A basic assessment of residential plant diversity and its ecosystem services and disservices in Beijing,China

About 52% of the world's population now lives in urban areas, and 41% of urban land in developed countries is used for residential areas. The amount and quality of residential green space, an important element in urban residential infrastructure, is closely correlated to city dwellers' quality of life. The quality of green spaces is not only closely correlated to the ecosystem services they provide, but also to their disservices. In order to (i) examine how plant diversity and plant traits vary in different residential areas, (ii) determine the main socio-economic factors driving plant trait variations across different residential areas, and (iii) provide an overview on selected ecosystem services and disservices related to plant diversity, we investigated the flora and socio-economic properties of 83 residential areas in Beijing, China. We found a total of 369 plant species belonging to 99 families and 150 genera. With respect to plant traits, there were 90 annual species, 174 alien species, 169 pollen allergenic species, and 133 species with edible or pharmaceutical value. The number of perennial, alien, ornamental and edible plant species was largest in residential areas completed in the 1990s. The number of allergenic species was highest in residential areas completed prior to 1980. The Simpson, Shannon and Pielou indices for trees and shrubs were highest in areas completed in the 1990s, while those same indices for herbs were highest in residential areas completed prior to 1980. General Linear Model analyses revealed that richness increased with increasing housing price across all groups of species. Principal Component Analysis indicated that housing price and floor-area ratio are the variables that positively correlate with species richness for all groups of species.     

基于街景数据的建成环境与街道活力时空分析——以深圳福田区为例

建成环境对街道活力的影响是国内外城市研究的热点议题。然而,对于建成环境要素的测度与评估多偏重于二维建成环境指标,尚未充分挖掘三维建成环境指标。以深圳市福田区为例,采用街景数据、路网数据、POI数据及移动互联网位置服务数据,建立周末分时段模型,探讨商业街道和生活街道活力的时空间分布特征及建成环境对其产生的影响。结果表明：① 商业街道上居民全天活动的峰值时段为18:00~20:00,生活街道上居民全天活动的峰值时段为11:00~13:00。② 深圳市福田区街道活力总体呈现多中心结构,随时间变化显现出明显的空间差异。③ 不同的建成环境指标对街道活力的作用时段与影响程度存在差异。提高功能混合度有利于提升商业街道凌晨、上午和夜间的活力及生活街道午后和傍晚的活力;过宽的相对步行宽度对生活街道活力提升有抑制作用,更安全的步行环境对商业和生活街道夜间活力提升有促进作用;界面连续程度高的商业街道午后及夜间的活力更强,界面多样性丰富的生活街道白天活力更强。     

水热条件共同驱动新疆湿地植物丰富度空间分布格局

在地理空间尺度上,气候因素（如热量、降水量等）一直被认为是物种多样性的主要驱动因素。然而,气候因素能否解释湿地植物多样性格局仍不清楚。研究探讨了环境因素尤其水分和热量条件对湿地物种分布的影响,具体包括经度、纬度、海拔、年平均降水量、年平均气温、年平均蒸发量和年平均日照时数总计7个指标,研究对象涉及新疆3个二级流域的26处湿地公园,应用结构方程模型分析了各指标对湿地植物丰富度影响的相对大小及其相互作用关系。另外,还利用莫兰指数（Moran’s I）对各变量残差进行了空间相关性分析,以评估空间相关性的影响。结果表明：（1）结构方程模型总计解释了41.8%的物种丰富度变异,以年平均降水量对物种丰富度总效应最高,为0.47,其次是年平均日照时数,为-0.42,其中年平均降水量为正效应,年平均日照时数为负效应。其他各指标对物种丰富度的效应均不显著。（2）年平均降水量对植物丰富度的影响主要表现为直接效应,占总效应的92.86%,年平均日照时数对植物丰富度的影响主要是间接效应,占总效应的54.76%。（3）空间相关性分析表明年平均降水量和年平均日照时数的残差均不存在空间相关性,莫兰指数在-0.15～...     

