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1.
Evaluating yearly net migration for the Federal Republic of Germany establishes the importance of demographic restructuring and government policies as explanations for the counterurbanization phenomenon. Counterurbanization, the spatial demographic deconcentration of regional population, is measured as an inverse relationship between the net migration rate and population sizes of functional urban regions. A counterurbanization pattern filtered-down from older to younger age-groups of the population, and appears related to an increasing preference for small-sized regions with natural amenities. For foreigners, a counterurbanization direction of movement can be explained by changes in immigration laws. While counterurbanization may be slowing down during the 1980s in certain developed countries, such as the United States, in the Federal Republic the phenomenon intensifies throughout the 1970–84 time period. Based on broad national demographic changes in combination with agespecific patterns of movement, this strong counterurbanization trend should continue well into the future. 相似文献
2.
Understanding population growth in the peri-urban region 总被引：1，自引：0，他引：1
Ford T 《International journal of population geography : IJPG》1999,5(4):297-311
This article advocates a new approach to understanding periurban population growth. A conceptual model is developed that identifies four distinct growth processes: suburbanization, counterurbanization, population retention, and centripetal migration. Each of these growth processes acts differently on particular population subgroups. The differences are reflected in variations in the spatial manifestation of periurban growth within Australia. Suburbanization process is differentiated from counterurbanization by employing three indicators of suburbanization. The first indicator includes the broad situation of the periurban destination and is defined as in-migration from the metropolitan area to adjacent, accessible periurban locations. The second indicator lies in the assessment of the commuting and social linkages with the metropolitan maintained by migrants. The third indicator is the nature of the migrants' residential destination site. Counterurbanization is largely seen to be a shift in population down the urban hierarchy to smaller centers and localities beyond the existing metropolitan boundaries. Furthermore, the article discusses the four indicators that distinguish counterurbanization from suburbanization. Another important process contributing to periurban growth is population retention. Two key indicators that lie in the measurement of increased period of residence and reduced rates of out-migration overtime characterize this process. 相似文献
3.
AMENITY MIGRATION IN THE U.S. SIERRA NEVADA* 总被引：1，自引：0，他引：1
ABSTRACT. Since 1960 California's Sierra Nevada counties have ranked among the regions with the strongest relative population growth in the state. Reassessment of peripheral areas has been the main force driving population and settlement growth in the central Sierra Nevada of California and Nevada, termed “amenity migration” or “counterurbanization.” This study analyzes the impacts of amenity migrants—“urban refugees”—on socioeconomic conditions in high‐mountain regions. We define these regions as the “High Sierra,” comprising zones at elevations more than 1,800 meters above sea level. People who migrate to the High Sierra tend to be white and well educated, with considerable household earnings. Unlike the population in the foothills, these migrants are not senior citizens. Their demand for periodic or permanent residences has caused housing prices to increase enormously. As a result, a majority of homes are now priced well beyond the reach of local salaries, which may lead to potential conflict between locals and newcomers. The massive settlement expansion in high‐mountain areas requires a new approach to land‐use planning, one that takes functional regions into account. Therefore, it is expedient to reassess existing jurisdictional boundaries. 相似文献
4.
幂次法则是一个普遍存在于自然科学与社会科学界的现象,在都市体系中亦可观察到此一现象。过去的文献仅仅对于幂次法则现象进行了观察和解释,并未能完整地解释其形成的机制。本研究尝试由复杂理论中“递增报酬”的观念来探讨幂次现象的成因,采用计算机程序来仿真都市聚落体系形成的过程,并观察递增报酬与幂次现象之关系。该仿真包含了3 种不同的区位发展吸引模式,分别为相邻关系、规模吸引以及同时考虑规模与相邻的混合模式。计算机仿真显示：① 规模吸引与混合两种模式比相邻吸引模式能够更好地解释都市聚落的成长;② 依照递增报酬法则而仿真形成的都市聚落,与幂次现象呈高度相关。随后的数理仿真演算显示,幂次法则为一统计上的普遍现象,但在递增报酬等经济因素驱动下的都市聚落体系结构与真实的状况较为吻合。因此我们推测,递增报酬极可能是形成真实世界幂次现象的机制之一。 相似文献
5.
