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1.
Regional Representativeness of Swedish Reference Lakes 总被引:1,自引:1,他引:0
Richard K. Johnson 《Environmental management》1999,23(1):115-124
/ Recent focus has been placed on ecoregion delineations for providing an appropriate framework for monitoring and assessment of region-specific attainable water/habitat quality. Using an ecoregion approach to stratify variance, this study was conducted to determine whether earlier (subjectively) selected Swedish reference lakes may be considered as regionally representative reference sites when compared with a randomly selected lake population. Predictive modeling by discriminant function analysis with lakes classified by ecoregion and lake surface area and six physicochemical variables showed that the greater majority of reference lakes may be considered as regionally representative. The highest proportion of lake "misclassifications" occurred in the boreonemoral ecoregion, a relatively diverse ecoregion of southern Sweden. This apparent bias may be in part be due to the criteria used in selecting regional reference lakes. In the earlier selection of reference lakes emphasis was placed on lakes not being adversely affected by land usage or pollutant discharges, consequently forest lakes were often overrepresented and sites in agricultural areas underrepresented in the selected reference sites. As a complement to predictive modeling, PCA ordination showed the placement of reference lakes within the random lake population and indicated where reference sites might be missing along potentially important ecological gradients. KEY WORDS: Regionalization; Ecoregion; Representativeness; Reference; Ordination; Modeling; Temperate lakes 相似文献
2.
针对传统PM2.5浓度空间分布模拟方法忽略了城市内部如道路、工厂、居民区、景区等不同微环境整体对PM2.5浓度影响机制的缺陷,本研究提出一种微环境PM2.5浓度场景分异的理论假设,并以湖南长沙主城区为例,结合基于污染先验知识划分的城市微环境场景空间分布与自主设计加密观测场获取的203个监测点小时PM2.5浓度加密数据,分析城市微环境PM2.5浓度场景时空分异特征.在此基础上,耦合地理加权回归(GWR)与人工神经网络(ANN)方法,构建微环境场景增强下的PM2.5浓度空间分布精细模拟GWR-ANN模型,开展城市内部高空间分辨率PM2.5污染制图.结果表明:不同微环境场景间PM2.5浓度存在显著时空差异,地表覆盖类型相同但分别位于2个不同场景的监测点间PM2.5浓度差会随时间发生变化;耦合微环境场景变量的GWR-ANN模型能够有效精细模拟PM2.5浓度的空间分布,模型拟合效果与交叉检验精度指标整体优于无场景变量参与的GWR-ANN模型(除部分时相较为接近外,检验R2:0.76~0.84vs.0.57~0.81);场景增强下的PM2.5浓度空间分布100m级分辨率模拟估算结果可以较好揭示研究区PM2.5浓度高低值局地变化特征. 相似文献
3.
广东省环境库兹涅茨特征分析 总被引:25,自引:0,他引:25
介绍了环境库兹涅茨假说经验结论,对其所涉及的环境质量随着经济增长出现"先恶化,后改善"的现象进行了分析,指出环境质量的变化不会自动产生,必须在环境政策的干预下才能实现.结合广东省废水、废气以及CODCr和SO2等污染物排放量及经济增长数据,构建了广东省环境库兹涅茨曲线,实证分析了广东省经济增长与环境质量之间的关系;经过"十五"以来的环境综合整治,广东省废水和废气排放总量正在并将逐渐继续下降,部分环境指标正在接近转折点. 相似文献
4.
Rothley KD 《Environmental management》2006,38(3):327-337
Many reserve selection tools have been created to solve the minimum representation problem, selecting the least costly set
of sites such that all conservation surrogate targets are met. However, there are practical problems and risks associated
with this method for finding reserve network alternatives, including the treatment of persistence-promoting design considerations
as secondary objectives. Here, reserve networks are generated for a hypothetical landscape where the objectives are to maximize
representation and to maximize conformance with persistence-promoting design principles, subject to a constraint on the number
of sites in the networks. The efficiency of potential networks is calculated as the total number of species captured in the
included sites. Effectiveness is measured as a function of the size of individual patches, total reserve size, and extent
of interpatch connectivity. A series of tradeoff curves are produced showing the nondominated compromise alternatives between
representation and design for organisms with varying dispersal capabilities. Each alternative comprises a list of selected
sites and covers species, as well as the identities and locations of the interpatch edges connecting the sites. Potential
ways to use the results are discussed. 相似文献
5.
