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Selected Abstracts

Effects of the Surrounding Matrix on Tree Recruitment in Amazonian Forest Fragments

CONSERVATION BIOLOGY, Issue 3 2006
HENRIQUE E. M. NASCIMENTO
efectos de borde; especies pioneras; fragmentación de bosques; bosque lluvioso Abstract:,Little is known about how the surrounding modified matrix affects tree recruitment in fragmented forests. We contrasted effects of two different matrix types, Vismia - and Cecropia -dominated regrowth, on recruitment of pioneer tree species in forest fragments in central Amazonia. Our analyses were based on 22, 1-ha plots in seven experimental forest fragments ranging in size from 1 to 100 ha. By 13 to 17 years after fragmentation, the population density of pioneer trees was significantly higher in plots surrounded by Vismia regrowth than in plots surrounded by Cecropia regrowth, and the species composition and dominance of pioneers differed markedly between the two matrix types. Cecropia sciadophylla was the most abundant pioneer in fragments surrounded by Cecropia regrowth (constituting nearly 50% of all pioneer trees), whereas densities of species in Vismia -surrounded fragments were distributed more evenly. Thus the surrounding matrix had a strong influence on patterns of tree recruitment in Amazonian forest fragments. Resumen:,Se conoce poco del efecto de la matriz modificada circundante sobre el reclutamiento de árboles en bosques fragmentados. Contrastamos los efectos de dos tipos diferentes de matriz, vegetación secundaria dominada por Vismia- y Cecropia-, sobre el reclutamiento de especies de árboles pioneros en fragmentos de bosque en la Amazonía central. Nuestros análisis se basaron en 22 parcelas de 1 ha en siete fragmentos de bosque experimentales que varían entre 1 y 1000 ha. Entre 13 y 17 años después de la fragmentación, la densidad poblacional de árboles pioneros era significativamente mayor en parcelas rodeados por Vismia que en las parcelas rodeadas por Cecropia, y la composición y dominancia de especies pioneras fueron marcadamente diferentes en cada tipo de matriz. Cecropia sciadophylla fue la pionera más abundante en fragmentos rodeados por Cecropia (constituyó casi 50% de todos los árboles pioneros), mientras que las densidades de especies en los fragmentos rodeados por Vismia se distribuyeron más homogéneamente. Por lo tanto, la matriz circundante tiene una fuerte influencia sobre los patrones de reclutamiento de árboles en fragmentos de bosque Amazónicos. [source]

Experimental Assessment of Coral Reef Rehabilitation Following Blast Fishing

CONSERVATION BIOLOGY, Issue 1 2005
HELEN E. FOX
arrecifes de Indonesia; recuperación de arrecife de coral; restauración de arrecifes Abstract:,Illegal fishing with explosives has damaged coral reefs throughout Southeast Asia. In addition to killing fish and other organisms, the blasts shatter coral skeletons, leaving fields of broken rubble that shift in the current, abrading or burying new coral recruits, and thereby slowing or preventing reef recovery. Successful restoration and rehabilitation efforts can contribute to coral reef conservation. We used field experiments to assess the effectiveness of different low-cost methods for coral reef rehabilitation in Komodo National Park (KNP), Indonesia. Our experiments were conducted at three different spatial scales. At a scale of 1 × 1 m plots, we tested three different rehabilitation methods: rock piles, cement slabs, and netting pinned to the rubble. Significantly more corals per square meter grew on rocks, followed by cement, netting, and untreated rubble, although many plots were scattered by strong water current or buried by rubble after 2.5 years. To test the benefits of the most successful treatment, rocks, at more realistic scales, we established 10 × 10 m plots of rock piles at each of our nine sites in 2000. Three years after installation, coverage by hard corals on the rocks continued to increase, although rehabilitation in high current areas remained the most difficult. In 2002 rehabilitation efforts in KNP were increased over 6000 m2 to test four rock pile designs at each of four rubble field sites. Assuming that there is an adequate larval supply, using rocks for simple, low-budget, large-scale rehabilitation appears to be a viable option for restoring the structural foundation of damaged reefs. Resumen:,La pesca ilegal con explosivos ha dañado a arrecifes de coral en el sureste de Asia. Además de matar a peces y otros organismos, las explosiones destruyen esqueletos de corales, dejando campos de escombros rotos que se mueven con la corriente, erosionando o enterrando a reclutas de coral nuevos y por lo tanto disminuyen o previenen la recuperación del coral. Esfuerzos exitosos de restauración y rehabilitación pueden contribuir a la conservación de arrecifes de coral. Usamos experimentos de campo para evaluar la efectividad de diferentes métodos de bajo costo para la rehabilitación de arrecifes de coral en el Parque Nacional Komodo (PNK), Indonesia. Desarrollamos nuestros experimentos en tres escalas espaciales diferentes. A una escala de parcelas de 1 x 1 m, probamos tres métodos de rehabilitación: pilas de rocas, losas de cemento y redes sobre el escombro. Crecieron significativamente más corales por metro cuadrado sobre rocas, seguido por el cemento, redes y escombro sin tratamiento, aunque muchas parcelas fueron dispersadas por la fuerte corriente de agua o enterradas por escombros después de 2.5 años. Para probar los beneficios del tratamiento más exitoso, rocas, a escalas más realistas, en 2000 establecimos parcelas de 10 x10 m con pilas de rocas en cada unos de nuestros nueve sitios. Tres años después, la cobertura de corales duros sobre las rocas continuó incrementando, aunque la rehabilitación en áreas con corrientes fuertes fue la más difícil. En 2002, los esfuerzos de rehabilitación en PNK se incrementaron a 6000 m2 para probar cuatro diseños de pilas de rocas en cada uno de los cuatro sitios con escombros. Asumiendo que hay una adecuada existencia de larvas, la utilización de rocas para rehabilitación simple, de bajo costo y gran escala parece ser una opción viable para la restauración de la base estructural de arrecifes dañados. [source]

