Legado da história da paisagem na estrutura das comunidades de riachos
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Data
2019-08-19
Autores
Santos, Edineusa Pereira dos
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Esta tese busca entender a estruturação de comunidades de riachos em paisagens modificadas enquanto contabiliza possíveis assincronias entre ambas. Logo, ela questiona os pressupostos de que (i) é necessário incluir características das paisagens passadas para alcançar uma abordagem mais completa dos fatores estruturadores das comunidades atuais e (ii) alternativamente, de que lapsos temporais nas respostas das comunidades devem ser considerados para compreender a total magnitude dos efeitos de uma dada mudança da paisagem. Além disso, são explorados condicionantes relacionados à caracterização do histórico da paisagem, ao tipo de descritor da comunidade e à complexidade do sistema ecológico. Em seu primeiro manuscrito, esta tese confirma tais pressupostos enquanto apresenta o primeiro registro de respostas tardias de insetos aquáticos em região tropical. Nele, eu demonstro que padrões nas comunidades poderiam ser mais bem compreendidos quando o histórico é descrito com mais de uma característica (e.g., média histórica e trajetórias de perda e ganho de cobertura florestal) e que a detecção de respostas tardias varia de acordo com os descritores de comunidades estudados. Em seu segundo manuscrito, um modelo teórico foi testado admitindo múltiplas relações simultâneas e, predominantemente, indiretas para o sistema de estudo. Neste, além daqueles pressupostos, foram confirmados caminhos causais pelos quais a cobertura florestal e usos dos solos estruturam as comunidades. Com os caminhos são fornecidas evidências empíricas de que a montagem das comunidades de insetos aquáticos é afetada pela quantidade de floresta remanescente através da regulação das condições ambientais locais dos riachos e pelo arranjo recente e pretérito dos fragmentos florestais conforme sua influência sobre a conectividade espacial ao longo dos riachos. Assim, além de acrescentar elementos à ecologia de comunidades e à interpretação de distúrbios antropogênicos, tais achados abrem uma janela de oportunidade para tomadores de decisão. Pois, de um lado, eles assinalam a possibilidade para interromper futura perda de espécies decorrente de modificação recente da paisagem em sistemas fluviais e, de outro, alertam para a influência do histórico das paisagens para o sucesso de atividades de restauração.
This thesis aims to understand the assembly of stream communities in modified landscapes by accounting for possible asynchronies between the two. In this way, it questions the assumptions that (i) it is necessary to include past landscape characteristics to reach a more complete approach of the structuring factors of current communities, and that (ii), alternatively, one should consider time lags in community responses to encompass the magnitude of the effects of a certain landscape change. In addition, drivers related to the characteristics of landscape history, the type of community descriptor and the complexity of the ecological system are questioned. In its first manuscript, this thesis confirms those assumptions and shows the first record of delayed responses of aquatic insects in the tropical region. In that, I show that patterns in communities could be better understood when landscape history is described with more than one characteristic (e.g., historical mean and loss and gain trajectories of forest cover) and that the detection of delayed responses varies according to the community descriptors. In its second manuscript, a theoretical model was tested admitting multiple simultaneous, and predominantly, indirect relationships in the study system. Then, in addition to the previous assumptions, causal pathways by which forest cover and land uses structure communities were confirmed. With the paths, empirical evidence that aquatic insect community assembling is affected by the amount of forest remaining via instream condition regulation and by the arrangement of the recent and past forest fragments according to their influence on the connectivity along the channels were provided. Thus, in addition to including elements to community ecology and the interpretation of anthropogenic disturbances, such findings open a window of opportunity for decision makers. Because, in a way, they indicate the possibility of interrupting future species loss due to recent landscape modification in river systems and, in another one, they alert to influence of landscape history on the success of restoration activities.
This thesis aims to understand the assembly of stream communities in modified landscapes by accounting for possible asynchronies between the two. In this way, it questions the assumptions that (i) it is necessary to include past landscape characteristics to reach a more complete approach of the structuring factors of current communities, and that (ii), alternatively, one should consider time lags in community responses to encompass the magnitude of the effects of a certain landscape change. In addition, drivers related to the characteristics of landscape history, the type of community descriptor and the complexity of the ecological system are questioned. In its first manuscript, this thesis confirms those assumptions and shows the first record of delayed responses of aquatic insects in the tropical region. In that, I show that patterns in communities could be better understood when landscape history is described with more than one characteristic (e.g., historical mean and loss and gain trajectories of forest cover) and that the detection of delayed responses varies according to the community descriptors. In its second manuscript, a theoretical model was tested admitting multiple simultaneous, and predominantly, indirect relationships in the study system. Then, in addition to the previous assumptions, causal pathways by which forest cover and land uses structure communities were confirmed. With the paths, empirical evidence that aquatic insect community assembling is affected by the amount of forest remaining via instream condition regulation and by the arrangement of the recent and past forest fragments according to their influence on the connectivity along the channels were provided. Thus, in addition to including elements to community ecology and the interpretation of anthropogenic disturbances, such findings open a window of opportunity for decision makers. Because, in a way, they indicate the possibility of interrupting future species loss due to recent landscape modification in river systems and, in another one, they alert to influence of landscape history on the success of restoration activities.
Descrição
Palavras-chave
Conectividade, Crédito de imigração, Débito de extinção, Equações estruturais, Filtros ambientais, Insetos aquáticos, Lapso temporal, Usos do solo, Connectivity, Immigration credit, Extinction debt, Structural equation model, Environmental filter, Aquatic insect, Time lag, Land use