The Influence of the Pacific Decadal Oscillation on Annual Floods in the Rivers of Western Canada
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Sunil Gurrapu Jeannine‐Marie St‐Jacques David J. Sauchyn Kyle R. Hodder 《Journal of the American Water Resources Association》2016,52(5):1031-1045
We analyzed annual peak flow series from 127 naturally flowing or naturalized streamflow gauges across western Canada to examine the impact of the Pacific Decadal Oscillation (PDO) on annual flood risk, which has been previously unexamined in detail. Using Spearman's rank correlation ρ and permutation tests on quantile‐quantile plots, we show that higher magnitude floods are more likely during the negative phase of the PDO than during the positive phase (shown at 38% of the stations by Spearman's rank correlations and at 51% of the stations according to the permutation tests). Flood frequency analysis (FFA) stratified according to PDO phase suggests that higher magnitude floods may also occur more frequently during the negative PDO phase than during the positive phase. Our results hold throughout much of this region, with the upper Fraser River Basin, the Columbia River Basin, and the North Saskatchewan River Basin particularly subject to this effect. Our results add to other researchers' work questioning the wholesale validity of the key assumption in FFA that the annual peak flow series at a site is independently and identically distributed. Hence, knowledge of large‐scale climate state should be considered prior to the design and construction of infrastructure. 相似文献
6.
In nature reserves and habitat conservation areas, monitoring is required to determine if reserves are meeting their goals for preserving species, ecological communities, and ecosystems. Increasingly, reserves are established to protect multiple species and communities, each with their own conservation goals and objectives. As resources are always inadequate to monitor all components, criteria must be applied to prioritize both species and communities for monitoring and management. While methods for prioritizing species based on endangerment or risk have been established, approaches to prioritizing ecological communities for monitoring are not well developed, despite a long-standing emphasis on communities as target elements in reserve design. We established guidelines based on four criteria derived from basic principles of conservation and landscape ecology--extent, representativeness, fragmentation, and endangerment--to prioritize communities in the San Diego Multiple Species Conservation Plan (MSCP). The MSCP was one of the first multiple-species habitat conservation areas established in California, USA, and it has a complex spatial configuration because of the patterns of surrounding land use, which are largely urbanized. In this case study, high priority communities for monitoring include coastal sage scrub (high endangerment, underrepresented within the reserve relative to the region, and moderately fragmented), freshwater wetlands, and coastal habitats (both have high fragmentation, moderate endangerment and representativeness, and low areal extent). This framework may be useful to other conservation planners and land managers for prioritizing the most significant and at-risk communities for monitoring. 相似文献
7.
Introduction:The quasi-induced exposure (QIE) method has been widely implemented into traffic safety research. One of the key assumptions of QIE method is that not-at-fault drivers represent the driving population at the time of a crash. Recent studies have validated the QIE representative assumption using not-at-fault drivers from three-or-more vehicle crashes (excluding the first not-at-fault drivers; D3_other) as the reference group in single state crash databases. However, it is unclear if the QIE representativeness assumption is valid on a national scale and is a representative sample of driving population in the United States. The aims of this study were to assess the QIE representativeness assumption on a national scale and to evaluate if D3_other could serve as a representative sample of the U.S. driving population. Method: Using the Fatality Analysis Reporting System (FARS) and the National Occupant Protection Use Survey (NOPUS), distributions of driver gender, age, vehicle type, time, and roadway type among the not-at-fault drivers in clean two-vehicle crashes, the first not-at-fault drivers in three-or-more-vehicle crashes, and the remaining not-at-fault drivers in three-or-more vehicle crashes were compared to the driver population observed in NOPUS. Results: The results showed that with respect to driver gender, vehicle type, time, and roadway type, drivers among D3_other did not show statistical significant difference from NOPUS observations. The age distribution of D3_other driver was not practically different to NOPUS observations. Conclusions: Overall, we conclude that D3_other drivers in FARS represents the driving population at the time of the crash. Practical applications: Our study provides a solid foundation for future studies to utilize D3_other as the reference group to validate the QIE representativeness assumption and has potential to increase the generalizability of future FARS studies. 相似文献
8.
