Effects of Married-Couple Dual-Earner Households on Metropolitan Commuting: Evidence from the Atlanta Metropolitan Area

The idea of creating a balance between jobs and housing within different commuter catchment areas of a metropolis has been a prominent approach for reducing traffic congestion, air pollution, and journey-to-work times. Married-couple, dual-earner households, in which both spouses are employed, have been identified as an obstacle to the job-housing balance concept because of their constrained ability to choose a residential location near both workplaces. However, this has not yet been conclusively tested. Drawing on the 2000 5% PUMS dataset for metropolitan Atlanta, this article examines the commuting behavior of such households relative to single-earner households. The results challenge the dominant assumption that the average commutes of married-couple, dual-earner households are necessarily longer than those of single-earner households. In fact, after controlling for all forms of socioeconomic factors in the analysis, this study shows there are either no significant differences, or if there are, the average commutes of single-earner households are longer. It is a lack of affordable housing near job locations, or vice versa, and not the presence of dual-earner households, that should be blamed for lengthening commuting time and difficulties in implementing job-housing balances.     

Residential Settlement Patterns among Immigrants in Atlanta Metropolitan Area,Georgia

This study investigates the diversity of immigrant populations and their spatial residential patterns at the census tract level within twenty‐nine counties of the Atlanta Metropolitan Statistical Area (MSA), using 2013 American Community Survey (ACS) five‐year estimates summary data from 2008–2012. Correlations coefficient analyses with local job opportunities, education level, and English proficiency and the presence of foreign‐born populations are also discussed. We find that immigrants have different patterns of settlement depending on their place of birth and region of origin. Local job opportunities, dominant language at home, and education levels also relate to the distribution of foreign‐born populations. Further research opportunities concerning differential settlement are discussed.     

Linking Home to Work: Ethnic Labor Market Concentration in the San Francisco Consolidated Metropolitan Area

Different perspectives have been offered to explain ethnic labor market concentrations. In most studies, however, residential places are seldom included in the research framework. Using data from 5% Public Used Microdata Samples in 2000, this case study of the San Francisco Bay Area reveals that the robust growth of the new economy is dramatically segmenting the geography of employment and thereby the spatial division of labor in each ethnic group. Living arrangements, such as central-city residence and living in coethnic-concentrated-PUMAs, increase the chances of niche employment for most racial/ethnic groups, even after controlling for human capital and certain local context factors. However, there is a "substitution" effect between personal socioeconomic status and location factors. This study argues that living arrangements can provide a mechanism through which personal characteristics, social networking, and ethnic recourses interact with macroeconomic trends, and thus carve out local labor market experiences across the urban space.     

The Suburbanization of Food Insecurity: An Analysis of Projected Trends in the Atlanta Metropolitan Area

Although general patterns of food insecurity in the United States are known, few studies have attempted to estimate small area food security or account for ongoing socioeconomic changes. Here we address these issues by producing small area estimates of food insecurity in the Atlanta metropolitan area using two methodologies: fixed effects modeling and demographic metabolism. In both cases, we use county-level data from the Current Population Survey to determine the association between food insecurity and demographic predictors. These associations are then applied to tract-level data from the 2009 to 2013 American Community Survey and projected data for 2020 to create small area estimates of food insecurity. We find broad consensus between our two methods. For both time periods, food insecurity is highest in southern sections of the city of Atlanta and its neighboring suburbs. Projections to 2020, however, show that food insecurity rates are projected to increase in outer-ring suburbs east and west of the city while decreasing in the urban core. These results highlight the need to further adapt antihunger efforts for often sprawling suburban communities, where poverty rates are increasing but spatial mismatch combined with poor transit access might hinder access to food assistance.     

Human-Environment Patterns of Metropolitan Spatial Restructuring:Atlanta,Georgia and Shanghai,PRC,1950-2000

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Whither the Jobs: Identifying Concentrations of Employment in Metropolitan Areas

Large concentrations of employment have developed outside traditional central business districts. Our research focuses on analyzing the changing distribution of employment in metropolitan areas by using tract-to-tract commuting data from Census 2000 to identify high-employment nodes within large metropolitan areas. We propose a new way to delineate clusters of contiguous high-employment tracts based on the job density in these areas. We then compare outlying employment clusters with traditional central business districts and contrast employment clusters of varying job densities. Our method has several advantages over existing methods of identifying employment clusters: it is conceptually simple, can use publicly available data, relies on a standardized geographic unit applicable across the entire United States, and offers the ability to examine data from multiple census years.     

Racial Variations in Males' Commuting Times in Atlanta: What Does the Evidence Suggest?*

Using a sample from the comparatively most privileged group of black males, those married and living with a working spouse, this article investigates how race‐based residential locations and the spatial structure of labor markets affect commuting experiences. This research uses the most sophisticated commuting data available at the time the research was conducted, the 1990 5 percent Public‐Use Microdata Samples for the Atlanta Metropolitan Area, and again confirms severe spatial mismatch problems for central‐city blacks, regardless of socioeconomic status, household formation, and access to automobiles. However, the situation with black males living in suburban areas differs significantly as those in the southern (predominantly black) suburbs show considerable evidence of spatial mismatch, whereas the northern (predominantly white) suburbs show no such evidence.     

