نتایج جستجو برای: forest fragmentation

تعداد نتایج: 139402  

2003
W. Chris Funk L. Scott Mills

Forest fragmentation results in population declines and extinctions for many forest vertebrates, but little is known about the mechanisms causing declines in fragments. We investigated potential causes of declines in forest fragments for an Amazonian forest frog (Colostethus stepheni) at an experimental fragmentation study site in central Amazonian Brazil using field estimates of abundance and ...

2013
Andrés Viña Jaime Estévez

The conversion of tropical forest ecosystems to agro-pastoral ecosystems and other land uses continues unabated in Latin America. The present document constitutes a comparative study in which the degree of forest fragmentation through a 23-year period (between 1973 and 1996) was evaluated in two areas located within the same ecological region, but in two different countries (Colombia and Ecuado...

2010
Robert C. Harriss David L. Skole G. Arturo Sánchez-Azofeifa

Accurate estimates of forest cover and forest fragmentation are critical for developing countries such as Costa Rica, which holds four to five percent of the world’s plant and bird species. We estimated forest cover for Costa Rica using Landsat 5 Thematic Mapper satellite scenes acquired between 1986 and 1991. In 1991, 29 percent (ca 14,000 km2) of the land cover of Costa Rica was closed forest...

2017
Isabel M D Rosa Cristina Gabriel Joāo M B Carreiras

The Brazilian Amazon in the past decades has been suffering severe landscape alteration, mainly due to anthropogenic activities, such as road building and land clearing for agriculture. Using a high-resolution time series of land cover maps (classified as mature forest, non-forest, secondary forest) spanning from 1984 through 2011, and four uncorrelated fragmentation metrics (edge density, clum...

2005
PENN LLOYD THOMAS E. MARTIN ROLAND L. REDMOND UTE LANGNER MELISSA M. HART

Forest fragmentation may cause increased brood parasitism and nest predation of breeding birds. In North America, nest parasitism and predation are expected to increase closer to forest edges because the brood-parasitic Brown-headed Cowbird (Molothrus ater) and generalist nest predators often enter the forest from adjoining developed (largely agricultural) habitats. Yet the abundance of brood p...

Journal: :Molecular ecology 2008
Stephen F Spear Andrew Storfer

Habitat loss and fragmentation are the leading causes of species' declines and extinctions. A key component of studying population response to habitat alteration is to understand how fragmentation affects population connectivity in disturbed landscapes. We used landscape genetic analyses to determine how habitat fragmentation due to timber harvest affects genetic population connectivity of the ...

Journal: :J. Geographic Information System 2011
T. V. Ramachandra Uttam Kumar

Land cover (LC) and land use (LU) dynamics induced by human and natural processes play a major role in global as well as regional patterns of landscapes influencing biodiversity, hydrology, ecology and climate. Changes in LC features resulting in forest fragmentations have posed direct threats to biodiversity, endangering the sustainability of ecological goods and services. Habitat fragmentatio...

2017
Pablo Cuenca Cristian Echeverria

Most protected areas (PA) try to limit logging of forests by means of restrictions on access and use, especially in areas where local communities coexist with the forests and depend on resources derived from PAs. In such contexts, achieving full or effective protection of the forests is almost impossible. This fact has led to researching beyond PAs boundaries in order to examine large surroundi...

2015
Wesley Dáttilo Armando Aguirre Mauricio Quesada Rodolfo Dirzo

Despite increasing knowledge about the effects of habitat loss on pollinators in natural landscapes, information is very limited regarding the underlying mechanisms of forest fragmentation affecting plant-pollinator interactions in such landscapes. Here, we used a network approach to describe the effects of forest fragmentation on the patterns of interactions involving the understory dominant p...

Journal: :محیط شناسی 0
لعبت زبردست دانشجوی دکتری برنامه ریزی محیط زیست، دانشکدة محیط زیست، دانشگاه تهران احمدرضا یاوری استادیار دانشکده محیط زیست دانشگاه تهران(ارزیابی و اکولوژی کوهستان) اسماعیل صالحی گروه مدیریت و برنامه ریزی دانشکدة محیط زیست دانشگاه تهران، دکتری شهرسازی مجید مخدوم استاد محیط زیست دانشکدة منابع طبیعی، دانشگاه تهران

fragmentation is one of the major spatial processes leading to change in a landscape, which is described as transformation of a specific habitat or land cover to smaller patches with less connectivity and viability. construction of roads is one of the main causes of fragmentation in natural areas and habitats. presence of roads in ecologically sensitive and protected areas, leads to destruction...

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