中国乡村长寿现象与人居环境研究——以湖北钟祥为例 总被引：2，自引：0，他引：2
乡村长寿现象与人居环境的关系,是地理学与相关学科关注的课题。本文基于人文地理学与人居科学、环境科学和乡村社会等多学科视野,根据世界长寿之乡和中国百岁老人的分布规律,阐述了乡村长寿现象的涵义,分析了客观存在的乡村长寿现象及其成因。同时,以湖北钟祥为案例,运用模糊评价法、综合评价法和比较研究法,系统考究了乡村长寿现象与优越自然生态环境、和谐人文社会环境以及舒适人工居住环境的关系,归纳了乡村长寿现象的客观必然性和成因的综合性、长寿与人居环境的正相关性、山区与平原乡村长寿现象的同质性以及人类诉求健康长寿的永恒性等五个可供思考的重要命题,并对建设有利于"居民健康长寿"的乡村人居环境提出了相关政策建议。 相似文献
6.
人口老龄化城乡倒置现象是中国全面建成小康社会中面临的严峻挑战。文章利用GIS空间聚类、多元逐步回归等模型,在省域尺度上分析中国人口老龄化城乡倒置现象的时空演变特征及驱动机制。结果表明：1）时序演化方面,随着中国人口老龄化水平不断提高,其城乡倒置的现象也日趋显著。2）空间格局演化方面,1995—2018年,城乡倒置现象的空间集聚强度总体呈“低—高—低”的倒U型变化趋势。其首先出现在东部沿海地区,随后逐渐向中西部扩张,最终演化成为全国性的普遍现象。3）驱动机制方面,人口老龄化城乡倒置现象背后存在着复杂多维、非线性的交互作用机制。其中,人口和经济因子是该现象的主要驱动因子。对于经济欠发达、人口流出较为严重、农村老龄化水平较高的西部省份,其农村地区“又老又穷”的现象已经成为其乡村振兴、精准扶贫等战略实施过程中的关键挑战。 相似文献
7.
江陵地区全新世早期人类活动的孢粉记录 总被引：6，自引：3，他引：3
江陵剖面沉积物孢粉提供全新世早期人类活动的证据。早期人类活动始于6 200 a B.P.,人类大规模活动始于3 400 a B.P.。随着定居点扩大和人类活动加强,地表土壤侵蚀严重,入湖的陆源粗颗粒物质和营养物质增多。湖泊沉积物表现为粗颗粒含量迅速增加,各粒径波动频繁,TOC、TN和C/N的高值以及有机质δ13C的低值。2 500 a B.P.以后,沉积环境发生了显著变化,由湖泊及湖沼堆积转化为洪水漫滩堆积,气候变干,人类逐渐撤离该地区。 相似文献
8.
Tsoar et al. [Tsoar, H., Blumberg, D.G., Stoler, Y., 2004. Elongation and migration of sand dunes. Geomorphology 57, 293–302.] reported that seif dunes in the western Sinai Desert did not migrate laterally between 1973 and 1999. If the planform sinuosities of the dunes are removed by filtering, spatial averaging, or linear regression, however, it is evident that the dunes did, in fact, migrate laterally roughly 13 m during this 26-year period. The measured migration distance is 1–2 orders of magnitude greater than the rms co-registration error Tsoar et al. determined for the first and last air photos that were used to map the dunes. The western Sinai dunes provide another example demonstrating that linear dunes can migrate laterally, and they illustrate some of the difficulties in documenting systematic lateral motion.Lateral migration of a dune can be important geologically or geomorphologically, even where migration is too slow to detect from repeated topographic surveys. This article explains the wind conditions for the lateral migration of seif dunes in western Sinai and the possible wind occurrences that would not lead to such a migration. 相似文献
9.