北京都市区人口—就业分布与空间结构演化

本研究应用非参数计量方法,实证刻画北京都市区人口—就业空间分布演化,揭示在快速城市化和城市增长背景下,北京都市区空间结构特征及发展趋势。研究发现,北京都市区人口和就业分布都呈现多中心空间结构。20 世纪80 年代以来,随着人口郊区化,北京都市区人口次中心数量不断增加,并由近郊向远郊扩展,人口分布呈现明显的分散化和多中心化趋势,但人口分散的空间范围还比较有限。与人口的分散化趋势不同,2004-2008 年,北京都市区就业仍呈现向心集聚的趋势,造成远郊就业次中心的影响不断被弱化,都市区空间结构的多中心性有所降低。这说明北京都市区的单中心或强中心结构可能并未从根本上改变,且人口的分散化和就业的向心集聚导致宏观面上人口—就业的空间失衡。北京都市区多中心空间结构的形成,需要强化郊区次中心的集聚能力,同时注重人口—就业的平衡布局,这是未来北京都市区空间结构调整的重点。     

The Role of Residential Location in Conditioning the Effect of Metropolitan Economic Structure on Male Youth Employment

Youths have increasingly experienced labor market problems over the last several decades. One fruitful line of explanation focuses on structural changes in the demand for labor stemming from deindustrialization, changing skill requirements for employees, and increasing supply competition from women and recent immigrants. While these explanations merit attention, they have not adequately considered facts that condition their impact. This paper considers the argument that intra-metropolitan residential location conditions the effects of metropolitan labor market structure on black and white male youths' employment probabilities. Using a sample of individual-level data drawn from the 1990 census combined with metropolitan-level indicators of economic structure, it was found that some structural effects varied between central-city and suburban male youths. The conditioning role of residential location, and the subsequent nature of the structural effects, varied considerably between black and white male youths. Interpretations of the conditioning role of residential location include a variety of social and institutional effects on individual residents and the stigmatizing effects of some neighborhoods, especially on black male youths.     

生态位理论在我国城市发展中的应用

该文将生态位理论用于城市研究，引入城市人口生态位和城市生态场势，并用二者的均衡协调程度分析了我国18个中心城市的发展现状，具体分为协调型，低人口生态位，高城市生态场势型和高人口生态位，低城市生态场势型三种类型，并针对不同的类型提出了今后的发展方向和发展重点。     

生态位理论与方法在城市研究中的应用

引入生态学重要基础理论生态位理论,认为其在城市研究中有重要作用。表现在:生态位态势变化及生态位大小能够反映城市一般发展规律和城市特征,生态位适宜度可为城市经济发展方式的选择提供依据,生态势理论有助于城市发展动力机制的解释,生态位扩充则是城市空间结构发展和演化的生态学解释,而生态位重叠和分离理论对城市产业布局及其调整有很好的指导作用。     

祁连山北坡青海云杉林生境特征分析

青海云杉林分布格局深受环境影响,量化其分布与环境之间的关系对该种群管理、恢复与重建具有重要的意义,但目前仍然缺乏量化研究成果。本研究选择祁连山北坡青海云杉林为研究对象,以数字高程模型(digital elevation model,DEM)和青海云杉林分布图为基础数据,利用地理信息系统(GIS)空间分析方法,着重量化分析祁连山青海云杉林的生态幅度和地形特征,得出祁连山北坡青海云杉生境的气候边界函数,并界定青海云杉林分布的海拔、坡度以及坡向范围。该项研究目的在于数量化表达青海云杉林空间分布的气候和地形幅度,为退耕退牧还林提供科学支撑,为气候变化条件下青海云杉林的响应研究奠定基础。     

美国的"都市区域主义"及其引发的思考

1990年以来在西方国家掀起了"都市区域主义"复兴的热潮,美国的实践具有代表性。文章批判地总结了美国历史上"都市区域主义"的发展,从多个角度对当前大都市区域合作的复兴和区域管治进行分析,并对其引发的思考和对中国的启示进行了探讨。     

额济纳绿洲植物群落种间关系和生态位研究

根据61个天然植物群落样地的野外调查资料,采用生态位测度、方差比率法和基于2×2列联表的χ2检验、Ochiai关联指数、Pearson积矩相关系数和Spearman秩相关系数等方法,对额济纳绿洲植物群落主要物种进行了生态位和种间关联分析。结果表明：（1）胡杨（Populus euphratica）、柽柳（Tamarix ramosissima）、苦豆子（Sophora alopecuroide）生态位宽度值大,分别为该区的泛化种和乔木层、灌木层及草本层的优势种;（2）额济纳绿洲植物群落物种的总体联结性为不显著的正联结,大多数种对间呈中性联结（χ2<3.841,p>0.05）,物种趋向于独立分布。（3）种间联结系数（Ochiai指数）与生态位重叠之间极显著正相关,而生态位宽度与生态位重叠之间并无直接线性关系。     

