Les écosystèmes littoraux lacustres, ou ceintures des lacs, ont une valeur écologique très importante. Zones de transition et d'échanges entre les écosystèmes terrestre et aquatique, les rives des lacs et leurs zones littorales sont reconnues pour abriter une forte biodiversité, dont des plantes aquatiques visibles à l'œil nu : les macrophytes. La structure spatiale, l'abondance et la composition spécifique de ces peuplements végétaux sont conditionnées par le caractère et le fonctionnement physiques des biotopes littoraux lacustres. Ce travail de thèse est dédié à l'acquisition de connaissances sur les relations entre les peuplements macrophytiques et les déterminants physiques de biotopes littoraux lacustres dans les lacs peu profonds. Il s'applique à définir, à différentes échelles, les préférences hydroécologiques et la structure fonctionnelle et spatiale de communautés et populations de plantes aquatiques. Cette recherche s'appuie sur la modélisation et sur des observations, mesures et prélèvements menés in situ sur les macrophytes et les variables environnementales dans les grands lacs naturels du littoral aquitain. Les principaux résultats indiquent que l'action du vent et des vagues, la pente des rives, la profondeur, la granulométrie et la matière organique des sédiments influencent l'organisation spatiale et les assemblages d'espèces de macrophytes. Ces variables peuvent être utilisées pour prédire la distribution potentielle de certaines communautés végétales. Les altérations anthropiques de l'hydromorphologie favorisent le développement des espèces exotiques tout en compromettant le maintien des espèces indigènes patrimoniales. Les enjeux liés à la gestion des espèces exotiques et des espèces indigènes ont également été identifiés à partir d'une analyse diachronique des dynamiques écologiques de la végétation depuis quarante ans dans les lacs aquitains. Il est désormais urgent d'établir une stratégie de conservation des espèces indigènes, voire de restauration pour les patrimoniales, et de limiter la dispersion des espèces exotiques dans les lacs. Présentant de nombreuses analogies avec les lacs d'Europe du Nord tels que les softwater lakes ou les Lobelia lakes, les processus écologiques en cours dans les lacs du sud-ouest de la France pourraient préfigurer la situation à venir pour l'ensemble des lacs du même type dans le contexte du changement global. Les écosystèmes littoraux lacustres concentrent des enjeux écologiques, économiques et sociétaux, soulevant des questions et problématiques scientifiques sur leur fonctionnement et sur la bioindication de leur état écologique qu'il est nécessaire de continuer à explorer. / Lakeshores zones are of very high ecological value. As they are ecotones between terrestrial and aquatic ecosystems, lake shoreline and littoral zones are characterized by a high level of biodiversity, including macroscopic aquatic plants known as macrophytes. Plant distribution, abundance and species composition are determined by physical features of lakeshores. This work aims to assess relationships between macrophyte populations and communities and hydromorphological components in shallow lakes at different scales. Plant and environmental variables were modeled or collected on the field in large lakes located along the western French Atlantic coast. Wind and wave action, slope, depth, sediment grain size and organic matter content are well known for their influence on macrophyte species distribution and assemblages. Physical variables can be used to predict the potential distribution of plant communities. Anthropogenic physical disturbances enhances the development of invasive species while they threaten rare and endangered native species. Plant management issues were also highlighted from a long-term field data (fourty years) analysis of macrophyte dynamics in these shallow lakes. Management strategies are needed for the conservation of native species, or even their restoration, and the control of alien species spread in these lakes. Similar in some ways to northern European lakes such as softwater lakes or Lobelia lakes, the ecological processes identified in these Atlantic shallow lakes could foreshadow the future situation for all lakes of the same type in the context of global change. Lakeshore ecosystems gather ecological, economic and societal issues, raising scientific questions and issues about their functioning and the bioindication of their ecological status that needs to be further explored.