Maria Fajer Jan Maciej Waga Mariusz Rzetala Artur Szymczyk Ma?gorzata Nita Robert Machowski Martyna A. Rzetala Marek Ruman 《Journal of Paleolimnology》2012,48(4):651-667
Jezioro Lake is the only natural lake in southern Poland outside mountainous areas to have existed continuously since the Pleistocene. The record of environmental change in the Late Vistulian (Weichselian) and Holocene is preserved in the deposits and landforms around the lake. This paper presents the results of paleogeographical and paleoecological research that emabled us to reconstruct the history of the Jezioro Lake. At the end of the Vistulian period, the outlet of the lake was blocked by a parabolic dune moving in from the west. Limnic sedimentation was evident in the sediment core at all levels from the Holocene, with remains of Cladocera, Chironomidae larvae, and aquatic plants. The lake did not disappear at that time, although its area decreased by a factor of 12 by the end of the period. Paleobotanical research permitted the reconstruction of sequences of plant communities and changes in nutrient status and water level. An initial oligotrophic lake, as indicated by the presence of Iso?tes lacustris L., changed to a eutrophic lake, as indicated by the presence of Potamogeton natans L. and Nuphar sp., then the lake progressed to the present-day dystrophic lake that is surrounded by a swamp. The profile of organic deposits contains a record of environmental change at least since the Younger Dryas in southern Poland. 相似文献
10.
复合1992-2012年DMSP/OLS稳定夜间灯光等多源遥感数据和统计数据,运用多种城市规模分布理论方法,对城市用地与人口规模分布时空演变特征进行系统比较。结果表明：环渤海地区城市用地规模增长速度明显快于城市人口规模增长速度,城市人口规模分布比城市用地规模分布更为均衡;城市用地规模呈首位型分布但首位优势在减弱,城市人口规模呈位次型分布但首位优势在增强;位序迅速上升的城市主要位于山东省和河北省,位序显著下降的城市主要位于辽宁省。环渤海地区城市规模空间分布呈显著的区域差异和空间极化特征,且城市用地规模分布空间特征比城市人口规模分布更为突出。研究结论可为优化区域城市空间开发格局、促进人地系统可持续发展提供参考。 相似文献
11.
应用统计学与空间分析相结合的方法,对北疆典型残余盐土区不同土层土壤盐分的空间分布特征及其变化规律进行对比分析。结果显示,随着土层深度的增加土壤盐分依次增大,底聚现象比较明显;30cm以下土壤盐分相关性较强,土壤母质等结构性因素成为影响土壤盐分空间变异的主导因素;表层土壤盐分之间的自相关距明显大于中、底层;随着土层深度的增加,土壤盐分间的Moran’s I系数增大,高-高聚集区域明显增大,主要集中在荒地区域。该研究结果将为北疆残余盐土区域土壤盐渍化改良及农业管理提供理论依据。 相似文献
12.
在区域经济中,交通是联系地理空间和区域经济活动的纽带,交通的发达程度决定了各地理单元空间相互作用的广度与深度.针对不同交通模式赋以不同的权重,基于最短加权交通网络,提出新的空间权重矩阵构建方法,构建了交通网络空间权重,与各种传统空间权重一起,对比研究甘肃省各县域单元之间的区域经济的空间相关性.研究结果表明,利用交通网络空间权重生成的空间权重矩阵,能更真实地反映区域间实际的空间过程;甘肃省的区域经济具有空间相关性但不显著,核心城市经济外溢现象不明显. 相似文献
13.
国外商业绅士化研究进展及其对本土研究的启示 总被引：1，自引：0，他引：1
商业是城市中最活跃,并且对城市发展和空间重构产生重要影响的功能之一。近20年来,随着产业转型与城市更新实践,日益突出的商业绅士化现象愈发引起国外学术界关注。同时,多源数据和定量分析方法的利用,促进了商业绅士化专题研究逐渐增多。商业绅士化的发生背景、表现特征、推动主体与形成机制,以及商业绅士化导致阶层置换、加深种族隔离等社会空间效应是主要的研究内容。通过对国外商业绅士化研究文献的梳理,以期展示城市商业高档化重构的机理以及绅士化演进的复杂性。基于当前我国城市转型和消费转型的特征与趋势,尝试提出对商业绅士化本土研究方向和方法的启示。 相似文献
14.
