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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Mass Ethics : En undersökning om att använda spelserien Mass Effect inom etikundervisningen i religionskunskapen på gymnasieskolan / Mass Ethics : A study on using the Mass Effect games when teaching normative ethics in the religious education of upper-secondary school

Moberg, Daniel January 2015 (has links)
Skolverket menar att populärkultur, däribland dataspel, är användbara verktyg för att nå elevernas livsvärldar i religionskunskapsundervisningen. Den här uppsatsen undersöker den religionsdidaktiska potentialen hos Mass Effect-spelen i gymnasieskolan utifrån följande frågeställningar: Får rätt och fel handling något utrymme i Mass Effect? På vilket sätt? Vad är rätt och fel i spelkontexten? Kan Mass Effect fungera som stödstruktur för att arbeta med stoff och förmågor som är en del av religionskunskapens etikundervisning och i sådana fall på vilket sätt? Spelkontexten utforskas genom en analys av hur spelens Paragon/Renegade-system bedömer olika handlingar. Systemet jämförs med plikt-, konsekvens- och dygdetiska förhållningssätt; dessa är etiska modeller som tas upp av styrdokumenten. En av spelens beslutssituationer granskas också utifrån en beslutsmodell och styrdokumentens etiska modeller bidrar här med teoretisk och kursplanemässig förankring. Undersökningen visar att flera av de områden som ska ingå i gymnasieskolans etikundervisning kan beröras genom att låta olika element i Mass Effect-spelen möta ämnets stoff. Processen verkar ur ett didaktiskt perspektiv både berikande för spelkontexten och illustrerar komplexiteten hos etiska modeller och fattandet av etiska beslut. Resultatet är i linje med varför styrdokumenten rekommenderar användandet av populärkultur och arbetssättet förespråkas även utifrån tidigare forskning. / According to the Swedish National Agency for Education, popular culture, in which computer games are included, is a useful tool for connecting with the students and their worlds when teaching the subject of religion. This essay explores the potential of the Mass Effect-games to serve as an instrument when teaching the subject of religion, aiming to answer the following questions: Does right and wrong play a part in Mass Effect? How? What is right and wrong in the context of the game? Can Mass Effect be used as a framework when teaching the ethical content of the religious subject and if so, how? The context of the games is explored through an analysis of how their reputation system, here called the Paragon/Renegade-system, judges different actions, and through a breakdown of one of the decisions in the games, using a model designed for analyzing ethical issues. This context is then compared with ethical models appearing in the syllabus for the subject of religion and the knowledge and abilities that the subject should offer the students opportunities to develop. The research shows that much of the core content of ethical studies can be addressed using the various elements of the Mass Effect-games. On the basis of other studies, this kind of work is also encouraged.
12

Vývoj reprezentace LGBT menšiny v počítačových příběhových RPG hrách a přijímání homosexuální tématiky hráči a herními vývojáři / Progress in the representation of the LGBT minority in RPG videogames and accepting of queer topics by gamers and game-developers

Moravec, Ondřej January 2014 (has links)
Diploma thesis "Progress of representation of the LGBT minority in RPG-story-based PC games and accepting the homosexual themes by gamers and game developers" deals with new way of representation of LGBT minority via videogames. While traditional media as film or literature are able to narrate only by the linear way, with the development of RPG genre the new ergodic literature appeals. This style of narration has many ways which you can follow - and one of them is also the way of playing with LGBT character - the way which can be close for some other players. Work combines a few views on this problem - how does the language of videogames support such ideas? How game developers are interested in this matter? And what about the homosexual gamers - what do they want? This works also include the analysis of the video games, which changed the view on the representation of LGBT minority in videogames (Mass Effect I-III, Dragon Age I-II). The goal of this work is to offer the first compact text on this topic in Czech but even also in world context. Powered by TCPDF (www.tcpdf.org)
13

Importance des processus de dispersion dans la structuration spatiale des communautés de diatomées benthiques des cours d’eau, à l’échelle intercontinentale : implications en termes de biodiversité et de tolérance / The importance of dispersion processes in the spatial structure of benthic diatom communities in rivers, at an intercontinental scale : implications for biodiversity and vulnerability

