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191.
从气候、淡水资源和海洋资源等方面简要介绍了山东省的水产资源自然条件,概述了主要淡水虾和海水虾的资源及其分布。从养殖规模和养殖模式两方面总结了主要经济虾类的养殖现状,指出了优质虾苗繁殖困难、病害防治水平低、产品质量差、销售渠道狭窄等制约虾类养殖业发展的主要问题,并据此提出了相应的对策。 相似文献
192.
David M. Greer 《Environmental management》1982,6(3):217-229
An urban population of ducks in Puyallup, Washington, USA was studied for 14 consecutive months beginning in November 1978. Observations were made weekly from four study sites where ducks would congregate at early morning hours. Factors contributing to the presence of waterfowl in Puyallyup included abundant food supplies and a creek corridor that connected fragmented habitats in the urban area to the larger rural populations of waterfowl. Mallards (Anas platyrhynchos) were the most abundant of the 13 species observed and were the only ducks remaining during the nesting season. Habitat size and complexity were important factors influencing the species diversity of a particular site. Nesting success of mallards was poor due to limited distribution of nesting habitat, intraspecific aggression, and human disturbance. Both site-specific and more broad-based strategies are suggested for managing and planning for duck populations in urban areas. 相似文献
193.
Early research showed that citizens’ environmental concern in the United States was linked to three individual-level factors: socio-demographic variables, political orientations, and personal beliefs or worldviews about human-nature relations. Given many changes in the American society over the last several decades, one important, yet unanswered question is whether these factors still drive public environmental concern in the United States today, and if so, to what extent. This study, drawing from extant theoretical and empirical studies, aims to reinvestigate the determinants of citizens’ environmental concern by employing three national public surveys conducted in 2004, 2007, and 2013. Our data analyses confirm and expand the findings of previous research on the significance and importance of political ideology, fundamental beliefs about human-nature relations, and certain socioeconomic factors such as gender and race in explaining citizens’ environmental concern. More specifically, political liberals, people with higher New Ecological Paradigm values, females, and Non-Whites tend to be more concerned about environmental problems than their counterparts are. Our data analyses also reveal some interesting findings when compared to many previous studies: first, our data indicate a positive relationship between age and environmental concern, suggesting that older people in the United States are more concerned about the environment than younger adults; second, unlike most past research showing a positive Education-Environmental Concern relationship, our study suggests that education level seems to have little effect in explaining citizens’ environmental concern measured in this study. Key implications for environmental policymaking and recommendations for future research are discussed in the conclusion. 相似文献
194.
定位研究了25a来缙云山银木荷林物种组成及多样性在自然演替过程中的动态变化。结果表明,银木荷林维管植物物种由57种(隶属于24科,46属)减少到38种(隶属于19科,26属)。林下草本和层间植物逐渐消失,胸径大于7.5cm的乔木层树总胸断面积有所减少。尽管群落物种组成以及多样性发生改变,但是银木荷依然是优势树种,处于林冠层,而林冠亚层的白毛新木姜子、四川山矾、长蕊杜鹃逐渐增多,短刺米槠逐渐减少。群落乔木层4个α多样性指数都呈下降趋势,丰富度指数由2.98下降为1.99,Shannon-Wiener指数25a间减小了0.34,Simpson指数和Pielou指数变化都很小;β多样性分析结果显示,银木荷群落的物种差异很大。研究表明,25a间群落物种差异显著。揭示缙云山银木荷林自然演替过程中的物种组成和多样性变化规律,可为缙云山保护区及长江流域中上游亚热带常绿阔叶林的银木荷群落的管理提供一定的参考价值。 相似文献
195.
Jukka Lehto Jussi Paatero Reijo Pehrman Seija Kulmala Juhani Suksi Teija Koivula Timo Jaakkola 《Journal of environmental radioactivity》2008,99(10):1656
Lichen–soil column samples were taken from several locations in the Southern Finland between 1986 and 2006. Columns were divided into three parts, upper lichen, lower lichen and underlying soil, and their gamma emitting radionuclides, 134Cs, 137Cs, 103Ru, 95Zr, 106Ru, 110mAg, 125Sb and 144Ce, were measured with gamma spectrometry. Deposition values were calculated as Bq/m2 for each sampling site. Distribution of various radionuclides in the three compartments as a function of time was determined. Both effective and ecological half-lives of all radionuclides were calculated for upper lichen, whole lichen and whole lichen–soil column. A linear relation was derived between the physical half-lives and effective half-lives for whole lichen and for whole lichen–soil column. Reindeer meat activity concentrations of various radionuclides and ensuing radiation doses to reindeer-herding people were also estimated for a hypothetical case where a similar high radioactive pollution, as was taken place in the Southern Finland, would have occurred in the reindeer-herding areas in the Finnish Lapland. 相似文献
196.