Les formes de croissance végétales ont fait l'objet de nombreuses études mais elles constituent encore aujourd'hui un ensemble mal défini et sans cesse remis en question en raison de l'incohérence et de l'hétérogénéité des méthodes employées pour les analyser. Cette imprécision a des répercussions négatives lorsque les formes de croissance sont utilisées dans l'étude des communautés végétales et de leur dynamique. Nous avons tenté de remédier partiellement à cette situation en appliquant à certaines d'entre elles la méthode d'analyse architecturale initiée par Hallé et Oldeman dont l'efficacité s'est avérée remarquable pour la compréhension des formes arborescentes.L'étude était destinée 1) à interpréter ces formes de croissance et leur variabilité à l'aide des concepts architecturaux, 2) à suivre les changements des traits architecturaux au sein d'une communauté végétale se développant sur des talus, lors d'une chronoséquence et en fonction de différents gradients environnementaux. Nos observations montrent que 1) les concepts et les traits architecturaux sont applicables aux formes de croissance herbacées, suffrutescentes, et buissonnantes, 2) l'expression de la réitération est la source principale de variation structurale des formes de croissance aussi bien à l'échelle spécifique qu'infra-spécifique, 3) la valeur des traits architecturaux change au cours de la succession au sein de la communauté : les plantes vivant sur des talus jeunes ont une unité architecturale simple et réitèrent à la base alors que celles croissant sur des talus plus anciens ont des unités architecturales complexes et réitèrent de manière acrotone.Ces résultats nous conduisent à discuter de la valeur holistique de la méthode d'analyse architecturale pour la caractérisation des formes de croissance, des processus biologiques permettant de passer d'une forme de croissance à une autre et de l'intérêt pratique de l'utilisation des traits architecturaux dans l'étude des communautés végétales. / The growth forms of plant have been studied many times but they still represent nowadays a fuzzy set, often modified because of the inconsistency and the heterogeneity of the methods used in their analysis. This lack of precision often leads to an inconsistency of the use of the growth forms as a trait in the studies of plants communities and their dynamics. We tried to remedy this situation by applying to some of them the architectural analysis initiated by Hallé and Oldeman, which has been relevant for the understanding of the tree growth form.This study aimed to 1) interpret these growth forms and their variability by means of architectural concepts, 2) study architectural traits variation within roadsides plants communities during succession and in a mowing context. Our resultats show that 1) the architectural concepts and traits are applicable to herbaceous, treelet and bush grosth forms, 2) the expression of the reiteration is the main source of structural variation of growth forms at specific and intraspecific levels and 3) that traits values are changing during succession within the communities : Plants living at early successionnal stages got a simple architectural unit and reiterate at the base of the individual while plants living at late successional stages got complex architectural unit and acrotonic reiteration.These resultats lead us to discuss the holistic value of the architectural analysis for growth forms charaterisation, of biological processes allowing for growth form variation and the interest of the use of architectural traits in plant communities studies.

Orientador: Flavio Antonio Maës dos Santos / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-17T22:02:12Z (GMT). No. of bitstreams: 1 Correa_ChristianeErondina_D.pdf: 5936327 bytes, checksum: 06835275c2d435b9e58c2c5894d02a54 (MD5) Previous issue date: 2011 / Resumo: Os habitats variam entre si quanta às características abióticas como luminosidade e topografia. A variação altitudinal pode conter essas diferenças e influenciar variações em escala individual e populacional das espécies. 0 objetivo geral desse trabalho foi descrever as características da espécie em escala do indivíduo, o padrão espacial e a dinâmica populacional do arbusto Psychotria nuda (Rubiaceae). Adicionalmente, verifica se há variação dessas características populacionais entre altitudes e dentro de cada altitude, considerando variações da topografia e luminosidade. 0 estudo foi realizado em Floresta Ombrófila Densa, no Parque Estadual da Serra do Mar em diferentes altitudes (Floresta de Restinga, Terras Baixas, Sub-Montana e Montana). Foram identificadas duas formas de crescimento, ereta e prostrada. lndivíduos prostrados podem apresentar crescimento clonal, encontrado em mais de 70% dos casas. 0 comprimento, o diâmetro, a área de copa e o módulo de elasticidade dos indivíduos eretos foram maiores comparados aos prostrados. Mais de 80% dos indivíduos amostrados ocorreram nas parcelas Terras Baixas. 0 comprimento foi semelhante entre altitudes, mas o diâmetro e a área da copa foram maiores nos indivíduos da Sub-Montana. A variação dos indivíduos localizados na Sub-Montana foi menor comparado aos indivíduos nas Terras Baixas. 