Leboucher, Thibault 14 December 2018 (has links)
La structuration des communautés biotiques apparaît aujourd’hui comme étant le résultat d’une interaction entre processus déterministes et stochastiques. Le species sorting, c’est-à-dire le couplage de l’influence des filtres environnementaux et des interactions biotiques, ainsi que les processus de dispersion apparaissent comme des facteurs déterminants pour la structuration des communautés, mais leur importance relative est encore mal comprise car conditionnée par les échelles spatiales, et les niveaux d’anthropisation considérés. Si des approches quantitatives multi-échelles sont donc vivement recommandées pour mieux comprendre comment les processus locaux et régionaux affectent les communautés, celles-ci sont encore trop rares dans la littérature. Nous avons ainsi tenté de mettre en place ce type d’étude, en prenant comme organisme modèle les diatomées, producteurs primaires jouant un rôle clef au sein des écosystèmes aquatiques. L’objectif était d’appréhender le rôle des processus déterministes et stochastiques dans la structuration des méta-communautés de diatomées benthiques en cours d’eau soumises à différents niveaux d’eutrophisation, de l’échelle locale à l’échelle intercontinentale. A l’aide de bases de données françaises et américaines comprenant plus de 4 000 stations d’échantillonnage, ce travail a permis de mettre en évidence une forte influence de l’eutrophisation tout au long du gradient spatial d’observation, induisant une baisse de la diversité beta. La structuration des communautés diatomiques est de plus apparue fortement influencée par les processus déterministes locaux (species sorting) aux faibles niveaux d’anthropisation, puis par les processus de dispersion lorsque le niveau trophique augmentait. La dispersion limitée et l’effet de masse sont les deux processus évoqués pour expliquer cette forte influence de la dispersion sur la structuration des communautés. L’effet de masse permet à une espèce de subsister en dehors de son optimum environnemental grâce à l’arrivée constante d’individus via un processus d’immigration, induisant de fait une forte homogénéisation des communautés. Si la dispersion limitée est plutôt bien appréhendée aujourd’hui dans la littérature, l’effet de masse restait jusqu’ici difficile à mettre en évidence, constituant un verrou scientifique important à lever. Nos travaux ont permis de développer une méthode innovante capable de mesurer l’influence de ce processus sur les communautés de disperseurs passifs que sont les diatomées. Une meilleure compréhension de ce mécanisme représente une avancée conséquente, notamment dans le cadre du déclin mondial de la biodiversité. Ce phénomène impacte également significativement les méthodes de bio-indication de la qualité des milieux puisque la présence d’espèces dans des habitats qui leur sont a priori peu favorables peut potentiellement masquer l’effet des conditions locales du milieu sur les communautés, et ainsi induire un biais dans l’évaluation de l’état écologique des cours d’eau. Nos résultats vont dans ce sens, en révélant que la prise en compte de ce processus dans le calcul de l’Indice Biologique Diatomées permet une réponse plus fine de l’indice à l’environnement local, mettant ainsi en évidence l’importance de prendre en compte les processus de dispersion lors de l’élaboration de nouvelles méthodes de bio-indication. / The structuration of biotic communities is generally caused by an interplay between stochastic and deterministic processes. Species sorting, i.e. environmental filtering coupled with biological interactions, and dispersal processes are particularly important divers of communities, however, their relative influence are constrained by the effects of spatial scale and therefore poorly understood. Quantitative multi-scales approaches are thus recommended to better understand how local and regional processes affect communities. However, few studies have actually implemented quantitative scale-explicit frameworks to explore such relationships. This is one of our aims here, to quantify the relative contributions of local community assembly processes vs. stochastic processes in driving benthic diatom communities, and to assess how spatial scale and anthropogenic disturbance interact to dictate which driver dominates. Using French and US databases encompassing more than 4 000 spatially distinct localities, this work provides strong evidences stating that nutrient supply mediated community structuring whatever the scale considered. Nutrient enrichment was associated with an overall decline in diatom beta-diversity and a shift in assembly processes from species sorting to dispersal. Dispersal limitation and mass effect are the two major dispersal processes acting on diatom communities. While dispersal limitation can be detected by experimental or modeling techniques, mass effect is more challenging to detect as it can allow species to persist in unfavorable habitats, i.e. far away from their environmental optimum. Here, we developed an innovative and robust method for the detection of this process for passive dispersers, such as diatoms. Beyond its importance in the taxonomic homogenization, causing extensive impairment of freshwater ecosystems, mass effect is also evoked for its potential impact on bio-assessment methods. Our results largely supported the idea that mass effect may induce a biased evaluation of water quality, since taking into account this process for the calculation of the Biological Diatom Index leads to a more acute assessment of river ecological status. We then advocate for a better integration of spatial mechanisms in any diatom-based indices, and by extension in any biotic index based on passive dispersers.
14

