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Research Article

Are protected areas really protecting populations? A test with an Atlantic rain forest palm [ 361-372 ]

Rita de Cássia Quitete Portela, Emilio M. Bruna and Flavio Antonio Maës dos Santos

Abstract
We compared the demography of the palm Euterpe edulis in a large forest fragment that is protected from palm harvesting with that in three smaller fragments where harvesting has occurred. Palms were censused from 2005 to 2007 in nine 30 m x 30 m plots in each forest fragment. Each individual was assigned to one of five stage classes: seedling, infant, juvenile, immature, and reproductive. Using summary matrices constructed for the fragments and a matrix for the population in the protected area, we compared the asymptotic growth rate (λ) in the protected and non-protected areas. We then quantified the contribution of each lower-level vital rate to the observed differences in λ using a fixed-design LTRE. Euterpe edulis populations in the protected area are projected to shrink at rates of 4.54 to 12.6% per year, and the populations of the fragments are projected to grow at rates of 3.44 to 9.43% per year. Our LTRE analysis revealed that the generally higher λ for the summary matrix based on the populations in fragments was due primarily to greater survival of immatures and reproductives. However, seedling growth contributed negatively to λ in the fragments. We also found that great numbers of immatures and reproductives were killed by the capuchin monkey (Cebus nigritus), which apparently also contributes to the differences between the protected area and the fragments. This study lends support to the idea that small fragments in a landscape actively managed and modified by humans can be very important in maintaining viable plant populations.


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    English: We compared the demography of the palm Euterpe edulis in a large forest fragment that is protected from palm harvesting with that in three smaller fragments where harvesting has occurred. Palms were censused from 2005 to 2007 in nine 30 m x 30 m plots in each forest fragment. Each individual was assigned to one of five stage classes: seedling, infant, juvenile, immature, and reproductive. Using summary matrices constructed for the fragments and a matrix for the population in the protected area, we compared the asymptotic growth rate (λ) in the protected and nonprotected areas. We then quantified the contribution of each lower-level vital rate to the observed differences in λ using a fixed-design LTRE. Euterpe edulis populations in the protected area are projected to shrink at rates of 4.54 to 12.6% per year, and the populations of the fragments are projected to grow at rates of 3.44 to 9.43% per year. Our LTRE analysis revealed that the generally higher λ for the summary matrix based on the populations in fragments was due primarily to greater survival of immatures and reproductives. However, seedling growth contributed negatively to λ in the fragments. We also found that great numbers of immatures and reproductives were killed by the capuchin monkey (Cebus nigritus), which apparently also contributes to the differences between the protected area and the fragments. This study lends support to the idea that small fragments in a landscape actively managed and modified by humans can be very important in maintaining viable plant populations.

    Español: En este estudio comparamos la demografia de la palma Euterpe edulis en un fragmento de selva grande y protegido de la cosecha de las hojas de esta palma con la población de la palma en tres fragmentos pequeños en donde la cosecha se presenta de modo regular. Los resultados indican que existe una mayor supervivencia de individuos inmaduros y reproductivos en los fragmentos, ya que muchos de estos son matados por las actividades forrajeras de monos capuchinos en el fragmento grande y protegido. Asi, el estudio sugiere que los fragmentos pequeños en el paisaje pueden ser importantes en el mantenimiento de poblaciones viables de la palma, siempre y cuando sean manejados activamente por humanos.

    Portugués: Comparamos a demografia da palmeira Euterpe edulis em um grande fragmento florestal protegido da extração de palmito com a de três fragmentos pequenos onde já ocorreu extração. Entre 2005 e 2007, as palmeiras foram amostradas em nove parcelas de 30 m x 30 m em cada fragmento florestal. Cada indivíduo foi identificado como uma das cinco classes: plântula, infante, juvenil, imaturo e reprodutivo. Usamos matrizes “summary” construídas para os fragmentos e uma matriz para a população da área protegida. Com esses dados, comparamos a taxa de crescimento assintótico (λ) da área protegida com a das áreas não-protegidas. Em seguida, quantificamos a contribuição de cada taxa vital básica para as diferenças observadas no λ por meio de um LTRE com desenho fixo. Calcula-se que a população Euterpe edulis na área protegida sofrerá diminuição de tamanho de 4,54% a 12,60% ao ano, e que as populações dos fragmentos vão crescer de 3,44% a 9,43% ao ano. A análise do LTRE revelou que o λ da matriz “summary” das populações dos fragmentos foi, de modo geral, mais elevado por causa, principalmente, da maior sobrevivência de imaturos e reprodutivos. Entretanto, o crescimento das plântulas contribuiu de maneira negativa para o λ nos fragmentos. Além disso, constatamos que um grande número de imaturos e reprodutivos foram predados por macacos pregos (Cebus nigritus), o que aparentemente também contribuiu para as diferenças entre a área protegida e os fragmentos. Este estudo apóia a idéia de que fragmentos pequenos em uma paisagem muito manejada e modificada pelo homem pode ser muito importante para a manutenção de populações de plantas viáveis.
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   Tropical Conservation Science is an open-access e-journal that publishes research relating to conservation of tropical forests and other tropical ecosystems.

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