0 padrão espacial diferiu entre as altitudes. Na Sub-Montana e na Restinga a distribuição foi agregada à pequenas distâncias e na Terras Baixas foi aleatória. Para todas as altitudes não houve variação temporal do padrão espacial. Mesmo avaliando a distribuição dos indivíduos por tamanho ou forma de crescimento, as variações influenciadas pela altitude foram preponderantes. A distribuição da densidade dos indivíduos não esteve relacionada a variações da topografia e luminosidade. 0 crescimento individual variou pouco ao Iongo do tempo e entre altitudes. Não houve variação da taxa de crescimento decamétrico com as classes de diâmetro dos indivíduos. As taxas de crescimento decamétrico não estavam relacionadas as variáveis abióticas. A taxa de crescimento populacional foi positiva, próxima a 1, nas duas altitudes. As taxas de mortalidade e de recrutamento foram muito semelhantes entre altitudes e não variaram temporal ou espacialmente. Indivíduos menores são mais freqüentes nas populações estudadas e a probabilidade de reprodução esteve associada ao tamanho do indivíduo. A maior proporção indivíduos reprodutivos na população foi encontrada na Sub-Montana. A maioria dos indivíduos permaneceu na classe de diâmetro inicial. Houve casos de regressão em até duas classes de diâmetro que podem significar a diminuição de tamanho ou fragmentação de rametas. O ingresso por reprodução sexuada foi pequeno sendo a maior parte dos recrutas originados por propagação vegetativa (91,6%). As duas altitudes diferiram quanto as contribuições para as diferenças encontradas no ?a, indicando que diferentes transições são importantes em cada hábitat. Algumas características populacionais estudadas variaram mais fortemente com a altitude em comparação a outros. As diferenças destacam que as populações das duas altitudes mantiveram estabilidade, entretanto a partir de estratégias diferentes. Na altitude maior os indivíduos foram maiores e apenas indivíduos grandes foram reprodutivos. Na altitude menor os indivíduos iniciam a reprodução com tamanho menor e ocorre maior entrada de indivíduos por propagação vegetativa / Abstract: The habitats may differ among themselves by abiotic traits like light and slope. The altitudinal variation may include these differences and influence changes in species on both individual and populational scales. The goals of this work were to describe individual traits, spatial pattern and population dynamic of shrub Psychotria nuda. Besides verify if there were variations of these population traits between altitudes and in each altitude considering slope and canopy openness variations. We developed this work in Dense-Ombrophylous Forest of Serra do Mar State Park in distinct altitudes. Two growth forms were recognized, erect and prostrate. The prostrate growth form includes the plants derived from clonal growth which is present in more than 70% of recorded individuals. The length, diameter, crown area and elastic modulus of erect growth form were higher than the prostrate one. More than 80% of the individuals occurred in the Lowland Secondary-Dense-Ombrophylous Forest. The length was similar between altitudes, but the diameter and crown area were higher in SM. Plants variations were smaller in Submontane Secondary-Dense-Ombrophylous Forest plots than in Lowland Secondary-Dense-Ombrophylous Forest. In Submontane Secondary­ Dense-Ombrophylous Forest and Coastal Plain Forest the distribution were aggregate to small distances and in Lowland Secondary-Dense-Ombrophylous Forest was random. There was no variation for all altitudes over time. Even evaluated the individuals distribution by size or growth form, the variations was mainly influenced by altitude. Individuals' density distribution was not related with slope and canopy openness variations. The individual growth of Psychotria nuda varies little over time and between altitudes. The diameter growth rate did not vary with individual's diameter class and with abiotic traits. Growth rate was positive and equals to one in both altitudes. Mortality and recruitment were similar between altitudes and did not vary in time and space. The smaller diameter classes were the most frequent ones and the reproduction probability was related with plant size. The proportion of reproductive plants was higher in Submontane Secondary-Dense-Ombrophylous Forest. Most plants remained in the original diameter class. There were some cases with regression of up to two diameter classes that may mean size reduction or ramets fragmentation. There was a little input of recruits from sexual reproduction. Almost all recruits came from vegetative propagation (91,6%). The contributions to variability in ? were different between altitudes due to distinct important transitions in each altitude. Some population traits varied more strongly with altitude than others. The differences highlight that two altitudes populations maintained stability, but from different strategies. At higher altitude, plants were larger than those on lower altitude and just the bigger ones were reproductive. At lower altitude plants start reproduction earlier than in higher altitude and had more input of recruits from vegetative propagation. / Doutorado / Ecologia / Doutor em Ecologia