An Investigation On Dynamic Contact Parameters In Machining Center Spindle

Ozsahin, Orkun 01 November 2008 (has links) (PDF)
In machining centers, with the increasing trends in high precision machining, chatter has become an important problem which results in poor surface finish and low material removal rate. Chatter can be avoided with stability diagrams which provide the stable regions in the machining process for the depth of cut and spindle speed combinations. In order to obtain stability diagrams, tool point frequency response function (FRF) of the system should be obtained. Throughout this study, contact parameters which are the most critical part of the analytical modeling of spindle-holder-tool assembly in order to obtain tool point FRF, are examined. For the accurate identification of the contact parameters, a recently suggested closed form approach based on measured FRFs is improved and applied to real structures by solving several application problems. In addition to the identification of contact parameters from experimental results, in order to eliminate the dependency on experiments, artificial neural networks are used to predict contact parameters for cases for which no experiments were carried out. By using trained neural network, contact parameters are predicted for the first seen combination of tool gauge length and diameter with a high accuracy. Such an application will have an important contribution to the machining stability studies since elimination of dependency on experiments will make it possible to predict stability diagrams for different combinations of spindle, holder and tool without performing any experiments. Additionally, since accurate identification of contact parameters, thus tool point FRFs and stability diagrams are highly dependent on accuracy of the performed experiments, possible errors due the mass of the accelerometers are also investigated. In order to compensate the mass effect of the accelerometers, a structural modification with matrix inversion method is applied to the accelerometer based results.
15

Influência das condições oceanográficas sobre a estrutura da comunidade fitoplanctônica no Atol das Rocas, Atlântico Sul Equatorial, Brasil