Scale Dependence of Species Richness Maps*

Mapping patterns of species richness is a longstanding tradition in biogeography and more recently in conservation planning. This paper describes the effects of sampling unit size on patterns of vertebrate richness across landscapes in the Intermountain Sagebrush and Rocky Mountain Forest ecoregions in Idaho. Variability of richness decreased with increasing size of the spatial sampling units at both sites, with greater overall variability in the forested site. Richness in the sagebrush region was best explained by alpha diversity, whereas beta diversity accounted for more of the variability in richness in the forested site.     

Patterns of plant diversity in ironstone ranges in arid south western Australia

Patterns of plant diversity were examined across 24 ironstone ranges in arid south western Australia. The high levels of beta diversity displayed between ranges primarily resulted from high turnover of perennial species and was not influenced by the lower species richness on the more arid ranges. The variance in composition of the vegetation across the ranges was evenly distributed between the broad spatial pattern and environmental factors measuring climate gradients, local site variables and soil chemistry. In contrast broad scale spatial and climatic gradients were most important in explaining the variance in perennial species richness. Ranges along the boundary of the Arid Zone appear to have acted as refugia during the climatic cycles of the Tertiary with several hotspots of species endemism and taxa with distributions centered on these ranges. On the more arid ranges these specialist ironstone taxa are largely absent. The variation in richness of these specialists taxa was strongly influenced by patterns in soil chemistry in addition to the broad scale spatial and climate gradients. The concentration of the ironstone specialist taxa is largely coincidental with the most prospective areas for iron ore mining and this will provide considerable challenges in conserving these unique ecosystems.     

Patterns and dynamics of urban forests in relation to land use and development history in Guangzhou City, China

Trees in cities display a varied pattern that is often moulded by a city's physical fabric and its evolution through time. The town plan expressed in spatial dimension as land use, and in temporal sense as development history, furnishes a framework to evaluate the intricate association between city and trees. Guangzhou city, the premier metropolis of south China, has been established for 2800 years, and has a long history of urban greening and heterogeneous land use. Five urban districts, which represent old, middle-aged and young stages of development and cover the bulk of the city's built-up zones, form the study area. Interpretation of aerial photographs is used as a basis to classify the urban forest into three types, and to design a sampling scheme for studying trees in urban parks, institutional grounds and roadsides. District history has bequeathed a plethora of configurations in terms of buildings, roads and land uses, accompanied by plantable spaces of dissimilar dimensions, geometry and quality. The districts display diverse tree attributes such as frequency, density and species diversity. Young districts, with lower density, more institutional uses and wider roads, present more opportunities for greening. Recent shifts in landscape fashion have introduced a significantly different treescape. A few exceptionally large parks and institutional sites play a pivotal role in the city's tree assets. Parks, roadsides and institutional forests have different tree-stocking rates and species assemblages. Implications for future planting and management of urban trees in different situations, and for the greening of other cities in China, and other developing countries, are explored.     

Street as a big geo-data assembly and analysis unit in urban studies: A case study using Beijing taxi data

Quantitative research of urban geography has benefited greatly from the rapid development of big geo-data. Spatial assembly is an essential analytical step to summarize and perceive geographical environment from individual behaviours. Most research focuses on the methodology of how to utilize the big data, while the adopted spatial units for data aggregation remain areal in nature. This article conceptually proposes an idea of sensing cities from a street perspective, emphasizes the significance of street units in quantitative urban studies. Using a three-month taxi trajectory dataset and the major streets in Beijing, we explore the spatio-temporal patterns of urban mobility on streets, cluster streets into nine types based on their dynamic functions and capacities. Additionally, we discuss the differences and connections between the linear street unit and traditional areal units, investigate the possibility of uncovering urban communities using streets, and point out the complexity of streets. We conclude that street unit as a supplement to areal units, is able to effectively minify the modifiable areal unit problem (MAUP), sense urban dynamics, depict urban functions, and understand urban structures.     

Comments on “Automated Geography”

Mapping patterns of species richness is a longstanding tradition in biogeography and more recently in conservation planning. This paper describes the effects of sampling unit size on patterns of vertebrate richness across landscapes in the Intermountain Sagebrush and Rocky Mountain Forest ecoregions in Idaho. Variability of richness decreased with increasing size of the spatial sampling units at both sites, with greater overall variability in the forested site. Richness in the sagebrush region was best explained by alpha diversity, whereas beta diversity accounted for more of the variability in richness in the forested site.     

