918 resultados para Tapia woodland


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The recent article by Fenton (Fenton JH. 2008. A postulated natural origin for the open landscape of upland Scotland. Plant Ecology & Diversity 1:115–127) has argued that the landscapes of upland Scotland are treeless because of long-term deterioration of soil conditions. There are reasons for thinking that this might be the case in the absence of human activity. However, there have been considerable anthropogenic pressures on these landscapes for several millenia, documented archaeologically and palaeoecologically. Attempting to exclude these pressures from the discussion can only lead to an incomplete and misleading account of a complex series of changes involving an interaction which includes natural vegetational and environmental processes, climatic changes and human pressures.

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In recent years, the native woodlands of Europe, including those of Britain and Ireland, have increasingly come under threat from a range of biotic and abiotic factors, and are therefore a conservation priority demanding careful management in order to realise their inherent ecological and cultural benefits. Because the distribution of genetic variation across populations and regions is increasingly considered an important component of woodland management, we carried out a population genetic analysis on black alder (Alnus glutinosa) across Northern Ireland in order to inform “best practice” strategies. Our findings suggest that populations harbour high levels of genetic diversity, with very little differentiation between populations. Significant F IS values were observed in over half of the populations analysed, however, which could reflect inbreeding as a result of the patchy occurrence of alder in Northern Ireland, with scattered, favourable damp habitats being largely isolated from each other by extensive tracts of farmland. Although there is no genetic evidence to support the broad-scale implementation of tree seed zones along the lines of those proposed for native woodlands in Great Britain, we suggest that the localised occurrence of rare chloroplast haplotypes should be taken into account on a case-by-case basis. This, coupled with the identification of populations containing high genetic diversity and that are broadly representative of the region as a whole, will provide a sound genetic basis for woodland management, both in alder and more generally for species that exhibit low levels of genetic differentiation.

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Hesperian College football team, Woodland, California, 1891. Standing, left to right: Sidney Elston, Ernest Norton, Charlie Elston, Charlie Merritt, Jimmie Johnston, Rolls Bray, Frank Zimmerman. Seated, left to right: John Gardner, Bill Banks, Jerry Rust, Bob Simons. On floor, left to right: Joe Harlan, George Martin.

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Hesperian College building, constructed in 1860-61, Woodland, California, ca. 1862. [Chapman University was founded by members of the Christian Church (Disciples of Christ) as Hesperian College in Woodland, Calif., on March 4, 1861. In 1920, the assets of Hesperian College were absorbed by California Christian College, which held classes in downtown Los Angeles. In 1934, the school was renamed after the chairman of its board of trustees (and primary benefactor), C.C. Chapman.]

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Hesperian College building, constructed in 1860-61, with students and faculty, Woodland, California, ca. 1862. [Chapman University was founded by members of the Christian Church (Disciples of Christ) as Hesperian College in Woodland, Calif., on March 4, 1861. In 1920, the assets of Hesperian College were absorbed by California Christian College, which held classes in downtown Los Angeles. In 1934, the school was renamed after the chairman of its board of trustees (and primary benefactor), C.C. Chapman.]