Transient Responses to Spatial Perturbations in Advective Systems

We study the transient dynamics, following a spatially-extended perturbation of models describing populations residing in advective media such as streams and rivers. Our analyses emphasize metrics that are independent of initial perturbations—resilience, reactivity, and the amplification envelope—and relate them to component spatial wavelengths of the perturbation using spatial Fourier transforms of the state variables. This approach offers a powerful way of understanding the influence of spatial scale on the initial dynamics of a population following a spatially variable environmental perturbation, an important property in determining the ecological implications of transient dynamics in advective systems. We find that asymptotically stable systems may exhibit transient amplification of perturbations (i.e., have positive reactivity) for some spatial wavelengths and not others. Furthermore, the degree and duration of amplification varies strongly with spatial wavelength. For two single-population models, there is a relationship between transient dynamics and the response length that characterizes the steady state response to spatial perturbations: a long response length implies that peak amplification of perturbations is small and occurs fast. This relationship holds less generally in a specialist consumer-resource model, likely due to the model’s tendency for flow-induced instabilities at an alternative characteristic spatial scale.     

The Urban Funnel Model and the Spatially Heterogeneous Ecological Footprint

Urban ecological systems are characterized by complex interactions between the natural environment and humans at multiple scales; for an individual urban ecosystem, the strongest interactions may occur at the local or regional spatial scale. At the regional scale, external ecosystems produce resources that are acquired and transported by humans to urban areas, where they are processed and consumed. The assimilation of diffuse human wastes and pollutants also occurs at the regional scale, with much of this process occurring external to the urban system. We developed the urban funnel model to conceptualize the integration of humans into their ecological context. The model captures this pattern and process of resource appropriation and waste generation by urban ecosystems at various spatial scales. This model is applied to individual cities using a modification of traditional ecological footprint (EF) analysis that is spatially explicit; the incorporation of spatial heterogeneity in calculating the EF greatly improves its accuracy. The method for EF analysis can be further modified to ensure that a certain proportion of potential ecosystem services are left for in situ processes. Combining EF models of human appropriation with ecosystem process models would help us to learn more about the effects of ecosystem service appropriation. By comparing the results for food and water, we were able to identify some of the potentially limiting ecological factors for cities. A comparison of the EFs for the 20 largest US cities showed the importance of urban location and interurban competition for ecosystem services. This study underscores the need to take multiple scales and spatial heterogeneity into consideration to expand our current understanding of human–ecosystem interactions. The urban funnel model and the spatially heterogeneous EF provide an effective means of achieving this goal. Received 17 October 2000; accepted 31 May 2001.     

区域城市扩张对森林景观破碎化的影响——以粤港澳大湾区为例

森林生境丧失与景观破碎化是引起生物多样性下降,生态系统功能降低的重要原因。量化森林景观破碎化的时空特征及其与城市扩张格局的关系是开展区域生态修复与功能提升的重要基础。本文以快速城市化的典型区域——粤港澳大湾区为研究对象,基于遥感解译的1980年、1990年、2000年、2010年和2018年土地覆盖/利用专题图,通过多尺度的景观格局分析和统计分析,定量解析森林景观破碎化的时空演变特征及其与城市扩张格局间的关系。研究结果显示:1)1980—2018年,大湾区林地覆盖面积缩减1,274 km²,林地转变为建设用地的面积占林地丧失总面积的比例从1980—1990年的11%增长至2010—2018年的42%,表明城市扩张已成为林地丧失的主导因素;2)森林景观破碎化程度加剧,表现为林地斑块密度提高,平均斑块面积减小,但破碎类型与程度具有地域差异;3)城市扩张幅度与空间格局显著影响林地破碎化,其中,城市扩张幅度对林地破碎化的影响更为重要。基于森林景观破碎化与城市扩张的现状,落实城市增长边界划定、关键斑块-廊道识别与生态网络构建等措施,有助于保护与连通重要生态空间,保障和提升生...     