JALES, Marina Cavalcanti 24 August 2015 (has links)
Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-04-13T13:00:14Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Influência das condições oceanográficas sobre a estrutura da comunidade fitoplanctônica no Atol das Rocas, Atlântico Sul ~1.pdf: 2936800 bytes, checksum: 5a792d6404a0184ffa0f103bd5901478 (MD5) / Made available in DSpace on 2016-04-13T13:00:14Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Influência das condições oceanográficas sobre a estrutura da comunidade fitoplanctônica no Atol das Rocas, Atlântico Sul ~1.pdf: 2936800 bytes, checksum: 5a792d6404a0184ffa0f103bd5901478 (MD5) Previous issue date: 2015-08-24 / O conhecimento da composição e distribuição dos produtores primários é fundamental para uma melhor compreensão da dinâmica trófica de regiões oceânicas. A composição do fitoplâncton no Oceano Atlântico Sul ainda está sendo explorada e em algumas regiões esta diversidade nunca foi descrita, como é o caso da Reserva Biológica do Atol das Rocas. O atol situa-se ao sul do equador (3°51’S e 33°49’W), distante 143 milhas náuticas da Cidade de Natal, Estado do Rio Grande do Norte (Brasil). Este estudo teve como principal objetivo caracterizar a estrutura da comunidade fitoplanctônica do entorno e nas piscinas naturais do Atol das Rocas correlacionando com as variáveis ambientais. As amostras foram coletadas no entorno do atol em julho de 2010, utilizando o navio Oceanográfico da Marinha do Brasil, Cruzeiro do Sul. Dois transectos foram estabelecidos de acordo com a corrente superficial, um transecto em direção sudeste (SE) e o outro, em direção noroeste (NO) do atol. Nestes transectos foram determinados três pontos de coleta para cada um. As amostras foram coletadas em diferentes profundidades (superfície e PMC – Profundidade Máxima de Clorofila) e diferentes períodos do dia (dia e noite). Nas piscinas naturais analisadas (Barretinha, Cemitério, Tartarugas, Rocas e Barretão), as coletas ocorreram em períodos climáticos distintos nos anos de 2012 e 2013. Os parâmetros oceanográficos os quais foram empregados para analisar a influência sobre a estrutura do fitoplâncton foram salinidade, temperatura da água, oxigênio dissolvido, teores de nutrientes inorgânicos dissolvidos e clorofila a. Foram realizadas coletas para a análise do microfitoplâncton utilizando rede com malha de 20 μm e densidade fitoplanctônica utilizando garrafa de Niskin. No entorno do atol, a maioria das variáveis ambientais apresentou aumento significativo em função da turbulência no transecto NO. Pode-se observar que houve aumento dos teores de clorofila a e nutrientes, e redução da temperatura e oxigênio na camada de mistura em função da influência da ACAS (Água Central do Atlântico Sul). No transecto NO a comunidade fitoplanctônica correlacionou-se fortemente com os parâmetros salinidade e temperatura, devido a uma instabilidade termohalina decorrente da interação das massas d’água Água Tropical e a Água Central do Atlântico Sul. As amostras apresentaram variação espacial horizontal, com maior participação do filo Ochrophyta próximo ao atol e Dinophyta nos pontos mais distantes, enquanto que na distribuição vertical não houve diferença. Espécies mais abundantes foram Prorocentrum balticum (Lohmann) Loeblich 1970, P. compressum (Bailey) Abéex Dodge 1975 e P. gracile Böhm 1933 e Coccolithus sp.. Já nas piscias naturais, apesar do filo Ochrophyta ter sido o mais evidenciado, as espécies mais representativas encontradas de acordo com a densidade foram Prorocentrum balticum (Lohmann) Loeblich 1970, P. lima (Ehrenberg) F. Stein 1878, Pyrophacus sp. e Ostreopsis ovata Fukuyo 1981. De um modo geral, quatro diferentes filos foram identificados com um total de 195 taxa. No entorno do Atol das Rocas, o aumento de biomassa fitoplanctônica no transecto NO, foi provocado pelo “efeito ilha” e não pela ressurgência. Além disso, as condições oceanográficas influenciaram na distribuição da comunidade fitoplanctônica. Nas piscinas naturais, apesar da composição apresentar diferença espacial, nenhum parâmetro hidrológico foi determinante. No entanto, pode-se observar um padrão sazonal, havendo um aumento quali-quantitativo do fitoplâncton no período chuvoso, no qual, o hidrodinamismo local, proporcionou condições mais favoráveis para o enriquecimento da diversidade, com ênfase nas espécies que compõem a microflora bentônica. / Knowledge of the composition and distribution of primary producers is essential to understand the trophic dynamics of ocean food webs. The composition of phytoplankton in the South Atlantic Ocean is still being explored, and in some regions this diversity has never been described, as in the case of Biological Reserve of Atol das Rocas. The atoll is located in south of the equator (3°51’S and 33°49’W), some 143 nautical miles from the city of Natal, in the state of Rio Grande do Norte (Brazil). The aim of this paper is to characterize the phytoplankton community structure in the natural pools of Atol das Rocas and its surrounding area by correlating environmental variables. The samples were collected around the atoll in July 2010 on board the Brazil Navy Oceanographic ship, the Cruzeiro do Sul. Two transects were established according to the surface current; a transect oriented southeast (SE) and a transect oriented northwest (NW) of atoll. Three collection points were established for each of the transects. The samples were collected at different depths (surface and DCM - Deep Chlorophyll Maximum) and during different periods of the day (daytime and nighttime). Sampling occurred at the pools Barretinha, Cemitério, Tartarugas, Rocas and Barretão in different climate periods of 2012 and 2013. Oceanographic parameters which were used to analyze the influence on phytoplankton structure were salinity, water temperature, dissolved oxygen, dissolved inorganic nutrients content and chlorophyll a. Samples were collected to analyse microphytoplankton using mesh net of 20μm and phytoplankton density using bottle Niskin. Around the atoll, most of the environmental variables increased significantly due to turbulence in NW transect. Increased contents of chlorophyll a and nutrients and a reduction of temperature and oxygen in the mixing layer were also detected due to the influence of the SACW (South Atlantic Central Water). In the NW transect, the phytoplankton community corresponded strongly with the salinity and temperature parameters due to thermohaline instability resulting from the interaction of Tropical Water masses and Central Water masses of the South Atlantic. The samples presented a horizontal spatial variation, with highest participation of the phylo Ochrophyta closer to the atoll and Dinophyta further from the atoll, while vertical distribution patterns were not observed. The most representative species were Prorocentrum balticum (Lohmann) Loeblich 1970, P. compressum (Bailey) Abéex Dodge 1975 and P. gracile Böhm 1933, and Coccolithus sp.. The predominant group in the natural pools was Ochrophyta. In spite of the predominance of this group, the most representative species found in the pools in terms of density were Prorocentrum balticum (Lohmann) Loeblich 1970, P. lima (Ehrenberg) F.Stein 1878, Pyrophacus sp. and Ostreopsis ovata Fukuyo 1981. In general, four different phyla were identified with a total of 195 taxa. In the area surrounding Atol das Rocas, an increase in phytoplankton biomass in transect NW was caused by the "island effect" and not by the upwelling. Furthermore, the oceanographic conditions influenced the distribution of the phytoplankton community. Despite the spatial difference of the composition found in the natural pools, there was no determinant hydrological parameter. However, a seasonal pattern was observed, with a qualitative and quantitative increase of phytoplankton during the rainy season when the local hydrodynamics provides more favourable conditions for the enrichment of diversity, especially among species that compose the benthic microflora.
16

