Understanding Urban Vitality from the Economic and Human Activities Perspective:A Case Study of Chongqing,China

The literature on urban vitality tends to focus on the built environment.This paper argues that some important processes in shaping vitality may be overlooked without examining the intensity and diversity of economic and human activities.Using newly developed spatial big data and adopting the methods of multi-indicator measurement and spatial analysis methods,we analyzed the pattern of urban vitality in Chongqing,a provincial city in western China and,on this basis,evaluated the creation and maintenance of urban vitality from the economic and human activities perspective.Our findings indicate that the impacts of economic and human activities are positive and significant.Among the three intensity and diversity indicators,economic intensity and population density show an effect on urban vitality stronger than that of economic diversity.However,economic diversity has the strongest superposition or interactive effect,and is thus an important foundation dynamic.The positive effect of population density on urban vitality is largely a result of Chongqing’s jobs-housing balance.The case of Chongqing highlights the importance of topographic features,historical inheritance,large-scale migration,and cultural activities in shaping the distinctive vitality pattern of a city.This study contends that the creation and maintenance of urban vitality can not be fully explained without incorporating the impacts of economic and human activities.It contributes to a comprehensive measurement of urban vitality and enriches its connotations.

Trade-offs between prosperity and urban land per capita in major world cities

Globally,urban land expands at a faster rate than the corresponding urban population,which comes at a cost of agricultural and natural land.Wealth has been identified as an underlying driver of this trend,but it is unclear whether more prosperous cities inevitably have a greater urban land consumption.Here,we map urban pros-perity indicators to their relevant Sustainable Development Goals(SDGs)for 64 major world cities and relate these to the corresponding urban land consumption(defined here as built-up land per capita).Results indicate a moderately-weak but significant correlation between overall prosperity and urban land consumption(Spear-man’s correlation,𝜌ρ=0.47,p<0.001),suggesting a trade-offbetween both.In addition,we find a regional clustering,with for example cities with relatively low prosperity and low urban land consumption in Africa,and cities with high prosperity and low-to-medium urban land consumption in Europe.The moderately-weak correlation in combination with these regional differences suggests that the observed trade-offis avertable and that other drivers moderate this relation.Consequently,cities can increase their prosperity without additional environmental consequences entailing land take and the conversion of natural and agricultural land.

Spatial Autocorrelation and Localization of Urban Development

A nonlinear analysis of urban evolution is made by using of spatial autocorrelation theory. A first-order nonlinear autoregression model based on Clark’s negative exponential model is proposed to show urban population density. The new method and model are applied to Hangzhou City, China, as an example. The average distance of population activities, the auto-correlation coefficient of urban population density, and the auto-regressive function values all show trends of gradual increase from 1964 to 2000, but there always is a sharp first-order cutoff in the partial auto- correlations. These results indicate that urban development is a process of localization. The discovery of urban locality is significant to improve the cellular-automata-based urban simulation of modeling spatial complexity.

Spatio-Temporal Changes of Population Density and Urbanization Pattern in China(2000–2010)

Population distribution and their temporal variation are a direct proxy of urbanization. This study evaluates the population density variation of China between 2000 and 2010 at the township level by using the data of the fi fth and sixth national population censuses. The urbanization patterns of China in 2000 and 2010 are depicted based on the population densities at various levels and the urbanization process of China between 2000 and 2010 is then analyzed through a comparative approach. It also tries to visualize the population density dynamics and urbanization pattern variations of China at the township level.

Supply-Demand Analysis of Urban Emergency Shelters Based on Spatiotemporal Population Estimation

Supply–demand analysis is an important part of the planning of urban emergency shelters.Using Pudong New Area,Shanghai,China as an example,this study estimated daytime and nighttime population of the study area based on fine-scale land use data,census data,statistical yearbook information,and Tencent user-density big data.An exponential function-based,probability density estimation method was used to analyze the spatial supply of and demand for shelters under an earthquake scenario.The results show that even if all potential available shelters are considered,they still cannot satisfy the demand of the existing population for evacuation and sheltering,especially in the northern region of Pudong,under both the daytime and the nighttime scenarios.The proposed method can reveal the spatiotemporal imbalance between shelter supply and demand.We also conducted a preliminary location selection analysis of shelters based on the supply–demand analysis results.The location selection results demonstrate the advantage of the proposed method.It can be applied to identify the areas where the supply of shelters is seriously inadequate,and provide effective decision support for the planning of urban emergency shelters.