开封市的城市生态位变化分析

城市生态位作为生态学重要理论之一,用于分析城市生态不同功能模块间竞争、演化等现象。通过以开封市不同功能模块为研究对象,在各模块污染指数和适宜度指数的基础上,运用生态位理论和方法,探讨改革开放以来,特别是近十年来开封市不同功能模块生态位格局变化规律,并对变化的原因进行了分析。研究结果表明：(1) 1994~2003年开封市自然生态环境系统各模块生态位呈上升趋势的有大气环境模块、城市绿化模块,而呈下降趋势的有水环境模块、声环境模块。(2) 1994~2003年开封市经济系统各模块生态位呈上升趋势的是第三产业模块,呈下降趋势的是第二产业模块,而变化不大的是第一产业模块。(3) 1994~2003年开封市社会系统各模块适宜度生态位呈上升趋势的有社会基础设施模块、社会资源配置模块、社会生产与保障模块,而呈下降趋势的只有人口模块。(4) 国家政策体制的改革是改革开放以来特别是近十年来开封市各功能模块生态位发生变化的最直接和最根本的原因。该研究不但对城市不同功能模块的宏观规划、经济发展和环境保护有具体的指导意义,而且对拓展城市生态学理论、研究复合生态系统的内在作用机制也同样具有重大的理论和现实意义。     

辽东山地老秃顶子古冰缘地貌植物种群生态位特征

基于48块样地的群落调查数据,以样地代表多种资源的综合状态,以物种重要值作为生态位计测的状态指标,采用Levins指数与Schoener指数,对辽东山地老秃顶子古冰缘地貌植物群落乔木层、灌木层及草本层植物的生态位特征进行了系统研究。结果表明：① 乔木层内臭冷杉（Abies nephrolepis）生态位宽度最大,为泛化乔木种;臭冷杉与长白鱼鳞云杉（Picea jezoensis var. komarovii）的生态位重叠值高达0.616,共优生存于暗针叶林中。② 灌木层内生态位宽度较大的狗枣猕猴桃（Actinidia kolomikta）、单花忍冬（Lonicera subhispida）、大翅卫矛（Euonymus macropterus）和关东丁香（Syringa velutina）为落叶阔叶林和针阔混交林下的泛化种;狗枣猕猴桃与单花忍冬的生态位重叠值高达0.610。③ 草本层内生态位宽度较大的东北羊角芹（Aegopodium alpestre）、荨麻叶龙头草（Meehania urticifolia）、酢浆草（Oxalis corniculata）为研究区泛化草本植物;东北羊角芹与荨麻叶龙头草的生态位重叠值高达0.702。     

Job/Housing Imbalance and Commuting Time in the Atlanta Metropolitan Area: Exploration of Causes of Longer Commuting Time

Commuting is the major source of congestion and air pollution in the United States. For almost a decade, urban policy-makers have been concerned about the geographical balance between locations of jobs and housing as a strategy for reducing traffic congestion and air pollution in American cities. Despite the popularity and apparent acceptance of the job/housing (J/H) imbalance concept among public policy-makers, little empirical research has been done on the J/H imbalance and how it relates to commuting patterns. This research examines commuting patterns in the Atlanta metropolitan area to determine the extent to which commuting flow volume is the result of an imbalance between the location of home and workplace by using the most sophisticated and largest geographical scale data provided by the 1990 U.S. Census of Transportation Planning Package. This paper uses a Geographic Information System (GIS) to measure the job/housing imbalance within a commuting catchment area having a 7-mile radius from the centroid of each Transportation Analysis Zone. Analysis of variance, stepwise multiple regression and cartographic evidence all confirm the relationship between the imbalance of jobs and housing (J/H) and mean travel time to work. This investigation highlights the fact that the imbalance between the location of jobs and housing is the most important determinant for longer commuting and suggests that higher quality housing growth close to the job-rich communities may benefit the workers to economize the commuting time.     

分析社会生态位，优化整合闽台旅游开发

“海峡两岸旅游区”是国家“十一五”优先规划和建设的重点旅游区之一。近年来,旅游业界、理论界为实现闽台旅游良性互动,进行了大胆的尝试与探索。本文从社会生态学原理的角度,分析闽台旅游资源与环境结构的同质、异质特征,并在此基础上提出优化整合闽台旅游资源,开发两岸旅游合作精品的战略思路及保障措施。     

巴音布鲁克高寒草原羊茅(Festuca ovina)群落生态位特征

为了解高寒草原羊茅群落植物生态位特征,运用Levins生态宽度指数和Cowell生态位相似性比例,对巴音布鲁克羊茅群落植物生态位宽度及生态位相似性比例进行计算.结果表明:9种植物4个资源维上羊茅的生态位宽度最大,其次为黄花棘豆、委陵菜,说明羊茅对环境的适应能力最强.生态位宽度较大的羊茅和紫花针茅与其他物种生态位相似性比例最高,说明羊茅和紫花针茅与其他物种存在着较大的资源竞争.而生态位较小的物种与其他物种生态位相似性比例较小.放牧使得羊茅群落内物种发生变化,在放牧压力持续增大的情况下,以羊茅和紫花针茅为优势种群的草原将向以黄花棘豆和委陵菜占优的退化方向演替.