that approximated the traditional wave dominated and mixed energy barrier island morphologic classification. These findings suggest that dune topographies converge upon two to three configurations even within the heterogeneity in macroscale island morphology.

Cette thèse prend pour objet le concept et les modalités du destin tel qu'il est articulé dans le Cycle de Dune de Frank Herbert. Le destin est une des interrogations les plus anciennes de l'humanité. Initiatrice des grands questionnements de l'être sur sa liberté et sur lui-même, la pensée sur le destin est intimement liée au développement des civilisations. Marque des chan- gements majeurs au cœur de l'être, l'évolution du concept de destin se lie également avec les grandes découvertes scientifiques: les nouveaux savoirs sur la nature et le monde changent la manière qu'a l'humain de se considérer lui-même dans cet environnement; il se redéfinit avec chaque découverte, devient restrictif ou expansif, offre l'idée d'une liberté humaine inexistante ou ne souffrant d'aucune limite autre que la mort. Penser le destin, c'est penser l'humain dans sa plus intime conception. Sur cette toile de fond, la première partie de cette étude porte sur l'évolution du concept de destin dans la pensée occidentale, de la civilisation grecque à l'épo- que moderne, en passant par les réflexions métaphysiques sur le rôle de la transcendance dans la vie de l'humain. Au travers de cette étude diachronique, le destin est analysé afin de mettre en avant l'idée que l'individu cherche toujours plus de liberté dans son existence. La deuxième partie aborde l'évolution de la science et l'impact de cette évolution dans la pensée de l'humain sur le monde et lui-même. Dans le contexte de cette deuxième partie, la thèse explicite le rôle joué par la science, ainsi que par le discours de la science-fiction, dans les efforts humains de prendre en main son destin, de devenir de plus en plus libre. Enfin, dans la dernière partie, l'analyse du Cycle de Dune sous l'angle des trois personnages que sont Paul, Alia et Leto 2 met en avant une vision transhistorique du concept de destin, afin de pouvoir aborder son évolution prochaine, qui ne le limite plus à l'individu, mais qui place l'humain dans l'univers. / This thesis examines the concept and modalities of destiny as it is articulated in Frank Herbert's Dune series. Destiny constitutes one of humanity's most ancient themes. Instigator of the human being's wide-ranging questioning with regard to its freedom and selfhood, thought about destiny is intimately linked to the emergence of civilizations. As a sign of major changes in existence, the evolution of the concept of destiny is also linked with the important scientific discoveries: new knowledge about nature and the world change the way in which human be- ings consider themselves in their surrounding world; destiny is redefined at every discovery, becoming in turn limited or expansive, offering ideas of an inexistent human freedom or a freedom subjected to no limit other than death itself. Thinking about destiny means thinking about the human in what it holds most intimate. Against this backdrop, the first part of this study deals with the evolution of the con- cept of destiny in Western thought, from Greek civilization to the modern period, including metaphysical reflections on the role of transcendence in human life. Throughout this dia- chronic study, destiny is analyzed in emphasizing the notion of the individual’s attempt to in- crease human freedom. The second part takes on the evolution of science and the impact of its development on human thought about the world and humanity itself. In the context of this part, the thesis explicates the role played by science, as well as by the discourse of science fic- tion, in human efforts to take control of destiny and possess ever greater freedom. In the final part, by means of interpreting Dune’s three principal characters - Paul, Alia, and Leto 2 -, the analysis of the Dune series foregrounds a transhistorical perspective of the concept of destiny in order to trace out the imminent mutations of destiny that go beyond the individual, situating the human in the broader universe.

This thesis describes the geomorphology and morphodynamics of two embayed, sandy, macrotidal beach-dune systems in the Cape St. James region of Gwaii Haanas National Park Reserve and Haida Heritage Site. Gilbert Bay beach is a small embayment with a southwest aspect that exhibits prograding dune ridges. Woodruff Bay beach, a larger system with a SE aspect, is characterized by large erosional scarps on the established foredune. Aspect to erosive conditions and embayment size control the distinct morphologic responses of these beach-dune systems. The morphodynamic regime at Cape St. James consists of high onshore sediment transport potential combined with an increasingly erosive water level regime that is forced by PDO and ENSO climatic variability events. Conceptual models of potential future responses of these beaches to sea level rise show a possible landward migration of up to 3.5 m at Gilbert Bay beach and up to 4 m at Woodruff Bay beach.