雄安新区多尺度生态安全格局构建框架

维持城市所处的生态系统格局与过程,使得城市生存和发展所依赖的关键生态系统服务实现供需平衡是保障城市生态安全的根本要求和基本前提。因此,城市生态安全不仅是城市本身的问题,还涉及到城市所处的流域、区域、国家等多个不同的空间尺度,具体由支撑城市及其发展的关键生态系统服务所涉及的生态过程所决定。对生态安全概念及研究进展进行了梳理和分析,在此基础上,提出了一个城市生态安全保障的生态系统服务研究框架,将维持城市生态安全的关键生态系统服务需求分为3个层次：一是水资源供给、食物生产、水质净化等城市生存所依赖的基础资源与基本环境维持相关的服务,二是土壤保持、水源涵养、防风固沙、固碳释氧、生物多样性等生态系统稳定和可持续性维持相关的生态系统稳定和调节类服务,三是生态休闲、微气候调节、降尘减噪、文化审美等人居环境与文化类服务。进而利用该框架,从不同需求层次分别对雄安新区生态安全保障的生态系统服务需求进行了分析,结合其自然地理特征和新区建设的社会经济发展情景,从新区城市、大清河流域和京津冀区域三个尺度提出了雄安新区生态安全格局构建框架,以及相应的保障对策和建议,包括从多尺度进行生态环境调控和管理,打破行政和地域边界限制;关注各尺度各关键生态系统服务的过程,加强生态环境要素的监测和预警;重视新区在人居环境改善层次的生态系统服务需求等。     

Scaling Theory: Application to Marine Ornithology

The problem of scale has three components: (a) direct measurement is usually confined to small areas and brief periods, (b) the most pressing issues occur at the scale of ecosystems and decades, but (c) direct scale-up fails when pattern and process at small scales differ from those at larger scales. Recognition of this dilemma has grown exponentially since around 1980. The problem of scale is particularly acute for seabirds, which inhabit one of the most extensive habitats on the planet—the surface of the ocean. The application of power laws is a promising solution to the problem. Power laws have a long empirical tradition, are readily estimated from data, and now have a theoretical basis. Power law behavior (with nonintegral exponents) appears in systems with episodically warring exponential rates. In marine ornithology, examples of areas where power laws can be applied include patchy spatial distributions, the association of predator with prey, the scaling of food intake to body size, and fractal habitat structure. Scaling theory and power laws are applicable to a wide variety of ecosystem phenomena and dynamics, including fluxes of material and energy. Received 7 May 2001; accepted 12 April 2002.     

从“增量扩张”到“存量优化”:深圳市景观格局内部动态与优化

随着城市化的不断推进,以城市扩张为主要特征的土地城市化渐趋于饱和,许多城市开始进入"存量优化"的土地开发阶段。存量优化的土地开发模式改变了城市内部的景观格局,进而影响城市景观的生态过程及功能,但现有的工作主要关注城市的外部扩张,缺乏对城市内部景观动态的研究。以深圳市为例,基于高空间分辨率遥感影像,以地块为分析单元,识别城市扩张、城市更新以及内部填充三种土地开发方式,对比分析不同方式下地块的景观格局变化。研究结果表明：（1）深圳市已进入"存量优化"的城市发展阶段,表现为内部存量变化面积是外部增量变化的2倍;（2）城市更新类型的地块平均植被比例增加3%,提高了人居环境质量,而城市扩张和内部填充类型的地块则表现为植被比例明显下降,平均植被比例分别减少了51%和50%;（3）城市扩张和城市更新具有明显的空间聚集特征,内部填充分布则相对随机。在精细空间尺度上识别了城市扩张、城市更新以及内部填充三种不同景观变化类型,分析了其空间分布特征,为深入理解城市内部景观格局的动态变化提供了新的视角,可为城市生态过程的机理研究和城市规划提供参考与借鉴。     

Persistence of subtle departures from symmetry over multiple molts in individual brachyuran crabs: Relevance to developmental stability

