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Riqueza, densidade e condição física de micromamíferos numa plantação de eucaliptos
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Os eucaliptais constituem atualmente a maior área florestal em Portugal, cuja extensão tem vindo a aumentar nos últimos anos, superando já as florestas autóctones. Este aumento pode originar impactes negativos para a biodiversidade local.
De uma forma geral, este estudo pretende analisar o impacte do eucaliptal em comunidades de micromamíferos, em duas épocas do seu ciclo de vida (pré e pós-reprodução) e a diferentes níveis: riqueza específica, densidade e condição física. Deste modo efetuaram-se campanhas de armadilhagem num total de 18 pontos de amostragem, em duas áreas distintas (plantações de eucalipto e montado) com diferentes estruturas de vegetação. Em cada ponto foram registadas as espécies capturadas e os seus parâmetros populacionais, tais como: métricas corporais, carga parasitária e parâmetros de urina.
Na primeira época de amostragem foram encontradas quatro espécies diferentes de micromamíferos, sendo uma delas (Microtus cabrerae) considerada “Vulnerável” em Portugal. Contudo, na segunda época, tanto o número de espécies como de indivíduos capturados diminuiu.
De forma a determinar as variáveis envolvidas nas alterações da densidade dos micromamíferos, foram usados Modelos Lineares Generalizados Mistos (GLMM). Estes modelos revelaram que, o eucaliptal como variável habitat, não influencia negativamente a densidade total de micromamíferos, não podendo o mesmo ser afirmado para os resultados das restantes densidades calculadas. As variáveis relevantes nos cálculos das densidades são: a percentagem média de subcoberto arbustivo, a distância a outros habitats e a época de amostragem.
Os resultados da condição física dos micromamíferos revelaram, que tanto a nível da condição corporal como dos parâmetros urinários, o eucaliptal não produz um impacte negativo. Porém, na carga parasitária, este afeta positivamente, evidenciando um maior número de ectoparasitas nos micromamíferos deste habitat.
Através deste trabalho constata-se a existência de algumas espécies de micromamíferos no eucaliptal, bem como a ausência de impactes negativos significativos deste habitat nas mesmas, revelando assim a sua possível importância como habitat.
Eucalyptus plantations today represent the largest fraction of forested areas in Portugal, and its extension has increase over the last years, exceeding that of native forests. This change in the landscape is perceived has negatively impacting local biodiversity. In a general way, this study aimed to analyze the effect of eucalyptus plantations on the small mammal community considering two different periods of their life cycle (pre and post-reproduction) and at different levels: species richness, density and physical condition. In this way, for this analysis, were made trapping campaigns, with 18 sampling points in two distinct areas (eucalyptus plantations and cork oak woodlands as a control) with different vegetation structures. At each point we registered the captured species and their population parameters, such as: body metrics, parasitic load and urine parameters. In the first sampling time, we found four different species of small mammals, were one of them (Microtus cabrerae) is considered "Vulnerable" in Portugal. However, in the second sampling time, the amount of captured animals, and the correspondent number of species have decreased. In order to determine the variables involved in the changes in the density of the small mammals, were used Generalized Linear Mixed Models (GLMM). These models revealed that there is no negative impact from eucalyptus plantations on the overall density of the small mammals, although affecting negatively the other calculated densities. The average percentage of shrub understorey, the distance to other habitats and collection time are the variables that influence the densities calculation. The small mammal’s physical conditions results, revealed that both body condition and urinary parameters, are not negatively impact by the eucalyptus plantations. However, in parasite load, this has a positive effect, indicating a higher number of ectoparasites on small mammals of this habitat. With this study we are able to confirm the existence of some species of small mammals in eucalyptus plantations, as well as the absence of significant negative impacts of this habitat on them, revealing its possible importance as habitat.
Eucalyptus plantations today represent the largest fraction of forested areas in Portugal, and its extension has increase over the last years, exceeding that of native forests. This change in the landscape is perceived has negatively impacting local biodiversity. In a general way, this study aimed to analyze the effect of eucalyptus plantations on the small mammal community considering two different periods of their life cycle (pre and post-reproduction) and at different levels: species richness, density and physical condition. In this way, for this analysis, were made trapping campaigns, with 18 sampling points in two distinct areas (eucalyptus plantations and cork oak woodlands as a control) with different vegetation structures. At each point we registered the captured species and their population parameters, such as: body metrics, parasitic load and urine parameters. In the first sampling time, we found four different species of small mammals, were one of them (Microtus cabrerae) is considered "Vulnerable" in Portugal. However, in the second sampling time, the amount of captured animals, and the correspondent number of species have decreased. In order to determine the variables involved in the changes in the density of the small mammals, were used Generalized Linear Mixed Models (GLMM). These models revealed that there is no negative impact from eucalyptus plantations on the overall density of the small mammals, although affecting negatively the other calculated densities. The average percentage of shrub understorey, the distance to other habitats and collection time are the variables that influence the densities calculation. The small mammal’s physical conditions results, revealed that both body condition and urinary parameters, are not negatively impact by the eucalyptus plantations. However, in parasite load, this has a positive effect, indicating a higher number of ectoparasites on small mammals of this habitat. With this study we are able to confirm the existence of some species of small mammals in eucalyptus plantations, as well as the absence of significant negative impacts of this habitat on them, revealing its possible importance as habitat.
Descrição
Tese de mestrado em Ecologia e Gestão Ambiental, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2015
Palavras-chave
Roedores Insetívoros Floresta de produção Mediterrâneo Portugal Teses de mestrado - 2015