Oceanic islands have been used as model systems for studies of evolution and speciation as the range of island sizes coupled with their known geological chronosequence make them ideal systems for the study of spatial and temporal variations in species diversity and distributions. These processes also occur on continental islands and mainland habitats but features of oceanic islands, notably their clearly delimited boundaries, natural isolation and simple geological composition make them more amenable to study. The perched dune lakes of Fraser Island, Australia share many of the properties of oceanic islands. The naturally isolated formation of the perched lakes, clearly delimited boundaries of the freshwater habitat and phase difference compared to the surrounding, terrestrial environment have significant implications for the biota these lakes support. Inhabitants of the perched dune lakes consist of the aquatic and semi-aquatic descendents of colonisers that were able to traverse a land barrier and survive in the oligotrophic, acidic waters over subsequent generations. Barriers to ongoing gene flow among lake populations, are however likely to be different for species with different life history characteristics. I therefore sought to assess the effects of three different life history characteristics on post-colonisation interpopulation gene flow. A representative species was selected to represent one of each of the following life history characteristics: * Aquatic species confined to lake for entire life cycle - freshwater shrimp Caridina indistincta. * Semi-aquatic species capable of terrestrial dispersal - freshwater turtle Emydura krefftii. * Semi-aquatic species capable of aerial dispersal - odonate Orthetrum Boumiera. 137-250 individuals were sampled per species across six lakes separated by 1-6km. Regions of the mitochondrial genome were targeted and molecular screening methods developed and employed to assess the relative levels of post-colonisation gene flow among lake populations. Parsimony analysis of the 25 unique haplotypes identified in the species with no apparent inter-lake dispersal mechanism, the freshwater shrimp Caridina indistincta, demonstrated that there was no sharing of derived haplotypes among lake populations. Star shaped genealogies were identified in four lake populations indicative of a population expansion and mismatch distribution analysis confirmed a recent population expansion estimated to have occurred no more than 200,000 years ago. This demonstrates that each of the perched dune lakes was colonised by C.indistincta soon after their inception but that no ongoing gene flow among lake populations has occurred. The population genetic structure of the species assessed which is capable of terrestrial dispersal suggests that although this species of freshwater turtle, Emydura krefftii, is capable of overland dispersal, gene flow among lake populations is limited. Even at the small spatial scale examined in this study, E.krefftii populations displayed a pattern of isolation by distance (r=0.854, p&lt0.03). Nested clade analysis also suggested a pattern of restricted gene flow with some long distance dispersal in recent times with long distance dispersal and a possible range expansion occurring historically. The species examined in this study that displayed the most extensive gene flow among lake populations was the dragonfly Orthetrum boumiera. No relationship was found between genetic and geographic distance (r= -0.0852, p&gt0.05) and nested clade analysis could not identify a geographical association among haplotypes, indicative of panmixia. While larval life stages of this species are fully aquatic, the winged adult stages of this species appear to be connecting seemingly isolated lake populations, at least at the spatial scale examined here. The results of this study have demonstrated that these perched dune lakes provide 'island like' models for recent biogeographic processes. The pattern of colonisation and subsequent diversification identified in these populations takes the form of insitu 'genetic radiations' with those populations that are isolated forming monophyletic clades endemic to a single lake. The genetic diversity and endemism identified in this study has occurred over much smaller temporal (&lt500,000 years) and spatial (&lt6.5km) scales than in studies of oceanic island fauna. However, the mode of formation of the perched dune lakes and the implications that their natural isolation and abiotic genesis have for the evolution of colonisers of these unique habitats has resulted in them being analogous to true oceanic islands.

This thesis describes the geomorphology and morphodynamics of two embayed, sandy, macrotidal beach-dune systems in the Cape St. James region of Gwaii Haanas National Park Reserve and Haida Heritage Site. Gilbert Bay beach is a small embayment with a southwest aspect that exhibits prograding dune ridges. Woodruff Bay beach, a larger system with a SE aspect, is characterized by large erosional scarps on the established foredune. Aspect to erosive conditions and embayment size control the distinct morphologic responses of these beach-dune systems. The morphodynamic regime at Cape St. James consists of high onshore sediment transport potential combined with an increasingly erosive water level regime that is forced by PDO and ENSO climatic variability events. Conceptual models of potential future responses of these beaches to sea level rise show a possible landward migration of up to 3.5 m at Gilbert Bay beach and up to 4 m at Woodruff Bay beach.