Fluctuating asymmetry (FA) is generally viewed as a population-level character. It is described by some measure of the variance of the difference between the right and left sides for a collection of individuals. Very little is known of the developmental origins of FA, despite the fact that FA is widely used to estimatedevelopmental stability. We present a novel technique for examining the growth trajectory of the asymmetries that give rise to FA, and we explore two sample data sets for the brachyuran crabHemigrapsus nudus. We have traced the fate of these small, random deviations from perfect symmetry through three successive molts of individual crabs. Invertebrates that molt, and hence grow in discrete steps, provide an easily preserved record of their growth. Model II regressions of measurements from one molt versus the previous molt can help describe the stability of subtle departures from symmetry over time. Although any number of different patterns may occur, we identify four general cases: a) asymmetries vary at random throughout growth (random determination), b) asymmetries remain unchanged in sign and magnitude (constant asymmetries), c) asymmetries increase in proportion to character size and hence increase with growth (size-dependent asymmetries), and d) asymmetries persist, but are reduced in magnitude (damped asymmetries). Data from tenHemigrapsus nudus, measured for between 21 and 28 metrical, limb-segment characters over three successive molts, yielded associations most similar to our pattern ‘b’, although some subtle departures in the direction of pattern ‘c’ were also observed. Persistent asymmetries accounted for 26% and 20% of the variance among asymmetries between molts 1 and 2, and molts 2 and 3 respectively. Thus, in spite of large and rapid increments in the external size of the crab, these subtle asymmetries tended to persist in both direction and magnitude, from molt to molt. This result suggests either i) that individual crabs have a genetic predisposition towards asymmetry in a particular direction but contribute to a continuous and normal distribution ofR-L differences at the population level, or ii) that these subtle asymmetries arose at some earlier ontogenetic stage and were preserved through growth. Either interpretation has important ramifications for the study of FA. The first suggests that under some circumstances FA may not provide a valid measure of developmental instability, because subtle departures from symmetry in an individual may have a genetic basis. The second implies that subtle departures from bilateral symmetry are not ‘corrected’ as an individual grows.     

基于无人机航测的漯河市土地利用景观格局尺度效应

景观格局的尺度效应一直是景观生态学研究的核心内容,对于揭示景观空间格局变化规律及其生态过程具有重要意义。以漯河市中心城区为研究对象,基于景观生态学原理,采用无人机航测技术获取空间分辨率为0.09 m的无人机影像,结合GIS空间分析法,量化分析了漯河市土地利用景观格局的尺度效应。结果表明:(1)漯河市中心城区土地利用景观格局具有明显的粒度和幅度效应。(2)粒度越小,景观格局指数随空间粒度的变化趋势越稳定,其表达的生态过程越真实;景观水平上景观格局的粒度效应是由建筑、道路和绿地景观在景观优势度、破碎度和聚集度等方面的变化导致的;35 m和3 m分别为研究粒度效应的临界阈值和最佳粒度。(3)景观优势度、破碎度和蔓延度随空间幅度的增加而降低,景观复杂程度和聚集度随空间幅度的增加而增加;景观格局具有明显的空间梯度分布特征——从市中心往外由不透水地面向透水地面过渡;建筑和道路在城市中心区聚集度较高,而绿地景观在城市内部破碎度较高,进而主导了整体景观格局的梯度变化;景观组分的稳定与城市规模有关。(4)无人机航测技术可以更快速、准确地获取城市尺度上的景观生态信息,揭示景观格局对尺度效应的响应特征,可为景观格局优化和城乡景观规划提供科学依据。     

多尺度生态系统服务的权衡关系及其对景观配置的响应——以湖北省为例

多种生态系统服务相互关系及其对景观配置响应的多尺度分析一直是生态系统服务研究的热点问题,对于厘清生态系统服务尺度效应和实现区域分级管理具有重要的意义。以湖北省为研究区域,采用遥感、土地利用类型、水文、气象、土壤等多元数据,从5 km×5 km、10 km×10 km、15 km×15 km、20 km×20 km、25 km×25 km、县域和市域等7个递增尺度分析4种生态系统服务(水源供给、碳固持、粮食生产、水质净化)对景观配置的响应关系。结果表明：(1)4种生态系统服务的空间分布具有较强的异质性,粮食生产服务的高值区与水质净化服务的低值区主要分布于湖北省中部和东部的耕地集中区域,碳固持与水源供给呈现相反的空间特征。(2)生态系统服务权衡关系的作用强度随尺度增加而减弱,而协同关系呈增加趋势;同时服务间相互作用强度的变化大于作用方向的变化。(3)景观配置对生态系统服务的影响程度在县域和市域尺度上大于格网尺度。结果反映了受尺度变化中“削峰填谷”过程的影响,景观配置对生态系统服务影响的大小和正负效应具有尺度差异性。研究结果可为区域生态系统服务分级管理和景观格局调控提供科学参考。     