Effects of urbanization on heavy metal accumulation in surface soils, Beijing

Urbanization processes affect the accumulation of heavy metals in urban soils. Effects of urbanization on heavy metal accumulation in soils were studied using Beijing as an example. It has been suggested that the ecological function of vegetation covers shifting from natural to agricultural settings and then to urban greenbelts could increase the zinc（Zn） concentrations of soils successively. The Zn concentration of urban soils was significantly correlated to the percentage of the impervious land surface at the500 m × 500 m spatial scale. For urban parks, the age or years since the development accounted for 80% of the variances of cadmium（Cd） and Zn in soils. The population density,however, did not affect the heavy metal distributions in urban soils. To conclude, the urban age turned out to be a notable factor in quantifying heavy metal accumulation in urban soils.

Impact of spatiotemporal land-use and land-cover changes on surface urban heat islands in a semiarid region using Landsat data

Many factors are involved in urban heat island development,such as lack of green spaces,improper choice of building materials,densification,and other human activities.The aim of this research was to quantify the effects of land-use/land-cover(LU/LC)changes on urban land surface temperature(LST)during a 25-year period(1993–2018)for the semiarid Shiraz City in southern Iran using Landsat data(TM,ETM+,and OLI/TIRS)and machine learning algorithms.Five main LU/LC classes,such as orchard,vegetation,bare surface,asphalt cover,and built-up areas,were identified using a support vector machine algorithm.Landsat images were used to retrieve normalized difference vegetation index(NDVI)and normalized difference built-up index(NDBI).The results showed that the mean LST over the entire study domain increased considerably between 1993 and 2018,due to urbanization,decrease of green areas,and increasing industrial areas.Built-up areas increased considerably by 25.8%from 80 to 100.6 km^(2) between 1993 and 2018,while vegetation cover decreased dramatically by 69.3%.Mean LST increased from 38.4 to 40.2℃ during the 25-year period with a significant increase of 3.9℃ between 2013 and 2018.In addition,the Urban heat island Ratio Index(URI)displayed a substantial upward trend during the 25-year period.

New urban map of Eurasia using MODIS and multi-source geospatial data

Urban areas are of paramount significance to both the individuals and communities at local and regional scales.However,the rapid growth of urban areas exerts effects on climate,biodiversity,hydrology,and natural ecosystems worldwide.Therefore,regular and up-to-date information related to urban extent is necessary to monitor the impacts of urban areas at local,regional,and potentially global scales.This study presents a new urban map of Eurasia at 500 m resolution using multi-source geospatial data,including Moderate Resolution Imaging Spectroradiometer(MODIS)data of 2013,population density of 2012,the Defense Meteorological Satellite Program’s Operational Linescan System(DMSP-OLS)nighttime lights of 2012,and constructed Impervious Surface Area(ISA)data of 2010.The Eurasian urban map was created using the threshold method for these data,combined with references of fine resolution Landsat and Google Earth imagery.The resultant map was compared with nine global urban maps and was validated using random sampling method.Results of the accuracy assessment showed high overall accuracy of the new urban map of 94%.This urban map is one product of the 20 land cover classes of the next version of Global Land Cover by National Mapping Organizations.

