550 resultados para Upland buzzard ( Buteo hemilasius)
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A pollen profile from the highest known peatbog in the Alps is presented. The peatbog started to grow about 8000 years ago and over the last 5000 years. The influence of man on the vegetation is documented. Before the beginning of the bronze age pasturing started.
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Determining the manner in which food webs will respond to environmental changes is difficult because the relative importance of top-down vs. bottom-up forces in controlling ecosystems is still debated. This is especially true in the Arctic tundra where, despite relatively simple food webs, it is still unclear which forces dominate in this ecosystem. Our primary goal was to assess the extent to which a tundra food web was dominated by plant-herbivore or predator--rey interactions. Based on a 17-year (1993-2009) study of terrestrial wildlife on Bylot Island, Nunavut, Canada, we developed trophic mass balance models to address this question. Snow Geese were the dominant herbivores in this ecosystem, followed by two sympatric lemming species (brown and collared lemmings). Arctic foxes, weasels, and several species of birds of prey were the dominant predators. Results of our trophic models encompassing 19 functional groups showed that <10% of the annual primary production was consumed by herbivores in most years despite the presence of a large Snow Goose colony, but that 20-100% of the annual herbivore production was consumed by predators. The impact of herbivores on vegetation has also weakened over time, probably due to an increase in primary production. The impact of predators was highest on lemmings, intermediate on passerines, and lowest on geese and shorebirds, but it varied with lemming abundance. Predation of collared lemmings exceeded production in most years and may explain why this species remained at low density. In contrast, the predation rate on brown lemmings varied with prey density and may have contributed to the high-amplitude, periodic fluctuations in the abundance of this species. Our analysis provided little evidence that herbivores are limited by primary production on Bylot Island. In contrast, we measured strong predator-prey interactions, which supports the hypothesis that this food web is primarily controlled by top-down forces. The presence of allochthonous resources subsidizing top predators and the absence of large herbivores may partly explain the predominant role of predation in this low-productivity ecosystem.
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Mode of access: Internet.
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First published in 1911; this edition adds an afterword.
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Includes index and bibliographical references.
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Mode of access: Internet.
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"Summary of ... commodity loan and payment program."
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Publisher's advertisement: [1] p. at end.
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Pages [19]-36 contain: "The Great Law, or, The body of laws of ye province of Pennsylvania and territorys thereunto belonging, past at an assembly at Chester, als. Upland, the seventh day of ye tenth month, December, 1682." Corrections in capitalization have been made in a contemporary hand.
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Mode of access: Internet.
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- Stories of plot. (a) Dramatic incident:The red mark, John Russell. The Chink and the child, Thomas Burke. (b) Detective and mystery: The Doomdorf mystery, Melville Davisson Post. (c) Ingenuity and surprise: How it happened, A. Conan Doyle. (D) Problem: A jury of her peers, Susan Glaspell.- Stories of character. (a) Individual: Humoresque, Fannie Hurst. The game of life and death, Lincoln Colcord. (b) Psychological: The belled buzzard, Irvin Cobb.- Stories of setting. (a) Local color: The conversion of Elviny...
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"April 2000."