Analysis of data collected between 1950 and 1995 in the state of Indiana indicates that the state experiences an average of nearly 19 tornadoes each year, which occur on approximately 8 or 9 days during an average year. Analysis of storm dimensions indicates that the annual probability of a point location in Indiana being impacted by a tornado is 1.4 × 10-4 per year. The largest number of the more intense tornadoes (F2 and higher) typically occur from March to June, during the afternoon and evening, although tornadoes have been observed in each month of the year and each hour of the day. Inter-annual variability of tornadic events in Indiana is large and may reflect both physical causes (e.g., the variability of cyclone passages or jet stream location) and recording bias (e.g., increased public awareness during the 1950s). Using the data set from Indiana, statistical analyses of the temporal and spatial variability of tornadoes are undertaken. Analyses of tornado reports by county indicate that, in addition to area and population, surface roughness is a significant determinant of event frequency. Analyses presented herein also indicate that in contrast to previous studies, (1) no statistically significant hebdomadal cycle of tornado reporting is evident in the data and (2) the diurnal cycle of tornado records is evident for all F-scale classes and is not confined largely to the weak tornado categories. Analyses of the physical dimensions and F-scale ratings of tornadoes in Indiana indicate that there has been a decline in reported tornado intensity, width, and length between 1950 and 1995. These changes are in accord with evidence of a decreasing number of reports of strong and violent tornadoes across the United States over this period and appears to be principally a result of reporting biases at the beginning of the record. [Key words: tornado climatology, temporal and spatial variability, reporting bias.] 相似文献
15.
H. Jesse Walker 《自然地理学》2013,34(4):373-375
The focus of this research is the development of a model which explains channel pattern variability in streams. Since channel pattern is commonly regarded as a qualitative phenomenon, the research employs a logistic regression model, which is advocated as an alternative to traditional graphic/discriminant analysis, since the concepts of threshold and instability have very natural expressions in the logistic regression framework. The results demonstrate that channel gradient and mean discharge can effectively explain channel pattern (i.e., whether the channel is single or multithreaded) in an environment where there is a small range of bed material size. Sediment sorting is also shown to be related to channel pattern in the study environment. Models using valley gradient rather than channel gradient are shown to be distinctly inferior, and no advantage is found in using a stream power measure as opposed to separate gradient and discharge measures. [Key Words: fluvial geomorphology, stream channels, channel patterns, models.] 相似文献
16.
The human role in changing river channels 总被引：12，自引：3，他引：12
Direct consequences of the human role, where human activity affects river channels through engineering works including channelization, dam construction, diversion and culverting, have been long recognised Marsh, 1864 and Thomas, 1956. The less obvious indirect effects of point and reach changes occurring downstream and throughout the basin, however, are much more recently appreciated, dating from key contributions by Strahler [Strahler, A.N., 1956. The nature of induced erosion and aggradation. In W. L. Thomas (Ed.), Man's Role in Changing the Face of the Earth. University of Chicago Press, Chicago, 621–638.], Wolman [Wolman, M.G., 1967. A cycle of sedimentation and erosion in urban river channels. Geografiska Annaler 49A, 385–95.], Schumm [Schumm, S.A., 1969. River metamorphosis. Proceedings American Society of Civil Engineers, Journal Hydraulics Division 95, 255–73.], and Graf [Graf, W.L., 1977. The rate law in fluvial geomorphology. American Journal of Science, 277, 178–191.]. These are complemented by effects of alterations of land use, such as deforestation, intensive agriculture and incidence of fire, with the most extreme effects produced by building activity and urbanisation.Changing river channels are most evident in the channel cross-section where changes of size, shape and composition are now well-established, with up to tenfold increases or decreases illustrated by results from more than 200 world studies. In addition the overall channel planform, the network and the ecology have changed. Specific terms have become associated with changing river channels including enlargement, shrinkage and metamorphosis. Although the scope of adjustment has been established, it has not always been possible to predict what will happen in a particular location, because of complex response and contingency. The ways in which changes in cross-section relate to reach and network changes are less clear, despite investigations showing the distribution of changes along segmented channels.When considering the human role in relation to changing river channels, at least five challenges persist. First, because prediction of the nature and amount of likely change at a particular location is not certain, and because the contrasting responses of humid and arid systems needs to be considered, modelling is required to reduce uncertainty, as was first emphasised by Burkham [Burkham, D.E., 1981. Uncertainties resulting from changes in river form. American Society Civil Engineers Proceedings, Journal Hydraulics Division 107, 593–610.]. Second, feedback effects incorporated within the relationship between changes at channel, reach and network scales can have considerable implications, especially because changes now evident may have occurred, or have been initiated, under different environmental conditions. Third, consideration of global climate change is imperative when considering channel sensitivity and responses to threshold conditions. Fourth, channel design involving geomorphology should now be an integral part of restoration procedures. This requires, fifthly, greater awareness of different cultures as a basis for understanding constraints imposed by legislative frameworks. Better understanding of the ways in which the perception of the human role in changing river channels varies with culture as well as varying over time should enhance application of design for river channel landscapes. 相似文献
17.
