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Concept
Edge effects
Résumé
In ecology, edge effects are changes in population or community structures that occur at the boundary of two or more habitats. Areas with small habitat fragments exhibit especially pronounced edge effects that may extend throughout the range. As the edge effects increase, the boundary habitat allows for greater biodiversity.
Urbanization is causing humans to continuously fragment landscapes and thus increase the edge effect. This change in landscape ecology is proving to have consequences. Generalist species, especially invasive ones, have been seen to benefit from this landscape change whilst specialist species are suffering. For example, the alpha diversity of edge-intolerant birds in Lacandona rainforest, Mexico, is decreasing as edge effects increase.
Inherent – Natural features stabilize the border location.
Induced – Transient natural disturbances (e.g., fire or flood) or human related activities, subject borders to successional changes over time.
Narrow – One habitat abruptly ends and another begins (e.g., an agricultural field.)
Wide (ecotone) – A large distance separates the borders of two clearly and purely definable habitats based upon their physical conditions and vegetation, and in between there exists a large transition region.
Convoluted – The border is non-linear.
Perforated – The border has gaps that host other habitats.
Height can create borders between patches as well.
Environmental conditions enable certain species of plants and animals to colonize habitat borders. Plants that colonize forest edges tend to be shade-intolerant. These plants also tend to be tolerant of dry conditions, such as shrubs and vines. Animals that colonize tend to be those that require two or more habitats, such as white-tailed and mule deer, elk, cottontail rabbits, blue jays, and robins. Some animals travel between habitats, while edge species are restricted to edges. Larger patches have increased native species biodiversity compared to smaller patches.
Source officielle
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