The Mechanics of War: Procedural Rhetoric and the Masculine Subject in the Gears of War and Mass Effect Series

Snyder, Shane Michael 14 October 2015 (has links)
No description available.
17

Développement d'un modèle numérique de couplage fluide-structure appliqué au cas d'une pompe à membrane ondulante / Development of a numerical model using fluid-structure interaction method apply to an undulating membrane pump

Song, Mengdi 20 June 2013 (has links)
Dans cette thèse, nous avons étudié la simulation numérique des phénomènes d’interaction fluide-structure (IFS) par la méthode des éléments finis pour un fluide incompressible et non visqueux en interaction avec une structure flexible. Les modèles numériques développés sont basé sur une approche d’IFS partitionnée. Une amélioration basée sur une compensation des effets de massé ajoutée est proposée au cours de la thèse afin d’assurer la convergence et la stabilité du schéma de couplage partitionné indépendamment de la densité du fluide impliqué. L’approche corrective nécessite une estimation de la matrice de masse ajoutée et demande une légère modification de l’algorithme itératif. Les méthodes proposées ont été validées sur les cas académiques en comparaison avec les solutions analytiques et sont appliqués au cas d’une nouvelle conception de pompe pour tout type de fluides (gaz, liquides, fluide chargé…), en vue d’affiner la compréhension de son fonctionnement et ainsi mieux la caractériser. Les méthodes ainsi que les validations sont publiées sur un article qui a été accepté par le revue scientifique « Computers & Fluids ». Une présentation orale a effectuée pendant la conférence internationale ACE-X2012 à Istanbul et une autre a été accepté par la conférence nationale CSMA-2013 à Giens. / The numerical simulation of fluid-structure interaction (FSI) by the finite element method has been studied in the context of an incompressible and inviscid flow interacting with a very flexible structure.The numerical models developed in this work are based on a partitioned FSI approach. An improvement based on a compensation of the added-mass effect is proposed during the PhD research in order to ensure the convergence and the stability of the partitioned coupling scheme for all fluids regardless of its density. This simple correction requires to estimate the added-mass matrix and to modify slightly the iterative algorithm.The proposed methods were validated by comparing with analytical solutions for several academic cases and are applied to a novel pumping technology, which is applicable to all kinds of fluid (gas, liquid, slurry...). The main objective is to provide a better understanding about its operations and to improve the designing of pump. The methods and the validation cases are published in an article which has been accepted by the scientific review Computers & Fluids. They were also presented during the international conference ACE-X2012 in Istanbul and have been accepted and scheduled for oral presentation during the national conference CSMA-2013 in Giens.
18

The Expanding Storyworld : An Intermedial Study of the Mass Effect novels

Sundin, Jessika January 2018 (has links)
This study investigates the previously neglected literary phenomenon of game novels, a genre that is part of the increasing significance that games are having in culture. Intermedial studies is one of the principal fields that examines these types of phenomena, which provides perspectives for understanding the interactions between media. Furthermore, it forms the foundation for this study that analyses the relation between the four novels by Drew Karpyshyn (Mass Effect: Revelation, 2007; Mass Effect: Ascension, 2008; Mass Effect: Retribution, 2010) and William C. Dietz (Mass Effect: Deception, 2012), and the Mass Effect Trilogy. Differences and similarities between the media are delineated using semiotic theories, primarily the concepts of modalities of media and transfers of media characteristics. The thesis further investigates the narrative discourse, and narrative perspectives in the novels and how these instances relate to the transferred characteristics of Mass Effect. Ultimately, the commonly transferred characteristic in the novels is the storyworld, which reveals both differences and similarities between the media. Regardless of any differences, the similarities demonstrate a relationship where the novels expand the storyworld.
19