A Quantitative Conservation Approach for the Endangered Butterfly Maculinea alcon

CONSERVATION BIOLOGY, Issue 2 2004
MICHIEL F. WallisDeVries
The quality and size of habitat patches and their isolation from other patches are the main parameters for an assessment of population persistence, but translating persistence probabilities into practical measures is still a weak link in conservation management. I provide a quantitative conservation approach for the endangered myrmecophilous butterfly Maculinea alcon in the Netherlands. All 127 colonies known on heathland since 1990 were investigated for patch quality, size, and isolation. I assessed habitat quality in three 10 × 10 m plots for most colonies. Site occupancy in 1998,1999 was only 56%. Occupancy was best explained by a logistic regression including patch area, host ant presence, host plant abundance, overall heathland area, and connectivity between sites ( R2= 0.410, p < 0.0001); it correctly classified the occupied or vacant status for 82% of the sites. Connectivity contributed only 3.6% to the total explained variation of site occupancy, indicating that habitat characteristics were more important than isolation in determining population persistence at the examined scale level (>500 m). Grazing and sod cutting had a beneficial impact, but in combination these practices proved detrimental. Hydrological measures to prevent drainage were also associated with lowered occupancy. I used the different components in the logistic regression to formulate objective management recommendations. These consisted of sod cutting, reduction of management intensity, enlargement of habitat, or combinations of these recommendations. The results highlight the importance of careful management when site quality is determined by multiple factors. The quantitative conservation approach followed here can be fruitfully extended to other endangered species, provided enough is known about their ecological requirements and how management actions affect them. Resumen:,La preservación de fragmentos individuales es extremadamente importante para especies en peligro con capacidad de dispersión limitada. La calidad y tamaño de los fragmentos de hábitat y su aislamiento de otros fragmentos son los parámetros principales para la evaluación de la persistencia de la población, pero la traducción de probabilidades de persistencia en medidas prácticas aun es un eslabón débil en la gestión de conservación. Proporciono un método cuantitativo de conservación para la mariposa mirmecófila Maculinea alcon en peligro en Holanda. Se investigó a las 127 colonias conocidas en brezales desde 1990 para calidad, tamaño y aislamiento del fragmento. Evalué la calidad del hábitat en tres parcelas de 10 × 10 m en la mayoría de las colonias. La ocupación de sitios en 1998-1999 fue sólo 56%. La ocupación fue mejor explicada por regresión logística incluyendo la superficie del fragmento, presencia de hormigas huésped, abundancia de plantas huésped, superficie total del brezal y conectividad entre sitios ( R2= 0.410, p < 0.0001); clasificó el estatus de ocupado o vacante en 82% de los sitios. La conectividad contribuyó con solo 36% de la variación total de sitio de ocupación, lo que indica que las características de hábitat fueron más importantes que el aislamiento en la determinación de la persistencia de la población en el nivel de escala examinado (>500 m). El pastoreo y el corte de pasto tuvieron un impacto benéfico pero combinadas, estas prácticas fueron perjudiciales. Obras hidrológicas para prevenir la desecación también se asociaron con una disminución en la ocupación. Utilicé los diferentes componentes de la regresión logística para formular recomendaciones objetivas de gestión. Estas incluyeron el corte de pasto, reducción en la intensidad de manejo, aumento de hábitat o combinaciones de estas recomendaciones. Los resultados resaltan la importancia de la gestión cuidadosa cuando la calidad del sitio está determinada por múltiples factores. El método cuantitativo de preservación utilizado puede ser extendido exitosamente a otras especies en peligro, siempre que sean suficientemente conocidos sus requerimientos ecológicos y la forma en que le afectan las acciones de manejo. [source]