18.
珠三角快速城镇化地区发展的增长与收缩新现象 总被引：8，自引：2，他引：6
珠江三角洲是世界范围内经济和城镇发展“增长奇迹”的典型地区,当中以东莞为代表的“外向型城镇化”模式长期受到国内外学者的关注。然而,2008年的金融危机冲击对东莞经济造成巨大冲击,市域范围同时出现了普遍增长与局部收缩两种截然不同的新空间现象。随着中国经济步入新常态,城镇化快速发展过程中伴随的局部收缩现象逐渐引起学界和社会的广泛讨论。基于此,从城镇发展要素的集聚与流动出发,结合经济、人口和用地三个维度,提出理解城镇增长与收缩的分析框架,并对不同类型特征的城镇进行区分：持续增长、转型增长、潜在收缩与显著收缩。在实证分析部分,文章以东莞为案例,通过考察各镇街单元城镇增长与收缩的时间演变和空间格局,结合典型城镇案例分析,从经济危机冲击、刘易斯转折点、路径依赖存在、制度环境安排四个方面探讨东莞城镇增长与收缩的形成机制,最后对增长与收缩的未来深化研究方向进行讨论。 相似文献
19.
厄尔尼诺事件的强度与登陆广东热带气旋数量的关系初探 总被引：5，自引：1，他引：4
文章对厄尔尼诺事件的强度与登陆广东的热带气旋数量之间的关系进行初步的了统计分析。结果表明: 就总的厄尔尼诺年份来看, 厄尔尼诺事件对登陆广东的热带气旋总数量没有显著的影响;但就具体的厄尔尼诺事件的强度来看, 强、中和弱的厄尔尼诺事件都对登陆广东的热带气旋有明显的影响, 只是强和弱的厄尔尼诺事件使登陆广东的热带气旋数量比非厄尔尼诺年份明显偏少; 而中等厄尔尼诺事件却使登陆广东的热带气旋数量比非厄尔尼诺年份偏多。厄尔尼诺通过影响沃克环流,使沃克环流随着厄尔尼诺强度的不同而产生不同幅度的东移,进而使登陆广东的热带气旋源地的气流出现不同情况,最后影响登陆广东的热带气旋的数量。 相似文献
20.
W.P. Adams J.G. Cogley M.A. Ecclestone & M.N. Demuth 《Geografiska Annaler: Series A, Physical Geography》1998,80(1):37-50
Baby Glacier, Axel Heiberg Island, N.W.T., Canada is a small (0.6 km2 ), high-latitude (79°N), high-altitude (700–1200 m) glacier with a mass balance record extending from 1959–60 to the present. The record demonstrates shrinkage of the glacier, but a statistically significant trend is not evident. Correlations are strong between the mass balance of Baby Glacier and that of the nearby and much larger White Glacier, and also those of even larger, more distant glaciers. Thus programmes of measurement on small, simple ice bodies such as Baby Glacier can be representative of a large region. However, inter-annual changes are more accentuated for Baby Glacier. Baby Glacier does not meet all of the usual criteria for a representative glacier, but it straddles the regional equilibrium zone, a fact which helps to offset the disadvantages of its small size and limited altitudinal range. The equilibrium zone deserves to be an important focus for studies of high-arctic mass balance, with the aim of facilitating future measurement programmes which will rely on satellite remote sensing. 相似文献