Qinhua Fang Luoping Zhang Huasheng Hong Liyu Zhang Frances Bristow 《Environment, Development and Sustainability》2008,10(1):41-49
Environmental planning at different levels has been called for by environmental departments in China during last years to
integrate environment consideration to economic development. Based on the accomplished environmental planning practice in
Xiamen China, the paper suggests a general environmental planning process with ecological function zoning as its key steps,
at the same time an effective method for ecological function zoning was formulated. The case studies of Dongfu suburban town
environmental planning and Xiamen eco-city conceptual planning indicate that scientifically sound results of ecological function
zoning can contribute to improving not only the adaptability and acceptability of environmental planning, also the environmental
management and the decision-making. The experience shows that the ecological function zoning methods should be applied according
to the principles of adaptive management, resource-based and community-based, so that it can integrate science into decision-making
process, avoiding both narrow-minded viewpoints of planners and natural resource use conflicts among variety of stakeholders.
Problems to be resolved in the future are also pointed out in the ending part. 相似文献
197.
198.
Rethinking receiver operating characteristic analysis applications in ecological niche modeling 总被引:2,自引:0,他引:2
The area under the curve (AUC) of the receiver operating characteristic (ROC) has become a dominant tool in evaluating the accuracy of models predicting distributions of species. ROC has the advantage of being threshold-independent, and as such does not require decisions regarding thresholds of what constitutes a prediction of presence versus a prediction of absence. However, we show that, comparing two ROCs, using the AUC systematically undervalues models that do not provide predictions across the entire spectrum of proportional areas in the study area. Current ROC approaches in ecological niche modeling applications are also inappropriate because the two error components are weighted equally. We recommend a modification of ROC that remedies these problems, using partial-area ROC approaches to provide a firmer foundation for evaluation of predictions from ecological niche models. A worked example demonstrates that models that are evaluated favorably by traditional ROC AUCs are not necessarily the best when niche modeling considerations are incorporated into the design of the test. 相似文献
199.
A multiple criteria evaluation of sustainable agricultural development models using AHP 总被引:2,自引:0,他引:2
Selection of the appropriate agricultural development model has become an important issue in Iran. Using data from Fars province
of Iran, the purpose of this paper is to use analytic hierarchy process (AHP) for selecting between the two competing sustainable
agricultural development models, which have been developed based on the general tenets of Ecological Modernization (EM) and
De-Modernization (DM) theories. Farmers, environmentalists, board members of rural cooperative, rural women and experts from
Fars Agricultural (Jehad-e-Keshavarzi) Organization participated in application of AHP to this study. They applied AHP to
determine the priority of DM and EM based sustainable agricultural development models. Each group determined the priority
of the two models for sustainable agricultural development. The findings indicated that ecological criteria i.e. wise use
of resources, environmental protection and product quality are the most important criteria for sustainable agriculture of
Iran, followed by economic criterion employment and social criterion participation. A sensitivity analysis was carried out
to determine the critical factors that affected the priority of alternatives. The results indicated that EM-based sustainable
agricultural development model has a higher priority as the theoretical base of agricultural development of Iran.
Readers should send their comments on this paper to BhaskarNath@aol.com within 3 months of publication of this issue 相似文献
200.
In contrast to Europe, the USA and South Africa, Australia has no specific, overarching federal legislation to underpin a nationally-coordinated framework for monitoring, assessing and reporting estuarine condition. This has resulted in a complex mosaic of diverse approaches and governance structures, hindering the ability to make inter-State comparisons. In this second part of a comprehensive three-part review, we present a systematic appraisal of current and impending approaches for measuring and reporting estuarine condition in each of Australia’s States and Territories. A concise summary is provided in each case, supported by extensive appendices containing detailed accounts of relevant monitoring and reporting programs. We synthesise and evaluate this output at the State/Territory level, highlighting areas of improvement and major gaps. 相似文献