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361.
Indirect Effects of Biological Control on Plant Diversity Vary across Sites in Montana Grasslands 总被引:3,自引:0,他引:3
Abstract: Biological control with specialist, nonindigenous, herbivorous insects is an important option for controlling invasive exotic plants in wildlands and nature reserves. It is assumed that biological control agents will reduce the dominance of the target weed, thereby increasing the native diversity of the associated plant community. However, this hypothesis has rarely been tested. We introduced Aphthona nigriscutis into grassland sites infested with the invasive exotic species Euphorbia esula L. on a nature reserve in Montana (U.S.A.). Two sites with better soil had been treated previously with herbicide, whereas two other sites had not. We measured the density and biomass of Euphorbia vegetative and flowering stems and number of native and exotic shrubs, grass-like plants, and forbs in 48 microplots in Aphthona release and control macroplots at each site. After 5 years, Aphthona release was associated with a 33–39% decline in Euphorbia aboveground biomass compared with controls at all sites. Other effects of the biocontrol depended on the site. Biocontrol slowed the recovery of species diversity at the sites previously treated with herbicide but slowed the loss of diversity at sites without a history of herbicide. Biocontrol introduction was not associated with a disproportionate increase in nontarget exotic species. Release of Aphthona caused a decline in the biomass of flowering stems relative to controls at good-soil, previous-herbicide sites but was associated with a relative increase in flower stem mass at poor-soil, no-herbicide sites. Our results suggest that biocontrol reductions in weed dominance will not always be associated with increased species diversity. More emphasis should be placed on conserving desirable communities and less on simple weed control. Monitoring of community-level effects should accompany biocontrol introductions on nature reserves. 相似文献
362.
分析了松华坝水源保护区新能源利用现状及存在的问题,在此基础上,对保护区新能源结构进行了规划,并进行了经济技术分析。 相似文献
363.
364.
应急物资储备库是应急救援的重要载体,储备库选址是否科学合理决定着整个应急公共服务体系的成效,而传统遗传算法在研究储备库选址与物资调配相结合的问题上存在局限性。针对这一问题,从需求点及应急设施服务质量视角构建基于覆盖满意度和经济性的应急设施选址与物资调配优化模型,并根据模型设计自适应遗传算法(AGA),结合储备库实际情况采取具有方向性的初始群体生成法提高搜索速度,设计自适应交叉与变异算子使AGA能够在进化速度与解的质量之间进行权衡,并获得全局最优解。结果表明,该算法能跳出局部最优从而获得最优的选址-分配方案,可为应急管理部门和决策机构的应急设施选址规划及应急物资分配提供理论依据和决策参考。 相似文献
365.
Abstract Emergency resources are an important basis of effective emergency response. But there are many disadvantages of the Chinese traditional material reserve method in which the resources are separately reserved in different regions and sections according to the kinds of disasters. So there comes the Multi-formal and Information- based Emergency Resource Reserve System (MIERRS) in China. The reserve body and method change from the single into the multiple forms, that is, the main reserve body changes from the single government agency into the organizations combining with the military, enterprise and society, and the reserve method changes from single material reserve into the reserve combining with market reserve, talents and technology reserve, and production capacity reserve. The content of the reserve change from material to information means to develop the Emergency Resource Management Information System realizing real-time control of resource characteristics and relevant reserve information. The MIERRS leads to a reserve system with rapid response and flexible schedule. It provides a convenient platform for resource sharing, thus avoiding duplication and waste, improving the utilization of resources, reducing the reserve loss and optimizing the structure of resource reserve. 相似文献
366.
利用RAPD(随机扩增多态)标记分析湖内鲤、鲫群体遗传多样性,从40个随机引物中各筛选出8个引物适合鲤、鲫群体RAPD扩增。在鲤群体中,共检测出60条带,其中多态性带42条,多态位点比率为70.00%;而在鲫群体中,共检测出61条带,其中多态性带40条,多态位点比率为65.57%。用POPGENE软件分析实验数据,结果显示:湖内鲤群体的遗传多样性水平(He=0.230 1,H0=0.391 0)和鲫群体的遗传多样性水平(He=0.218 6,H0=0.375 8)都较高,都有较大的遗传变异。而在鲤、鲫群体内,雌性群体与雄性群体相比较,其各自的遗传多样性很接近。 相似文献
367.
Biosphere reserves, designated under UNESCO’s Man and the Biosphere (MAB) Programme, are now regarded as key mechanisms to achieve global imperatives such as the Sustainable Development Goals. The concept of biosphere reserves has evolved significantly from the 1970s to include a larger number of functions and zones, as well as the inclusion of stakeholders in governance, as codified in the 1996 Statutory Framework for the World Network of Biosphere Reserves. Its implementation has led to the re-territorialisation of 66 biosphere reserves, as they have been extended beyond the protected areas that form their ‘core areas’. One example is Wester Ross in northwest Scotland. This region has been nationally recognised for its high biodiversity and landscape values since the late 1940s, and a small biosphere reserve was established in 1976. In the current decade, as required by the MAB Programme, this biosphere reserve was extended to over 100 times its original area through a participatory process which is described in detail. Following re-territorialisation, this biosphere reserve, like others, both represents opportunities and faces challenges. These are discussed with regard to four requirements: effective communication, stakeholder engagement, participatory governance, and funding. 相似文献
368.
本文论述了自然保护区评价这一新学科在近30年内的发展史,同时介绍了自然保护区评价的几个组成部分和一些基本概念,分析了其存在的不足和有待解决的问题。 相似文献
369.
Lars T. Waser Meinrad Kuechler Markus Schwarz Eva Ivits Silvia Stofer Christoph Scheidegger 《Environmental Modeling and Assessment》2007,12(4):315-328
The present study focuses on developing models to predict lichen species richness in a UNESCO Biosphere Reserve of the Swiss
Pre-Alps following a gradient of land-use intensity combining remote sensing data and regression models. The predictive power
of the models and the obtained r ranging from 0.5 for lichens on soil to 0.8 for lichens on trees can be regarded as satisfactory to good, respectively. The
study revealed that a combination of airborne and spaceborne remote sensing data produced a variety of ecological meaningful
variables. 相似文献
370.
Mathematical Methods for Spatially Cohesive Reserve Design 总被引:1,自引:0,他引:1
Mark D. McDonnell Hugh P. Possingham Ian R. Ball Elizabeth A. Cousins 《Environmental Modeling and Assessment》2002,7(2):107-114
The problem of designing spatially cohesive nature reserve systems that meet biodiversity objectives is formulated as a nonlinear integer programming problem. The multiobjective function minimises a combination of boundary length, area and failed representation of the biological attributes we are trying to conserve. The task is to reserve a subset of sites that best meet this objective. We use data on the distribution of habitats in the Northern Territory, Australia, to show how simulated annealing and a greedy heuristic algorithm can be used to generate good solutions to such large reserve design problems, and to compare the effectiveness of these methods. 相似文献