POPULATION EXPANSION IN CHINA'S METROPOLISES AND ITS SCALE-CONTROL

Metropolises are centers of politics, economy, culture and information, and also economic growth poles in comparatively large areas. After 1949, China’s urban structure have changed greatly, from original 'pyramid' shape into 'upside -down pyramid' shape, that is, more megalopolises and metropolises, fewer medium-sized and small cities. The most distinguishing feature of urban population growth was the remarkable increase of population in megalopolises and metropolises. The key reason for urban population expansion is to want to obtain the benefits of scale -agglomeration economy of metropolises. The number of urban functions directly determines the quality and quantity of urban population. Metropolises appeal not only agricultural population but also the population of medium-sized and small cities, which put much more population pressure on metropolises. The ideal goals of scale-control of metropolitan population are discussed in terms of economy, society and ecollogy. In order to control the

利用城市标度律分析广西城市要素与人口规模发展

利用城市标度律理论,从全域和城市(镇)群2个视角定量分析了广西城市发展过程中城市要素和人口规模间的标度关系。研究结果表明:在广西全域视角下,城市要素与人口规模呈线性关系,但在市辖区尺度下的城市要素更能满足城市人口的增长需求。广西的城市发展水平要低于全国其他城市发展水平,标度因子呈现负值的要素与经济相关,特别是地区生产总值的增长幅度与人口的增长规模不匹配,人口红利无法转化为经济增长点。在城市(镇)群视角下,广西各城市(镇)群的城市发展具有显著的空间分异性特点。政府应根据每个城市或地区的特点来指导城市更好地发展与扩张,加强各城市(镇)群之间的联系,构建更加全面、健康、可持续的城市发展战略。

城市人口密度、房价与城乡消费不平等

城乡消费不平等直接影响着共同富裕目标的推进与新发展格局的构建。城市人口密度和房价是扩大内需的重要因素。本文在构建数理模型的基础上,利用2011—2020年中国省级面板数据实证检验了城市人口密度和房价对城乡消费不平等的影响,结果表明城市人口密度和房价会分别对城乡消费不平等产生显著的抑制和促进作用,这一结果在稳健性检验和内生性讨论后仍然成立。分位数回归、考虑消费结构和分组回归后的结果表明城市人口密度和房价对城乡消费不平等的影响存在显著的异质性差异。作用机制检验和调节效应分析结果表明城乡收入不平等是城市人口密度影响城乡消费不平等的作用机制,财富效应和物价是房价影响城乡消费不平等的作用机制。缩小平均家庭户规模、增加中规模家庭户比重以及降低大规模家庭户比重都能够通过调节效应抑制城乡消费不平等水平的扩大。本文丰富了相关领域的研究,为缩小城乡消费不平等及扩大内需提供了政策启示。

高密度城区绿地景观格局对PM_(2.5)/O_(3)的多尺度影响

为探究高密度城区绿地景观格局对于PM_(2.5)浓度与O_(3)浓度的尺度效应,分析西安市高密度城区范围,选取边界密度(ED)、景观形状指数(LSI)、面积加权形状指数(SHAPE_AM)和平均形状指数(SHAPE_MN)共4个景观格局指数衡量绿地景观格局,爬取2020—2021年国家空气质量监测站点的大气监测数据,运用皮尔逊相关性分析和线性回归分析方法,探究多尺度下高密度城区绿地景观格局对PM_(2.5)和O_(3)的时空分布特征、绿地景观格局特征和PM_(2.5)浓度、O_(3)浓度与景观格局指数的多尺度影响关系.结果表明,景观格局在夏季对于PM_(2.5)浓度、在春季对于O_(3)浓度的影响更为显著;在高密度城区内较小尺度的绿地上优化景观格局对PM_(2.5)与O_(3)浓度影响更有效.由此提出的绿地优化策略可为城市高密度城区多尺度绿地规划设计提供参考依据.

城市土地扩张和人口增长的关联——长期趋势与影响因素

城市土地扩张快于人口增长导致城市低密度增长,但其宏观变化趋势及其与社会经济发展阶段的关系仍不明确,从宏观时空尺度揭示城市人口密度变化规律,对可持续城市发展决策具有重要意义。本文以工业革命以来典型发达国家和改革开放以来中国的城市发展为研究对象,结合经济发展、产业发展、城镇化水平和交通变革等因素,研究发现:(1)工业化以来,典型发达国家城市人口密度多先上升后下降,拐点在城镇化率50%~70%、工业化完成后、汽车产业发展到一定规模时出现;(2)改革开放后,中国城市人口密度总体上先上升后下降,工业化前期时城市人口密度下降现象已经出现;(3)当前全球城市人口密度下降具有趋势性,但中国城市人口密度下降幅度较大、速度较快,城市人口密度拐点出现相对较早。我国当前阶段城市用地需求多元增长、城市交通汽车化发展等是城市土地扩张的重要驱动力,管控城市扩张速度、促进城市可持续发展转型具有紧迫性。