Influência de variáveis de paisagem sobre a riqueza e composição de assembleias de peixes em lagoas costeiras no sul do Brasil

Guimarães, Taís de Fátima Ramos January 2013 (has links)
Lagoas costeiras são ecossistemas dinâmicos caracterizados por uma alta biodiversidade, e podem ser vistos como manchas de hábitats na paisagem. Potencialmente, as características das comunidades em lagoas podem ser explicadas por teorias ecológicas (Biogeografia de Ilhas e Ecologia de Metacomunidades), onde o grau de isolamento e a heterogeneidade do hábitat em escala da paisagem são fatores importantes na determinação da comunidade. O objetivo deste trabalho foi verificar a influência destes fatores sobre diferentes descritores da comunidade (abundância, diversidade alfa e beta) de peixes em lagoas costeiras, utilizando métricas de paisagem. A área de estudo localiza-se no sistema do rio Tramandaí, RS (50,14°O; 29,98°S), possui 41 lagoas com diferentes graus de conexão e comunica-se com o mar através do estuário de Tramandaí. As variáveis de paisagem foram obtidas através de sistemas de informação geográfica (imagens Spot e Landsat-TM5) e foram divididas entre variáveis estruturais (área, forma, distância do mar, coeficiente de variação da área, conectividade primária e conectividade estuarina) e variáveis de uso e cobertura da terra (buffer de 50, 100, 250 e 500 m). Dados de ictiofauna foram obtidos através de amostragem padronizada com rede de espera e de arrasto em 38 lagoas. Nossos resultados mostram que diferentes descritores da comunidade respondem a diferentes variáveis de paisagem. Quando considerada a composição de assembleias que habitam diferentes porções do corpo d’água observamos que 18% da variação nas assembleias de margens rasas são explicadas pelas variáveis estruturais e de uso e cobertura; já assembleias que habitam margens mais profundas respondem apenas as variáveis estruturais, as quais explicam 7% da variação nessa assembleia. Ambas as assembleias possuem partição de variância equilibrada entre variáveis que representam o isolamento e a heterogeneidade da paisagem. No entanto, quando consideramos outros descritores da comunidade como diversidade alfa e beta, observamos que as variáveis estruturais e de uso e cobertura da terra são mais importantes para explicar a diversidade dentro do corpo d’água (alfa), não sendo significantes para predizer a diversidade entre corpos d’água (beta). Esses resultados nos sugerem que as assembleias de peixes de lagoas costeiras podem estar estruturadas dentro de uma metacomunidade onde o efeito de massa pode ser o paradigma que melhor explica os padrões observados. / Coastal lagoons are dynamics ecosystems characterized by high levels of biodiversity, and they can be envisaged as discrete patches immersed in the landscape. Community patterns observed in coastal lagoons can be explained by ecological theories, such as, Island Biogeography and Metacommunity Ecology. These theories emphasize that the degree of isolation and habitat heterogeneity, in the landscape scale, are important factors defining community patterns. Our aim was to investigate the influence of these factors on different community descriptors (species composition, alpha and beta diversity) of fish communities in coastal lagoons, using landscape metrics. Our study area is located in the Tramandaí river system, RS (50,14°O; 29,98°S). This system communicates with the ocean through the Tramandaí estuary, and it encompasses 41 lagoons with different degrees of connection. We quantified landscape variables using geographic information systems (Spot and Landsat-TM5 images). These variables were grouped in two categories; structural variables (area, shape, distance to the ocean, coefficient of variation of area, primary connectivity and estuarine connectivity) and land use/land cover variables (using buffers of 50, 100, 250 and 500 m). Ichthyofauna data were obtained through standardized sampling, using gillnets and trawls in 38 lagoons. Our results show that different community descriptors respond to different landscape variables. Altogether, structural and land use/land cover variables explain 18% of the variation of fish composition (abundance) of shallow margins; while structural variables explain 7% of the total variation of fish composition inhabiting deeper banks. Both assemblages exhibit a balanced partition of variation among variables representing landscape isolation and heterogeneity. However, when considering other community descriptors, such as, alpha and beta diversity, we observed that landscape variables are more important in explaining the diversity within each lagoon (alpha), but they are not significant in predicting diversity between lagoons (beta). These results suggest that fish assemblages of coastal lagoons can be structured within a metacommunity, and that the mass effect may be the paradigm that better explains the observed patterns.
20