南京市景观时空动态变化及其驱动力

选择南京市1995、2000和2008年的土地利用/土地覆盖数据,对其土地利用斑块动态变化与景观斑块的空间稳定性进行探讨。结果表明,全市总体上以耕地、林地和草地的减少,以及建设用地和水域的大幅度增加为典型特征。1995-2000年间耕地、林地和草地面积净减少了12017.2 hm²,2000-2008年间净减少41029.13 hm²;全市的建设用地面积1995-2000年间仅增加了11981.3 hm², 2000-2008年间面积增加了41027.06 hm²。从斑块类型的面积稳定性来看,各种土地利用斑块的空间稳定性都非常高,除了2000-2008年间未利用土地的自身空间保持率为50.66%外,其他土地景观类型的保持率都在90%以上。从不稳定斑块的空间分布看,1995-2000年间,主要集中在南京市的栖霞区、浦口区和江宁区,呈离散分布特征; 2000-2008年间,不稳定斑块一方面呈现出集中连片的分布态势,这在江宁区和栖霞区最为典型,另一方面这种集中分布趋势也扩大到了六合区与高淳县。从不稳定斑块的转化方向看,均以建设用地所占比例最大,两个时段内转为建设用地的不稳定斑块分别占到了不稳定斑块总面积的87.09%和68.46%,其次的转化方向为水域,两个时间段内分别达到了10.61%和23.86%。从景观斑块变化的原因来看,对当地景观斑块稳定性影响最大的主要是人口与经济发展、城市规划的引导和重大的生态建设工程等人为因素。     

Taylor's law and related allometric power laws in New Zealand mountain beech forests: the roles of space,time and environment

Taylor's law says that the variance of population density of a species is proportional to a power of mean population density. Density–mass allometry says that mean population density is proportional to a power of mean biomass per individual. These power laws predict a third, variance–mass allometry: the variance of population density of a species is proportional to a power of mean biomass per individual. We tested these laws using 10 censuses of New Zealand mountain beech trees in 250 plots over 30 years at spatial scales from 5 m to kilometers. We found that: 1) a single‐species forest not disrupted by humans obeyed all three laws; 2) random sampling explained the parameters of Taylor's law at a large spatial scale in 8 of 10 censuses, but not at a fine spatial scale; 3) larger spatial scale increased the exponent of Taylor's law and decreased the exponent of variance–mass allometry (this is the first empirical demonstration that the latter exponent depends on spatial scale), but affected the exponent of density–mass allometry slightly; 4) despite varying natural disturbance, the three laws varied relatively little over the 30 years; 5) self‐thinning and recruiting plots had significantly different intercepts and slopes of density–mass allometry and variance–mass allometry, but the parameters of Taylor's law were not usually significantly affected; and 6) higher soil calcium was associated with higher variance of population density in all censuses but not with a difference in the exponent of Taylor's law, while elevation above sea level and soil carbon‐to‐nitrogen ratios had little effect on the parameters of Taylor's law. In general, the three laws were remarkably robust. When their parameters were influenced by spatial scale and environmental factors, the parameters could not be species‐specific indicators. We suggest biological mechanisms that may explain some of these findings.     

福寿螺表型性状的空间尺度变异

格局和尺度是生态学的核心概念。尺度的变化可能导致生态学格局的改变。入侵物种性状的变异会对种群的建立和扩散产生重要的影响。为了研究入侵物种福寿螺(Pomacea canaliculata)表型性状的尺度变异并推测可能的作用机制,在广东省开展了福寿螺的体质量、体高、体宽、壳口宽4个表型性状在城市、乡镇、生境、样方、个体5个空间尺度上变异的研究。通过拟合混合模型,进行方差分解,结果发现个体和样方差异解释了近80%的性状变异,生境的差异解释了除体重外其他性状的剩余变异;除体重外乡镇和城市尺度上性状的变异并不明显。结果进一步表明,区域尺度的过程如气候特征等对福寿螺表型性状变异不起主要作用;福寿螺种群特征的研究及防控的重点应考虑其遗传结构特征及局部尺度环境因素。通过不同尺度下性状的变异系数和频度分布曲线的分析,进一步验证了以上结果。     

