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951.
Mike Bonell 《Journal of the American Water Resources Association》1998,34(4):765-785
ABSTRACT: When faced with practical forest land management issues such as the impacts of logging or forest conversion to other land uses, planners ideally require a comprehensive understanding of within drainage basin hydrological processes to determine the most vulnerable areas to increased storm runoff and erosion. Land managers in particular need to know the source areas and magnitude of inputs to the storm hydrograph, in terms of water quantity, sediment and solute transport; and the routing of such hydrographs from headwater to larger drainage basins. The latter includes an overall assessment at various scales of the impacts of forest disturbance and conversion on the water balance. This paper will focus on runoff generation in terms of identifying the various pathways and source areas. Such aspects will be linked with the need for a more comprehensive effort towards the field testing of so-called ‘physically based’ models of runoff generation. Some of the controversial issues arising from the difficulties in reconciling results from hydrochemical investigations with complementary hydrometric studies will be highlighted. Subsequently, attention will be given to topographic-wetness models, which have promising applications in forestland management. In addition, alternative simple models for application at the catchment scale will be assessed. The latter is in recognition that at smaller scales, heterogeneity both in time and space of soil hydraulic properties demand a greater number of parameters in modelling. Such considerations can even prove an obstacle in terms of the confident application of ‘physically based’ models. 相似文献
952.
953.
从分析小型污水处理厂实验室现状入手,指出当前污水处理厂实验室存在的问题,并就其规范化管理的重要性进行了探讨。 相似文献
954.
955.
森林景观格局研究中的尺度效应 总被引:2,自引:0,他引:2
以TM影像和野外调查为数据源,以3S技术为研究手段,从研究区域不同的取样尺度入手,分析了尺度变化对区域景观格局研究的影响.结果表明,研究区景观斑块的数量、最大斑块面积与取样面积之间关系密切.取样面积对景观格局的影响分析显示,在取样面积为研究区面积的70%时,景观多样性最高,平均多样性指数为1.854.当取样面积小于总面积的69%时,景观优势度指数呈增加的趋势.图4表2参16 相似文献
956.
Local-scale and large-scale factors can affect the presence of a species of understory vegetation in the forest. Local-scale
factors may be the influence of surrounding trees, while climate and latitude are typically considered large-scale factors.
A model for the presence of a species needs to take into account both scales. A conditional logistic model is proposed for
those studies where only the local-scale factors are of interest and that avoids estimating the large-scale parameters. Conditioning
is carried out by the number of quadrats in the plot where the vegetation is found. As the latter is a sufficient statistic
for the large-scale factors, a model free from these parameters is obtained. Data gathered in the permanent sample plots of
the 1985–1986 National Forest Inventory of Finland is used for illustration, where the local-scale factor of interest is the
influence of the trees, quantified by an index based on the size and location of the trees. The model fitted to Vaccinium vitis-idaea showed a significant and positive influence of Scots pine on the presence of this species, while for Calamagrostis arundinacea, a decrease in the odds ratio was observed due to the influence of Norway spruce. 相似文献
957.
论大学生思想政治工作进网络之紧迫性 总被引:1,自引:1,他引:1
李仕武 《湖南环境生物职业技术学院学报》2004,10(4):380-383
在对大学生利用网络的情况进行调查的基础上,总结出学生使用网络的现实基本状况,并分析学生上网存在的问题,指出学院的思想政治工作进网络的紧迫性。 相似文献
958.
Modeling joint production of wildlife and timber 总被引:2,自引:0,他引:2
Darek J. Nalle Claire A. Montgomery Jeffrey L. Arthur Stephen Polasky Nathan H. Schumaker 《Journal of Environmental Economics and Management》2004,48(3):997
Production of marketed commodities and protection of natural systems often conflict. A focus on only one goal can result in large losses in other goals and may result in inefficient and unsustainable outcomes. In this paper, we develop a method that combines economic and ecological models in a dynamic and spatial analysis to evaluate land use decisions and find cost-effective alternatives for which it is not possible to do better on one objective without harming another objective. The method is demonstrated using timber production and species conservation on a forested landscape over a 100-year planning horizon. Current land use strategies are simulated and compared with cost-effective alternatives. The approach is compared to a static reserve approach, similar to previous studies, and found to produce substantially more efficient management strategies for the case study landscape. 相似文献
959.
960.
The Spitzkoppe Community Campsite in western Namibia lies in an area with very limited water resources. Water scarcity places
a constraint on community income generation and development opportunities. The existing water resources are overexploited
and to ensure future water security, the community must take sustainable water management into consideration in their daily
lives and business ventures, including tourism. This has been successfully achieved at the Spitzkoppe Community Campsite through
a combination of high community motivation, organisation and action, the involvement of researchers and trainers in water
resource management and support from developers. The most appropriate water management solutions were found through ongoing
practical testing of different strategies and technologies over two years. This paper presents a case study of a community-based
tourist camp at Spitzkoppe and traces the community’s progress towards developing an alternative way to combat desertification
and a potentially lucrative tourist business. 相似文献