Patterns of alien plant invasions in northwestern Patagonia, Argentina

Invasive plant species are a growing concern in many regions of the world, yet little information is available on the effects of habitat type and distance to urban settlements on the ability of alien plants to become established. We studied plant communities from the arid steppes to the Andean forest within two national parks and surroundings, in northwestern Patagonia, Argentina. Alien and native vascular plant species were sampled using 90 × 100 m² plots and analyzed in relation to both climatic and environmental variables and distance to urban centres. We also compared life-forms of alien and native species. Precipitation and distance to an urban centre were important determinants of alien species community richness and composition, and shrubland sites had significantly more alien species than forest or steppe sites. Alien flora (15% of the species) was composed of a higher proportion of annuals and biennials than native flora. Our results suggest that precipitation, distance to source population, and anthropogenic disturbance influence the invasion process in this region, together with the availability of open niches. This work stresses the importance of monitoring invasive species in natural reserves, and of considering habitat types as well as idiosyncratic characteristics of the non-natives for developing management strategies.     

滨江城市跨江发展模式、过程及驱动机制

跨江发展是滨江城市拓展生长空间、实现跨越式发展的重要举措。在对国内外跨江发 展城市分析的基础上, 从跨江主体组织方式的视角, 探讨了城市跨江发展的一般模式和过程, 分析了城市跨江发展的影响因素和驱动机制。研究表明:(1)城市跨江发展可分为独立跨越、 组合跨越、兼并跨越和联合跨越四种模式, 其中, 独立跨越和兼并跨越是我国较为常见的两 种跨江发展模式; (2)城市跨江发展一般经历初始、生长、加速发展和稳定发展四个阶段。 小江河流域城市的跨江发展为渐进过程, 多为城市自组织结果, 而大江河流域城市的跨江发 展主要集中在加速发展期, 多为他组织结果;(3)城市跨江发展受自然、经济、社会、政治、 科技等多种因素影响; (4)跨江发展过程受需求力、保障力、引导力和驱动力等共同驱动, 其中, 政策引导下的体制创新、区划调整下的空间整合、园区带动下的区域发展、交通引导 下的空间组织是当前城市跨江发展最为重要的引导和驱动因素。     

The role of local land-use on the urban heat island effect of Tel Aviv as assessed from satellite remote sensing

Climate change in cities has received much focus in the past few decades. Heat stress in urban areas has an adverse effect on human health and is expected to worsen in the future due to the global warming. Vegetation has been shown to mitigate this effect, but introducing ‘green’ areas into the metropolitan space is a challenging task. We assessed the thermal load in terms of surface temperature in Tel Aviv, the biggest metropolitan area of Israel. The thermal effect of four different urban land uses was estimated. Specifically, we compared the cooling effect of residential areas with high vegetation cover (referred here as ‘green’ residential) to that of small to medium size (2–40 ha) public parks. To this end, we used satellite data of land surface temperature (LST) and the Normalized Difference Vegetation Index (NDVI), as a surrogate for vegetation cover. High-temporal data were combined with high spatial resolutions data to produce 10-year average LST and NDVI maps at high spatial resolution over Tel Aviv. As expected, industrial areas had the highest LST due to lowest ratio of vegetation to free space area (1%), while ‘green’ areas displayed the lowest LST. Green residential and small-medium public parks had comparable thermal loads, with green residential having slightly lower LST (by 0.5 °C). In general, small-medium public parks displayed higher LST than expected. Inefficient use of free spaces for vegetation, i.e., relatively low vegetation cover to free space ratio, was probably the main cause for this. Public parks had a higher local cooling effect, but a less continuous one on the proximate surrounding (30–90 m from the park), probably due to their relative location in the urban fabric. Our results suggest that ‘greening’ areas within the private urban space should be encouraged at the expense of building new small-medium parks in metropolitan areas that lack the sufficient free space for larger parks. The outcome of this study may have key implications for urban planners seeking to mitigate urban heat island effects under the limitation of existing dense urban layout.     

