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201.
Henry N.N. Bulley James W. Merchant David B. Marx John C. Holz Aris A. Holz 《Journal of the American Water Resources Association》2007,43(3):605-621
Abstract: The U.S. Environmental Protection Agency is charged with establishing standards and criteria for assessing lake water quality. It is, however, increasingly evident that a single set of national water quality standards that do not take into account regional hydrogeologic and ecological differences will not be viable as lakes clearly have different inherent capacities to meet such standards. We demonstrate a GIS‐based watershed classification strategy for identifying groups of Nebraska reservoirs that have similar potential capacity to attain a certain level of water quality standard. A preliminary cluster analysis of 78 reservoirs was performed to determine the potential number of Nebraska reservoir groups. Subsequently, a Classification Trees method was used to refine number of classes, describe the structure of reservoir watershed classes, and to develop a predictive model that relates watershed conditions to reservoir classes. Results suggest that Nebraska reservoirs can be represented by nine classes and that soil organic matter content in the watershed is the most important single variable for segregating the reservoirs. The cross‐validation prediction error rate of the Classification Tree model was 26.3%. Because all geospatial data used in this work are available nationally, the method could be adopted throughout the U.S. Hence, this GIS‐based watershed classification approach could provide water resources managers an effective decision‐support tool in managing reservoir water quality. 相似文献
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广东科龙集团无氟生产线中的预混站是使用环戊烷危险物品配制发泡剂的重大危险源,燃烧爆炸事故风险较大。笔者针对该生产场所重大危险源,应用事故树分析方法,编制了预混站的燃烧爆炸事故树,计算出事故能量及伤害后果。通过对事故树的定性和定量分析,得出事故树的最小割集和最小径集,判定事故发生的可能途径,选定预防事故发生的最佳方案。针对导致事故发生的可能原因组合,制定有效的安全技术措施和管理制度,为国内同类企业预防该类事故提供依据。 相似文献
204.
I. P. Belousova K. A. Smirnov V. D. Kaz’min I. V. Kudrjavtsev 《Russian Journal of Ecology》2005,36(2):115-119
The forest ecosystem of the Orlovskoe Polese National Park has been studied in reference to the reintroduction of a rare species: the European bison (Bison bonasus L.). Preliminary data characterizing the state of forest resources and the populations of ungulates living in the forests, as well as the genetic problems associated with maintaining a viable population of the European bison, are considered.Translated from Ekologiya, No. 2, 2005, pp. 132–137.Original Russian Text Copyright © 2005 by Belousova, Smirnov, Kazmin, Kudrjavtsev. 相似文献
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Managing Urban Trees and Their Soil Envelopes in a Contiguously Developed City Environment 总被引:7,自引:0,他引:7
Jim CY 《Environmental management》2001,28(6):819-832
Urban Hong Kong is covered by high building, road, and population densities. Its urban morphology is inherently not conducive
to extensive or high-grade greening. Recent renewal of old areas has squeezed out some limited interstitial plantable space,
although in new development areas modest spaces have been earmarked for greenery. The study aims at evaluating the major constraints
to urban trees and their companion urban soil envelopes and at providing specific recommendations to improve tree management
in the city. The analysis covers the above-ground confinements that dampen tree performance, the less tangible but rather
difficult institutional restrictions that impose a somewhat unnecessary lid on tree planting, the multiplicity of players
and stakeholders involved in urban-tree management that militates against coordination and cooperation, the widespread occupation
of underground space by utility lines often to the exclusion of trees, and the extremely poor quality of urban soils that
are often used without amelioration to support tree growth. The management recommendations furnish practical suggestions and
hints to improve the short- and long-term welfare of trees in terms of quality, quantity, and spatial distribution. The conclusion
enumerates some concrete measures for consideration by decision-makers to upgrade the city's greenery to close the gap between
science and policy. 相似文献
207.
The presence of Whitethroats and their potential invertebrate prey in farmland trees and shrubs was investigated. The management of this vegetation by farmers, and their motivation for that management, was explored using participatory techniques. Whitethroats were associated with Guiera senegalensis, the shrub species which supports most caterpillars and spiders. Farmers reported declines in trees and shrubs since the 1950s, loss of fallow areas, declines in soil fertility and crop yields, and increases in the use of fire for clearing fields. Trees are valued by people for their cultural and medicinal uses and some species used by Whitethroats and other birds have potential for restoring soil fertility, although this was not recognised by farmers. More sustainable use of savanna farmland could have both agronomic and wider conservation benefits, and the provision of information that accommodates farmers' cultural and economic incentives could benefit both farmers and wildlife. 相似文献
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The structure of the crown and branching; the growth, development, and ontogeny of branches; and organogenesis and growth of female shoots in the model Siberian stone pine trees were studied in four types of habitats at the timberline in the central Altai Mountains (1700–2170 m a.s.l.). The results provided evidence that the ecological forms of trees appear due to changes in the pattern of branching as well as to the decreased rate of vegetative (primarily apical) growth. The diameter of the shoot pith is one of the most variable characters reflecting the deterioration of environmental conditions at higher elevations. 相似文献