Brendan G. Mackey Henry A. Nix Michael F. Hutchinson June P. Macmahon P. Michael Fleming 《Environmental management》1988,12(4):501-514
Problems arising from application of the representative criterion for conservation and natural heritage evaluation are discussed. An ecological basis to this criterion is suggested that focuses on those key environmental factors dominating biotic response. A methodology is proposed that utilizes computer-based methods of establishing and interrogating spatial data bases (geographic information systems), environmental modeling, and numeric analysis. An example is presented illustrating some of the advantages and limitations of classification and dimension reduction techniques in both defining bioenvironments and displaying their spatial distribution. The advantages of this method for representativeness evaluation are that it maximizes the utility of available data, is explicit and repeatable, and enables large areas to be analyzed at relatively fine scales. 相似文献
9.
1951-2010年珠江流域洪水极值序列平稳性特征研究 总被引:1,自引:0,他引:1
水文序列的平稳性假设是传统水文统计学方法在水文序列分析研究中的基本假设,随着气候变化与人类活动对地表水文过程的影响,这种假设往往存在问题,使水文分析得出误导性结论。以珠江流域28个测站1951—2010年年最大洪峰流量序列为例,用Pettitt方法结合Loess参考函数检验序列中均值和方差变异,用Mann-Kendall(MK)和Spearman法检测时间趋势性,用广义可加模型(GAMLSS)和长期持续效应等具体分析序列的平稳性。研究结果表明:1均值/方差变异主要集中在西江和东江流域,变异时间分别集中在1990年左右和1968—1987年间;2变异点的存在与否对序列趋势检验结果有重要影响,在考虑变异点前提下,珠江流域年最大洪峰流量序列基本无显著趋势性;3在GAMLSS模型中,对于不具有和具有突变点序列,Gamma分布均为选择次数最多的最优极值分布,不具有突变点序列分布参数θ1或θ2非平稳模型与平稳模型差距较小,具有突变点序列则相反;4统计上检测出具有突变点或者显著时间趋势性的测站,同样检测出高Hurst系数,反之亦然。Hurst系数估计因样本容量较小具有较大不确定性。东江流域受流域内水利工程的剧烈影响,尽管检测出高Hurst系数,但仍认定为非平稳序列;西江干流主要受支流汇流和气候变化影响,高Hurst系数表明其水文过程可能是长期稳定过程中局部波动的结果。 相似文献
10.
A comparison of simulated and observed ozone mixing ratios for the summer of 1998 in Western Europe 总被引:1,自引:0,他引:1
H. Schmidt C. Derognat R. Vautard M. Beekmann 《Atmospheric environment (Oxford, England : 1994)》2001,35(36):6277-6297
This study describes and evaluates the newly developed European scale Eulerian chemistry transport model CHIMERE-continental. The model is designed for seasonal simulations and real time forecasts without the use of super-computers. For the purpose of model evaluation simulated ozone mixing ratios for the period between 1 May 1998 and 30 September 1998 are compared to observational data from 115 European surface sites. In order to facilitate the interpretation of future forecasts a statistic is established to estimate the reliability of a simulated pollution level. Besides this, the comparison is done by means of time series, scatter plots, a spectral analysis and the calculation of RMS-errors and biases of the model results corresponding to each observation site. It turns out that the mean RMS-error of the simulated daily maximum ozone mixing ratio for the sites considered a priori as well suited for a model comparison is about 10 ppb. For the same period but a reduced number of sites observed concentrations of NO2 and ethene are compared to simulated values. Difficulties encountered with the representativeness of observations when trying to evaluate a mesoscale air pollution model are discussed. 相似文献