Esta tese é uma compilação de diversos estudos que relatam as características e as mudanças encontradas nas praias do Rio Grande do Sul (RS). Destaca os princípios da gestão integrada dos ambientes costeiros e as práticas utilizadas em praias e dunas, auxiliando neste tema interdisciplinar, e colaborando desta forma com um caminho que conduza esta região a um desenvolvimento econômico e social com a manutenção das características naturais. As praias do RS têm atraído as pessoas para a costa há mais de um século, assim como um grande número de visitantes aos balneários e áreas turísticas, durante períodos de férias e lazer. A utilização deste ambiente tem sido de importância crescente para a economia dos municípios litorâneos, sendo que a gestão destas áreas tornou-se necessária para lidar com uma variedade de problemas. Exemplos destes problemas e da preocupação das pessoas que buscam a costa estão relacionados aos processos de erosão, que diminuem a beleza do ambiente, o espaço disponível para o lazer, e expõe a população a riscos de inundação; além disso, a presença de resíduos sólidos (lixo) e de efluentes domésticos a céu aberto traz preocupação com a saúde dos frequentadores. Esta tese inclui uma análise das causas da degradação da praia de Xangrilá, e oferece técnicas e respostas sobre como lidar com a reconstrução do ambiente erodido, principalmente o sistema de dunas, assim como os problemas enfrentados durante este processo, como resultado de efeitos adversos. Nos últimos anos estas práticas tornaram-se amplamente utilizadas no mundo, como um meio de manter ou melhorar as funções naturais de proteção das infra-instrutoras posicionadas próximas deste ambiente. Considerando que a gestão de praias e dunas será mais eficaz se os interessados (gestores, moradores e frequentadores) entenderem a sua funcionalidade ambiental, a importância na proteção da costa, e as alterações que estão ocorrendo, são relatados nos diversos artigos desta tese questões referentes às problemáticas da presença de resíduos sólidos, a dispersão de espécies exóticas, assim como as ferramentas disponíveis aos gestores costeiros para desenvolver suas políticas, voltadas especificamente para esta região, e sugestões de dinâmicas para estimular a percepção e o entendimento do ambiente. / This thesis is a compilation of several papers that include the features and changes found on the beaches of Rio Grande do Sul (RS). It focuses on the principles of integrated management of coastal environments and practices on beaches and dunes, collaborating in this way on a path leading to an economic and social development keeping the natural features. The beaches of RS have attracted people to the coast for more than two centuries, and a large number of people visit the beaches along the seaside each year for holidays and leisure. Beach utilization has been of increasing importance to the economies of these towns, and the beach management has become necessary to deal with a variety of problems that have appeared. Examples of these problems and concerns are related to beach erosion, which reduces the beauty of the environment, the space available for beach recreation as well as the exposure of people to risks of flooding; and the presence of solid waste (garbage) and open sewers, which brings concerns about the health of the regulars. The thesis includes an analysis of the causes of beach erosion in the city of Xangri-lá, and offers techniques and answers about how to deal with the reconstruction of the environment eroded, especially the dune system, as well as the problems faced during this process as a result of adverse effects. In recent years, these practices have become widely used worldwide as a means of keeping or improving the natural functions of protecting infrastructure placed near this environment. Whereas the management of beaches and dunes will be more effective if the stakeholders (managers, residents and regulars) understand its functionality, importance, and the changes that are occurring, in various articles of this thesis problematic issues concerning the presence of solid waste are reported, the spread of exotic species, as well as the tools available to coastal managers to develop their policies, fitted specifically to this region, as well as suggestions to stimulate dynamic awareness and understanding of the environment.