人群时空行为与城市昼夜人口空间集聚分析--以武汉市为例

城市是人口和资源在时空上的聚集,昼夜人群空间集聚是其中最基本、最主要、最频繁的人口时空变化模式,是理解城市复杂演变的基础微观机制。由于缺乏先进的技术手段,往往无法真实地记录和量测城市人口的个体流动与整体趋势,人们对城市昼夜人口空间集聚的了解仍然十分有限。本文基于城市人群时间地理特征,从城市大数据中挖掘并模拟城市人群的社会时空行为,在此基础上计算并分析城市昼夜人口集聚时空分布。对武汉市主城区的昼夜人口集聚分析表明:①人口密度与分布面积具有幂律关系,符合Clark模型;②傅里叶变换可有效地揭示人口分布空间变化的主方向和延伸程度;③中心城区夜间人口较白天人口分布更为集聚,研究区昼夜间人口流动主要以城区内部流动为主。归纳出城市昼夜人口集聚差异具有5种模式:交通线、三明治、光晕、椒盐和单体模式,这些模式与城市演化及空间格局有密切关系,其中交通线模式是研究区人口昼夜差异最大的一种模式。

城市人口规模、就业密度与生产性空气污染排放——双重倒“U”型关系的解析与检验

随着中国城镇化快速推进,城市生产活动的活跃引致空气污染排放的加剧,明晰城市人口规模和就业密度对生产性空气污染排放的影响效应意义深远。该研究通过构建理论模型开展数值模拟,发现城市人口规模、就业密度与城市生产性空气污染排放之间均满足倒“U”型关系,且规模与密度均对倒“U”型门槛值存在调节效应。基于此,利用2010—2018年中国274个地级以上城市的面板数据进行实证检验,估计结果表明:①城市人口规模、就业密度对生产性空气污染排放的影响均符合稳健的倒“U”型特征,2018年生产性空气污染排放由升转降的规模门槛值和密度门槛值分别为105万人和3469人/km2。②目前,中国部分城市的人口规模与就业密度已超过门槛值,步入生产性空气污染排放的“双下行”通道,这些城市人口增加延长了非生产时间,对有效劳动供给造成的损失超过劳动力时间禀赋的增加,从而使得生产受限减少了生产性空气污染排放;同时,城市高就业密度有利于创新扩散和知识外溢,对生产性空气污染排放产生的减排作用强于高就业密度带来的生产激励效应对空气污染排放的增排作用,这些作用的综合结果使得生产性空气污染排放趋于下降。③城市人口规模扩张有助于降低密度门槛值,城市就业密度的提升也有助于降低规模门槛值。人口规模的扩张能够为知识外溢等提供有利条件,促使密度门槛前移;而就业密度的提升则会产生一定的拥挤效应,使得非生产时间更快增长,生产扩张提前受限,促使规模门槛前移。以上结论对推进新型城镇化与高质量发展具有启示意义。

清代贵州区域人口与城镇地理分布

贵州人口城镇化不平衡格局主要受喀斯特地貌环境等自然条件制约,也与省内各区域开发程度差异、城镇数量和密度等经济地理因素密切相关。由清代贵州人口规模和密度的区域差异入手,探讨清代城镇数量、密度以及等级地位的区域分布,分析城镇分布与人口、移民、历史建置、经济开发及民族形势等区域地理要素的内在关系,可加深对贵州人口分布与城镇化格局的演变过程的理解,为今后贵州制定人口发展和城镇化政策提供一定的历史依据作参考。