Cost-efficiency of Subsampling Protocols to Evaluate Oribatid-Mite Communities in an Amazonian Savanna

BIOTROPICA, Issue 6 2008
Evanira M. R. Santos
ABSTRACT Sampling oribatid mites in large areas using conventional methods is expensive, time-consuming, and this constrains their use in environmental monitoring programs. We used samples collected in 38 plots of 3.75 ha spread over 30,000 ha in an Amazonian savanna to evaluate the reduction in costs and person-hours in sampling and sorting and to elaborate cost-effective protocols. Ten samples per plot were collected and extracted using a Berlese-Tullgren apparatus. In the laboratory, samples were reduced to 50, 25, 12.5, and 6.25 percent of the initial content. Field-effort reduction was estimated by reducing the number of subsamples per plot. Dissimilarity matrices were generated using Bray,Curtis, Sørensen, and Chao,Sørensen indices. Correlations between each reduced-effort dissimilarity matrix and 100 or 50 percent sorting were used as an index of how much information was retained in reduced-effort sampling, and could still be used in multivariate analyses. The effects of most predictor variables on mite composition were detected in data based on every level of sample reduction. The intensive sampling was insufficient to reveal the full oribatid-mite fauna in the savanna; as more plots were sampled, more species were recorded. Our data indicate subsampling protocols for biodiversity assessment of oribatid mites in savanna that increase field and laboratory efficiency, and optimize both taxonomic and ecological aspects of the investigation. RESUMO A coleta de ácaros oribatídeos em grandes áreas usando métodos convencionais é dispendiosa e demorada, limitando o uso desses animais em programas de monitoramento ambiental. Foram coletados ácaros oribatídeos em 38 parcelas de 3.75 ha distribuídas sobre uma área de 30.000 ha em uma savana amazônica. Com o objetivo de elaborar protocolos simples e eficientes, foi avaliada a redução dos custos e do tempo para a coleta e a triagem desses animais. Em cada parcela foram coletadas 10 subamostras compostas, que foram extraídas com aparato de Berlese-Tullgren e reduzidas em porcentagens de 50, 25, 12.5 e 6.25 do conteúdo inicial. A diminuição do esforço do campo foi estimada pela redução do número de amostras por parcela. Análise de ordenação multidimensional foi usada para gerar matrizes de dissimilaridade. Correlações entre cada matriz de dissimilaridade do esforço reduzido e triagem de 100 ou 50 por cento foram usadas como um índice da informação mantida e que ainda poderia ser usada nas análises multivariadas. Houve o efeito da presença de arbustos sobre a composição de ácaros em dados baseados em cada nível de redução das amostras. A coleta intensiva não foi suficiente para observar a riqueza completa de espécies na savana; quanto mais parcelas eram coletadas, mais espécies foram registradas. Os dados indicam protocolos de subamostragem para inventários da biodiversidade de ácaros oribatídeos em savanas, que podem aumentar a eficiência no campo e no laboratório, além de aperfeiçoar o aspecto taxonômico e ecológico da investigação. [source]