No Litoral Norte do Rio Grande do Sul, ao norte do balneário Xangri-lá, a barreira holocênica encontra-se parcialmente coberta pela fase moderna e relativamente ativa de um campo de dunas transgressivo, enquanto que, ao sul deste balneário, o campo de dunas cobre completamente a barreira. Este trabalho contribuiu para o conhecimento acerca desse comportamento diferenciado de desenvolvimento da fase moderna do campo de dunas transgressivo sobre a barreira holocênica. Foram utilizadas séries temporais de vento (direção e velocidade) e precipitação de estações meteorológicas localizadas ao sul e ao norte de Xangri-lá, bem como foram realizadas medições simultâneas de vento, por meio de anemômetros portáteis, imediatamente ao norte e ao sul desse balneário. Potenciais de transporte de areia foram calculados para ambas as estações meteorológicas. Os registros históricos da estação de Tramandaí (mais ao sul) indicaram maiores velocidades de vento e menores de precipitação em relação à estação de Torres (mais ao norte). Devido a maior velocidade dos ventos em Tramandaí, o potencial de transporte de areia nessa localidade foi superior a Torres, indicando o favorecimento da migração das dunas em suas proximidades. O comportamento desigual de desenvolvimento da fase moderna do campo de dunas transgressivo pode então estar relacionado a maior velocidade e frequência dos ventos NNE, NE, ENE e E em Tramandaí (ou seja, ao sul de Xangri-lá), além da menor precipitação que também favorece um transporte de areia mais eficiente ao sul de Xangri-lá. / In the north coast of Rio Grande do Sul, to the north of Xangri-lá beach, the Holocene barrier is partially covered by the modern and relatively active phase of a transgressive dune field, while to the south of this balneario the dune field completely covers the barrier. This work contributed to the knowledge about this differentiated development behavior of the modern phase of the transgressive dune field on the holocene barrier. Time series of wind (direction and speed) and precipitation of meteorological stations located to the south and north of Xangri-lá were used, as well as simultaneous wind measurements using portable anemometers, immediately to the north and south of this balneario. Sand transport potentials were calculated for both meteorological stations. Historical records of the Tramandaí station (further south) indicated higher wind speeds and lower precipitation relative to the Torres station (further north). Due to the greater speed of the winds in Tramandaí, the potential of sand transport in this locality was higher than Torres, indicating the favor of the migration of the dunes in its proximities. The uneven developmental behavior of the modern phase of the transgressive dune field can then be related to the higher speed and frequency of the NNE, NE, ENE and E winds in Tramandaí (ie, south of Xangri-lá), as well as the lower precipitation also favors more efficient sand transportation south of Xangri-lá.

No Litoral Norte do Rio Grande do Sul, ao norte do balneário Xangri-lá, a barreira holocênica encontra-se parcialmente coberta pela fase moderna e relativamente ativa de um campo de dunas transgressivo, enquanto que, ao sul deste balneário, o campo de dunas cobre completamente a barreira. Este trabalho contribuiu para o conhecimento acerca desse comportamento diferenciado de desenvolvimento da fase moderna do campo de dunas transgressivo sobre a barreira holocênica. Foram utilizadas séries temporais de vento (direção e velocidade) e precipitação de estações meteorológicas localizadas ao sul e ao norte de Xangri-lá, bem como foram realizadas medições simultâneas de vento, por meio de anemômetros portáteis, imediatamente ao norte e ao sul desse balneário. Potenciais de transporte de areia foram calculados para ambas as estações meteorológicas. Os registros históricos da estação de Tramandaí (mais ao sul) indicaram maiores velocidades de vento e menores de precipitação em relação à estação de Torres (mais ao norte). Devido a maior velocidade dos ventos em Tramandaí, o potencial de transporte de areia nessa localidade foi superior a Torres, indicando o favorecimento da migração das dunas em suas proximidades. O comportamento desigual de desenvolvimento da fase moderna do campo de dunas transgressivo pode então estar relacionado a maior velocidade e frequência dos ventos NNE, NE, ENE e E em Tramandaí (ou seja, ao sul de Xangri-lá), além da menor precipitação que também favorece um transporte de areia mais eficiente ao sul de Xangri-lá. / In the north coast of Rio Grande do Sul, to the north of Xangri-lá beach, the Holocene barrier is partially covered by the modern and relatively active phase of a transgressive dune field, while to the south of this balneario the dune field completely covers the barrier. This work contributed to the knowledge about this differentiated development behavior of the modern phase of the transgressive dune field on the holocene barrier. Time series of wind (direction and speed) and precipitation of meteorological stations located to the south and north of Xangri-lá were used, as well as simultaneous wind measurements using portable anemometers, immediately to the north and south of this balneario. Sand transport potentials were calculated for both meteorological stations. Historical records of the Tramandaí station (further south) indicated higher wind speeds and lower precipitation relative to the Torres station (further north). Due to the greater speed of the winds in Tramandaí, the potential of sand transport in this locality was higher than Torres, indicating the favor of the migration of the dunes in its proximities. The uneven developmental behavior of the modern phase of the transgressive dune field can then be related to the higher speed and frequency of the NNE, NE, ENE and E winds in Tramandaí (ie, south of Xangri-lá), as well as the lower precipitation also favors more efficient sand transportation south of Xangri-lá.