长三角城市公园与人口密度的标度律分析

城市公园配置不均衡与人口高度聚集是长三角城镇化进程中面临的重要问题之一,深刻把握城市公园与人口密度之间的客观规律,有利于探明与人口聚集状态相协调的公园建设路径。文章选用2020年长三角城市公园和人口密度相关指标截面数据,引入标度律模型,探析二者在长三角城市的标度律。结果表明:(1)整体标度律特征方面,公园与人口密度存在非线性关系,其中,公园率、人均公园面积呈超线性模式,为集聚效应的体现,公园密度呈次线性模式,具有规模效应;(2)分类标度律特征方面,苏、浙、皖三省与不同人口密度城市公园要素均符合长三角整体标度律,并存在趋同聚集的空间规律。研究结论可为适配城市人口密度的公园建设提供科学指导,亦是标度律在城市可持续发展层面的应用延伸。

黄河流域城镇化对地下水的影响分析

黄河流域是我国重要的生态屏障,也是我国粮食作物的主要产区。近年来,随着城镇化的发展,当地水资源分配出现了显著变化。因此,厘清黄河流域城镇化作用下水循环的改变对制定黄河流域城镇化政策具有重要意义。本文利用资源环境科学与数据中心的黄河流域下垫面数据、世界人口数据集的人口密度和Gravity Recovery and Climate Experiment(Grace)的Center for Space Research(CSR)陆地总水储量格点数据,开展了黄河流域城镇化过程中地下水的变化特征分析工作。结果表明:黄河流域城镇化程度具有显著的空间差异,下游存在明显的城镇化加剧现象;全域人口密度整体呈上升趋势,其中下游的人口增长趋势最大;黄河流域的地下水呈下降趋势,以下游的地下水下降最为显著。通过对比黄河流域新增城镇、不变城镇和消失城镇的地下水变化差异,发现地下水下降幅度最小出现在消失城镇,新增城镇的地下水下降幅度小于不变城镇的区域。因此,黄河流域城镇化对地下水的减少具有显著的作用,新增城镇地下水并没有出现显著下降的结果也说明近年来城镇化后的地下水保护政策取得的效果良好。

长三角城市绿地标度因子的时空特征分析

【目的】深入解析长三角城市绿地与人口的关系,对于推进区域一体化背景下的新型城镇化建设具有重要意义。【方法】引入标度律模型,选取长三角41个城市为研究单元,分析2000—2020年城市绿地要素的标度因子时空特征。【结果】1)全域特征方面,长三角城市绿地面积由超线性演化为亚线性模式,公园绿地、公园面积处于亚线性模式,规模效应显著,城市绿地各要素的增长模式均受建成区面积亚线性模式的约束。2)城市绿地要素的标度因子比较方面,呈现“公园绿地面积>城市绿地面积>公园面积”状态,公园绿地面积的标度因子略高于城市绿地面积,趋近于线性增长模式,公园面积标度因子的亚线性模式最明显,三者标度因子较全国水平均较低。3)空间分异特征方面,城市绿地要素标度因子在省级行政区划上呈“江苏>浙江>安徽”的状态;在时序演化规律上,三省标度因子逐渐趋近,亚线性模式的共性特征日趋明显。【结论】研究揭示了城市绿地的规模效应及其标度因子的时空特征及其内在规律,以期为统筹区域城市绿地与人口的协调发展提供科学依据。

论习近平以人为核心城市观的内涵和创新价值

习近平以人为核心的城市观是对以人为本的科学发展观的继承和发展,是人民中心思想的体现。针对以土地经济为核心的城镇化导致的城乡差距拉大、城市人口过密、交通拥堵、环境污染等问题,要求从经济社会全局考虑城镇化,以人口城镇化促进社会公平,降低城市人口密度,关注安全、健康、便利,把城市建设成为宜业宜居、舒适便利的高品质生活空间。强烈的、与时俱进的问题意识,重点突出、全面协调的问题解决方法,充分发挥市场在资源配置上的决定性作用和政府的职能,追求高品质生活空间,注重城市规划建设治理全过程的民主参与,是习近平城市观的创新之处和鲜明特色。