重庆市主城区物流园区空间布局及其对城市空间结构的影响

选择现代物流业相对发达的西部地区的中心城市—重庆主城区为典型案例,通过对物流园区实地调研与管理部门的访谈获取论证数据展开案例实证。重庆市主城区的物流园区的案例研究发现：① 物流园区的空间布局具有两大特征：一是围绕城市中心区外围布局,二是沿交通干线或重要交通设施布局;② 物流园区的自身建设是城市开发的重要组成部分,其空间布局对城市空间结构的影响一方面促进和引导城市建成区的向外扩张,另一方面体现在物流园区通过自身建设和对周边地区的带动改变城市的用地结构和内部用地功能。最后分析总结了物流园区对城市空间结构影响的4种机制：垄断机制、配套机制、地价机制和聚集机制。     

国内外城市空间结构研究综述

回顾了国内外城市空间结构研究的理论进展,主要评述了不同历史时期研究的主要内容和理论观点.国外研究经历的形态研究、功能研究、人文关怀到空间机制的研究,反映出国外空间结构理论体系的日益完善;相比之下,国内自20世纪90年代中期以来,城市空间结构的研究热点才不断增多,研究内容更加丰富多样.但在学科建设、研究内容和研究方法上,国内外仍然存在较大差距.最后提出了中国城市空间结构研究的发展方向和研究热点.     

中国地级以上城市公园绿地服务水平评估:数据、模型和方法

现有城市公园绿地服务的评估常以给定的城市空间范围和公园绿地为前提,评估对象及其空间范围具有较大随意性,致使很难根据评估结果判断城市公园绿地的空间配置是否合理,或对不同城市进行比较。本文对城市公园绿地服务水平评估的数据、模型和方法进行了梳理,从公园绿地的类别、等级、服务范围和可选择性等要素着眼,提出了以城市建成区内居民至周边公园绿地的可达性为核心的评估指标和模型方法。运用开源空间数据和Densi-Graph分析方法,解决了城市公园绿地空间数据的提取、城市建成区范围的界定、指标构建等关键技术问题,使城市公园绿地的评估获得了客观性、统一性和可比性的保障。对全国273个地级的评估结果表明,我国地级市公园绿地服务覆盖率平均值达到64.8%,尚有超过两成的城市公园绿地服务覆盖率不到50.0%,公园绿地服务水平与现行国家标准之间尚有差距。公园绿地服务水平存在明显的区域差距,服务水平较高的城市显著集中于特大城市、东部沿海发达地区和东北地区,同时,与城市人口规模相对应呈现出S型曲线上升趋势。为避免区域发展的不协调,应增加对中小城市和中西部地区城市绿地公共服务的投入。     

Spatial and Temporal Patterns Associated with Permitted Tree Removal in Austin,Texas, 2002–2011

A wide-ranging set of physical, urban, demographic, socioeconomic, and policy characteristics determines the spatial distribution of urban forests. Information on the characteristics surrounding tree removals on both public and private properties has received less attention in the literature. The purpose of this research was to analyze the spatiotemporal trends and geographic patterns of tree removals in Austin, Texas, between 2002 and 2011 in an effort to understand how site-specific characteristics influence urban tree removal and affect the overall distribution of Austin's urban forest. We examined permitted tree removals using a geographic information system (GIS) as well as spatial and statistical analyses. Specifically, we evaluated the degree to which variables related to various physical, urban, and socioeconomic conditions predicted tree removals. The results indicate that permitted tree removals and their associated characteristics in Austin have varied over the ten-year study period. Permitted tree removals increased over the study period and took place in the urban core and along the urban periphery. Permitted tree removals were more likely to be undertaken by college graduates and owner-occupants and to occur in more densely populated areas, closer to major streets, and on properties with older structures. The results of this research provide urban forest professionals with information on the location and intensity of permitted tree removals and the significant characteristics driving urban tree loss.     