Mesoscale Gradients of Herb Richness and Abundance in Central Amazonia,

BIOTROPICA, Issue 6 2006
Flávia R. C. Costa
ABSTRACT There are few hypotheses to explain local understory diversity patterns. There is a consensus that climate and soil fertility affect understory density and diversity at large scales, but few studies addressed the mechanisms controlling density and diversity locally. Here, I examine patterns of abundance and diversity of three understory herb groups along gradients of soil nutrients and topography at the mesoscale (64 km2) in a wet tropical forest, and possible factors causing them. Herb richness, diversity, density, and cover were measured in fifty-nine 250 × 2 m plots systematically distributed over Reserva Ducke, Manaus. Herb groups responded differently to environmental gradients. Whereas density and cover of pteridophytes increased with altitude and slope, Marantaceae density and cover decreased. Density of sedges increased with altitude, but did not vary with slope. Density and cover of Marantaceae and sedges but not pteridophytes increased with the soil cation content. Pteridophyte richness increased with slope whereas Marantaceae richness decreased, richness of both groups increased with cation content. Diversity increased with altitude for Marantaceae and decreased for pteridophytes. Some of these patterns agree with what is expected from herbs, such as the greater abundance of Marantaceae and sedges in flat and low altitude plots, where water availability is higher and probably also light, and the greater richness of Marantaceae and pteridophytes in higher nutrient plots. The unexpected results of higher abundance and richness of pteridophytes in slopes, instead of in bottomlands, suggest that biotic or litter-mediated controls may be important to set these patterns. RESUMO Existem poucas hipóteses para explicar os padrões locais de diversidade do sub-bosque. Existe consenso de que clima e fertilidade do solo afetam a densidade e diversidade do sub-bosque em macro-escala, mas poucos estudos procuraram os mecanismos que controlam a densidade e diversidade em escala local. Neste estudo, eu examino os padrões de abundância e diversidade de 3 grupos de ervas de sub-bosque ao longo de gradients de nutrientes e topografia em uma floresta tropical úmida, e os possíveis fatores causais. A riqueza, diversidade, cobertura e densidade das ervas foram medidas em 59 parcelas de 250 × 2 m, distribuídas sobre 64 km2 na Reserva Ducke, Manaus. Os grupos de ervas responderam de forma diferente aos gradientes ambientais. Enquanto a densidade e cobertura das samambaias aumentaram com a altitude e a inclinação do terreno, a densidade e cobertura de Marantaceae diminuíram. A densidade de capins aumentou coma altitude, mas não variou com a inclinação. A densidade e cobertura de Marantaceae e capins aumentou com o conteúdo de nutrientes do solo, mas não para as pteridófitas. A riqueza de samambaias aumentou com a inclinação do terreno enquanto a riqueza de Marantaceae decresceu, e a riqueza dos dois grupos aumentou com o conteúdo de nutrientes. A diversidade aumentou com a altitude para Marantaceae e diminuiu para as samambaias. Alguns destes padrões concordam com o esperado para ervas, tais como a maior abundância de Marantaceae e capins nas parcelas planas e baixas, onde a disponibilidade de água e provavelmente de luz são maiores. Entretanto, os resultados inesperados de maior abundância e riqueza de pteridófitas nos terrenos mais inclinados, ao invés de nos baixios, sugerem que controles bióticos ou mediados pela liteira podem ser mais importantes para o estabelecimento destes padrões. [source]

Landscape Heterogeneity and Diurnal Raptor Diversity in Honduras: The Role of Indigenous Shifting Cultivation,

BIOTROPICA, Issue 3 2001
David L. Anderson
ABSTRACT I studied the relationship between diurnal raptor diversity, density, and richness, and landscape heterogeneity in continuous primary forests and forests farmed by native Amerindians in the Río Plátano Biosphere Reserve of northeastern Honduras from January to June 1996 and 1997. I estimated landscape heterogeneity,the variability in naturally occurring and/or anthropogenic habitat mosaics,by mapping the extent and distribution of five human-modified and natural habitats in 24 1 km2 survey plots. I used the Shannon index to calculate landscape heterogeneity values for the respective plots based on the proportion of total area of each habitat within each plot. Diurnal raptor surveys from canopy-emergent viewpoints in these plots resulted in 137 observations of 18 species of raptors. Four species (Coragyps atratus, Ictinia plumbea, Leucopternis albicollis, and Buteo magnirostris) differed significantly in abundance among heterogeneity classes. Raptor diversity, density, and richness all increased directly with increasing landscape heterogeneity. Landscape heterogeneity was more important in explaining differences in raptor species diversity than the presence or extent of any single habitat or combination of habitats. In contrast to previous studies, my results indicate the importance of indigenous shifting cultivation in altering the naturally occurring patterns of habitat mosaics in lowland rain forest and its effect on bird species abundance and diversity in a rain forest ecosystem. RESUMES Estudié la relación entre la diversidad, densidad y la riqueza de especies de rapaces diurnas con la heterogeinidad de paisajes en bosques primaries contínues y bosques donde practican la agricultura migratoria indígenas de la Reserva de Biósfera del Río Plátano al noreste de Honduras entre los meses de enero a junio de 1996 y 1997. Evalué la heterogeneidad de paisajes-la variabilidad en mosaicos de hábitats naturales o antropogínicos-con mapas de cinco hábitats en 24 parcelas de 1 km2. Usé el Indice de Shannon para calcular valores de la heterogeneidad de cada parcela, basado en la proporción de cada hábitat. Desde el dosel, hice conteos de rapaces en las 24 parcelas que resukaron en 137 observaciones de 18 especies. Cuatro especies (Coragyps atratus, Ictinia plumbea, Leocopternis albicollis, y Buteo magnirostris) difirieron significativamente en abundancia entre los grupos de heterogeneidad del paisaje. La diversidad, densidad y riqueza de especies aumentaron conjuntamente con la heterogeneidad del paisaje. La heterogeneidad del paisaje rue mas importante para explicar la diversidad de rapaces que la presencia o el área de cualquier hábitat o combinación de hábitats. En contraste con estudios anteriores, mis resultados sugieron la importancia de la agricultura migratoria indigena en la alteracíon de mosaicos de hábitats naturales en los bosques hiimedos bajos, y su efecto en la abundancia y diversidad de aves de un ecosistema forestal. [source]