城市空间形态紧凑度模型构建方法研究

我国城市空间形态的急剧变化给经济、社会、城市建设等带来诸多问题,使相对脆弱的城市生态环境承受巨大的压力,对城市可持续发展构成了一定的影响。深入了解城市景观的格局演变过程和机理,并构建适宜的城市空间形态定量化评价模型对于推进我国城市可持续发展、合理利用和保护区域生态环境具有重要的现实意义,也是我国城市发展的紧迫需求。在Thinh等提出的城市紧凑度算法的基础上,构建了一种城市空间形态定量化评价指标,即标准化紧凑度指数(normalized compactness index, NCI)。NCI将圆形区域作为标准度量单位,实现测算结果的标准化,在一定程度上避免了城市面积因素对评价结果所带来的影响,因而便于城市之间或同一城市不同时段间的城市空间形态紧凑程度的比较分析,为城市空间形态紧凑程度的定量评价提供了一种新的技术方法。     

Nanoscale nucleosome dynamics assessed with time-lapse AFM

A fundamental challenge associated with chromosomal gene regulation is accessibility of DNA within nucleosomes. Recent studies performed by various techniques, including single-molecule approaches, led to the realization that nucleosomes are dynamic structures rather than static systems, as was once believed. Direct data are required in order to understand the dynamics of nucleosomes more clearly and to answer fundamental questions, including: What is the range of nucleosome dynamics? Does a non-ATP-dependent unwrapping process of nucleosomes exist? What are the factors facilitating the large-scale opening and unwrapping of nucleosomes? This review summarizes the results of nucleosome dynamics obtained with time-lapse AFM, including a high-speed version (HS-AFM) capable of visualizing molecular dynamics on the millisecond time scale. With HS-AFM, the dynamics of nucleosomes at a sub-second time scale was observed, allowing one to visualize various pathways of nucleosome dynamics, such as sliding and unwrapping, including complete dissociation. Overall, these findings reveal new insights into the dynamics of nucleosomes and the novel mechanisms controlling spontaneous chromatin dynamics.     

城市空间形态离散度指数NDIS构建与应用

中国土地资源有限,需要可持续的、紧凑的城市空间形态与布局,因此,全面度量城市空间形态的紧凑性具有重要意义。通过6个情境分析了离散度指数DIS的优缺点,识别出DIS值在反映城市形态紧凑程度方面的不足,进而提出了一种新的城市空间形态紧凑度指数,即标准化离散度指数NDIS。NDIS不受城市面积规模的影响,且具有唯一性,利于城市紧凑度的横向和纵向比较,能更好地指示城市空间形态。NDIS值越大,城市越离散。进一步将NDIS与成熟使用的标准化紧凑度指数NCI结合,用于分析中国35座城市的空间形态紧凑性,研究结果表明:(1) NDIS最大值是兰州市的1.64,最小值是石家庄市的1.14,均值1.29±0.12(SE); NCI最大值是郑州市0.39,最小值是宁波市的0.1,均值0.24±0.07(SE);(2) NDIS与NCI虽然具有中等程度的相关性(r=-0.44,P0.01),但是NDIS把城市斑块间的距离关系表达得更为准确;(3)将NDIS与NCI结合,能够更加全面地指示城市空间形态的紧凑程度。准确、全面的衡量中国城市的空间形态,则需要与更多的景观格局指数结合使用。     

承载力评估在区域人口配置中的应用:以常州为例

从城市生态系统承载力的空间差异性出发,集成GIS空间评价技术和系统动力学(SD)模型,确定城市区域适度总人口规模和各分区人口数量,提出人口分区定量配置新思路和技术集成方法,并将该方法应用于300万人口城市——常州.结果表明:通过构建常州市区人口、经济、土地与环境的系统动力学模型和多情景模拟分析,在同时满足城市经济发展与环境保护需求下,常州市区远景(2050年)总人口约400万;基于城市承载力空间差异评价进行常州市区总人口的空间配置,将形成240万人的主城及5个15 ～ 40万人新城的空间格局,研究结果可为国土开发管理中人口与经济的空间分配提供科学依据.     