An inventory of trees in Dublin city centre

While urban areas are often considered to be comprised chiefly of artificial surfaces, they can contain a substantial portion of green space and a great diversity of natural habitats. These spaces include public parks, private gardens and street trees, all of which can provide valuable environmental services, such as improved air quality. Trees play a particular role in cities as they are often placed along roadsides and in the median strip of busy streets. As such they regulate access to sunshine, restrict airflow, provide shelter, scavenge air pollutants and manage noise at the street level. A tree planting policy can be an important part of a broader environmental strategy aimed at improving the quality of life in urban areas but this requires up-to-date knowledge of the current tree stock, which does not exist for Dublin. This article presents an inventory of trees in Dublin's city centre, defined as the area between the Grand and Royal canals. The results show that there are over 10,000 trees in the study area representing a density of 684 trees km-2 or one tree to approximately every 50 residents of the city centre. The tree canopy extent when in full foliage was nearly 1 km2 in extent or 6% of the study area. A more detailed analysis of those trees planted along streets shows little species variation but clear distinction in the sizes of trees, which is indicative of the age of planting. These data are used to estimate the carbon stored in Dublin's trees.     

荒漠绿洲过渡带不同立地条件下物种多样性及其与土壤理化因子的关系

通过于2007-2011年对甘肃河西走廊中部荒漠绿洲过渡带不同立地条件下植被样方的调查,应用 Margalef丰富度指数、Pielou均匀度指数、Shannon-Weiner指数和Simpson指数研究了不同立地条件下物种多样性的变化,并采用典范对应分析方法(CCA)研究植物物种分布与土壤环境因子的关系。结果表明：荒漠绿洲过渡带丘间低地的植被盖度和Margalef、Simpson、Shannon-Wiener、Pielou指数值均最大,流动沙丘条件下最小;Hill多样性指数排序结果显示,随着土壤水分条件的变差,物种多样性同样表现出降低的趋势。按多样性从高到低的顺序,其相应的立地条件分别为丘间低地、缓平沙坡、固定沙丘、半固定沙丘和流动沙丘。选取的土壤因子对过渡带植被分布的影响程度大小为土壤含水量＞pH值＞全钾＞有机质＞速效氮＞全氮＞速效钾＞全磷＞土壤盐分＞速效磷。土壤含水量和pH是荒漠绿洲过渡带植被分布空间差异的最主要影响因子,前3个轴的环境解释率为98％,证明排序可信。     

芜湖市城市公园体系等级结构及其时空分布格局

近年来,随着城市化进程的加快,建设城市公园以满足生活需要成了备受关注的热点问题。本文尝试构建城市公园综合吸引力模型,并运用分形、聚类等方法,建立芜湖市城市公园等级体系,并分析其时空分布特征。研究表明：芜湖市城市公园在Z.ipf分布模型中呈现出双分形结构,可分为两个大类六个等级。城市公园体系具有等级层次性不强、高等级公园中心性明显等特征;高等级公园具有极强的老城区指向性、人口稠密区指向性和经济实力强区指向性,低等级公园散布在人口稠密区、数量多、分布范围广;总体上呈现出中心集聚、外围松散,分布不均衡的空间格局。自然条件是公园形成的基础条件,近年来为满足城市发展和城市居民需求,政府规划和企业行为是城市公园形成的决定性因素,各因素相互作用,共同影响着城市公园体系的形成和发展。     

Relationship between landscape heterogeneity and plant species richness on the Mexican Pacific coast

The present study aims to use landscape heterogeneity as a predictor of plant species richness in a tropical dry landscape area in the coast of Michoacán, Mexico. To understand the relationship between species richness and landscape, a three-step approach was followed: first, landscape spatial heterogeneity was measured by classifying landscape types according to their attributes (i.e., environmental, soil and topographic variables). Second, several diversity standard indices were used to explore biological diversity and to select the best one explaining the relationship between landscape heterogeneity and plant species richness, for this study area. Third, from the obtained results it was possible to calculate biodiversity values on the basis of landscape heterogeneity. The results indicate that it is possible to predict more than 61% of species richness through an indicator of landscape heterogeneity (H′; Shannon–Weaver diversity index). This procedure may be useful in terms of land use, conservation, and management of protected areas, mainly in areas with high biodiversity but with limited biological data, since it allows to obtain an approximation of the spatial distribution of species richness, even with scarce biological information.