Influência de variáveis de paisagem sobre a riqueza e composição de assembleias de peixes em lagoas costeiras no sul do Brasil

Guimarães, Taís de Fátima Ramos January 2013 (has links)
Lagoas costeiras são ecossistemas dinâmicos caracterizados por uma alta biodiversidade, e podem ser vistos como manchas de hábitats na paisagem. Potencialmente, as características das comunidades em lagoas podem ser explicadas por teorias ecológicas (Biogeografia de Ilhas e Ecologia de Metacomunidades), onde o grau de isolamento e a heterogeneidade do hábitat em escala da paisagem são fatores importantes na determinação da comunidade. O objetivo deste trabalho foi verificar a influência destes fatores sobre diferentes descritores da comunidade (abundância, diversidade alfa e beta) de peixes em lagoas costeiras, utilizando métricas de paisagem. A área de estudo localiza-se no sistema do rio Tramandaí, RS (50,14°O; 29,98°S), possui 41 lagoas com diferentes graus de conexão e comunica-se com o mar através do estuário de Tramandaí. As variáveis de paisagem foram obtidas através de sistemas de informação geográfica (imagens Spot e Landsat-TM5) e foram divididas entre variáveis estruturais (área, forma, distância do mar, coeficiente de variação da área, conectividade primária e conectividade estuarina) e variáveis de uso e cobertura da terra (buffer de 50, 100, 250 e 500 m). Dados de ictiofauna foram obtidos através de amostragem padronizada com rede de espera e de arrasto em 38 lagoas. Nossos resultados mostram que diferentes descritores da comunidade respondem a diferentes variáveis de paisagem. Quando considerada a composição de assembleias que habitam diferentes porções do corpo d’água observamos que 18% da variação nas assembleias de margens rasas são explicadas pelas variáveis estruturais e de uso e cobertura; já assembleias que habitam margens mais profundas respondem apenas as variáveis estruturais, as quais explicam 7% da variação nessa assembleia. Ambas as assembleias possuem partição de variância equilibrada entre variáveis que representam o isolamento e a heterogeneidade da paisagem. No entanto, quando consideramos outros descritores da comunidade como diversidade alfa e beta, observamos que as variáveis estruturais e de uso e cobertura da terra são mais importantes para explicar a diversidade dentro do corpo d’água (alfa), não sendo significantes para predizer a diversidade entre corpos d’água (beta). Esses resultados nos sugerem que as assembleias de peixes de lagoas costeiras podem estar estruturadas dentro de uma metacomunidade onde o efeito de massa pode ser o paradigma que melhor explica os padrões observados. / Coastal lagoons are dynamics ecosystems characterized by high levels of biodiversity, and they can be envisaged as discrete patches immersed in the landscape. Community patterns observed in coastal lagoons can be explained by ecological theories, such as, Island Biogeography and Metacommunity Ecology. These theories emphasize that the degree of isolation and habitat heterogeneity, in the landscape scale, are important factors defining community patterns. Our aim was to investigate the influence of these factors on different community descriptors (species composition, alpha and beta diversity) of fish communities in coastal lagoons, using landscape metrics. Our study area is located in the Tramandaí river system, RS (50,14°O; 29,98°S). This system communicates with the ocean through the Tramandaí estuary, and it encompasses 41 lagoons with different degrees of connection. We quantified landscape variables using geographic information systems (Spot and Landsat-TM5 images). These variables were grouped in two categories; structural variables (area, shape, distance to the ocean, coefficient of variation of area, primary connectivity and estuarine connectivity) and land use/land cover variables (using buffers of 50, 100, 250 and 500 m). Ichthyofauna data were obtained through standardized sampling, using gillnets and trawls in 38 lagoons. Our results show that different community descriptors respond to different landscape variables. Altogether, structural and land use/land cover variables explain 18% of the variation of fish composition (abundance) of shallow margins; while structural variables explain 7% of the total variation of fish composition inhabiting deeper banks. Both assemblages exhibit a balanced partition of variation among variables representing landscape isolation and heterogeneity. However, when considering other community descriptors, such as, alpha and beta diversity, we observed that landscape variables are more important in explaining the diversity within each lagoon (alpha), but they are not significant in predicting diversity between lagoons (beta). These results suggest that fish assemblages of coastal lagoons can be structured within a metacommunity, and that the mass effect may be the paradigm that better explains the observed patterns.

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