城市社区尺度花粉致敏风险评估方法研究进展

目前,花粉过敏性疾病在国内外城市中均具有较高发病率。作为城市居民生活的基本单元,社区对居民健康有重要的影响。因此,社区尺度的花粉致敏风险评估研究是提升居民健康的重要抓手。鉴于此,研究从花粉产生的植物本体角度和影响花粉传播的空间环境角度系统地综述了影响社区花粉致敏风险的相关因素,并进一步梳理了花粉致敏风险的评估方法。研究发现:在空间尺度上,目前国内外评估花粉致敏风险相关方法主要应用于微观的植物尺度与宏观的城市尺度,在中观尺度的应用仅局限于校园、公园中的绿地,尚未对社区进行研究;在评估因素上,现有评估方法多关注植物自身因素,如树木高度、冠幅等因素,而较少涉及诸如通风、温湿度等环境因素;然而社区中环境条件复杂,建筑环境不容忽视,因此了解植物与环境的综合作用对于社区花粉致敏风险的评估至关重要。基于上述发现,提出未来建立适宜社区尺度的致敏评估方法的可能途径:首先应建立适用于评估社区常用植物的统一标准数据集,在综合考虑植物因子、社区环境因子和临床患病率等各类因子的基础上建立社区花粉致敏风险评估方法,还可利用可视化技术建立包含社区三维特征的模型来模拟社区花粉分布及扩散规律,确立社区尺度下花粉致敏风险评估方法,降低社区花粉致病率,进一步提升居民健康水平。     

国土空间规划视角下健康城市规划评价指标体系构建

随着“健康中国”战略的持续推进,通过干预空间要素提升国民健康的城市规划受到了广泛的关注。在国土空间规划视角下建立了城市空间要素与健康关联性理论框架,从土地利用、交通环境、空间形态、蓝绿空间、食品环境、空间感知与突发公共卫生事件空间应对7个维度,提出了媒介性空间要素对居民生理、心理健康的五大影响路径,包括减少污染源和人体暴露风险、促进体力活动、促进健康饮食、促进社会交往以及提供可获得的健康设施。据此构建了“多要素、多维度、多尺度”健康城市规划评价指标体系,包含基础、新增和潜在指标。其中,“多要素”强调引入七大类空间要素构建全面而多样化的指标体系,“多维度”强调从传统的城市平面维度向立体空间转变,包含一维、二维和三维空间层面的评价指标,“多尺度”指构建“城市-社区-人”框架下的多尺度指标体系。结合各地实际,可从重视人本尺度、强化空间属性、引入突发公共卫生事件的空间应对以及三维指标的精准量化出发,制定有针对性的规划干预策略,并推动健康城市项目的发展完善,为“健康中国”战略在城市层面的推进提供参考。     

Local contagion and regional compression: habitat selection drives spatially explicit,multiscale dynamics of colonisation in experimental metacommunities

Habitat selection, including oviposition site choice, is an important driver of community assembly in freshwater systems. Factors determining patch quality are assessed by many colonising organisms and affect colonisation rates, spatial distribution and community structure. For many species, the presence/absence of predators is the most important factor affecting female oviposition decisions. However, individual habitat patches exist in complex landscapes linked by processes of dispersal and colonisation, and spatial distribution of factors such as predators has potential effects beyond individual patches. Perceived patch quality and resulting colonisation rates depend both on risk conditions within a given patch and on spatial context. Here we experimentally confirm the role of one context‐dependent processes, spatial contagion, functioning at the local scale, and provide the first example of another context‐dependent process, habitat compression, functioning at the regional scale. Both processes affect colonisation rates and patterns of spatial distribution in naturally colonised experimental metacommunities.     

城市绿色空间可达性与居民分布的空间匹配与影响因素

城市居民的绿色空间可达性是衡量城市基础设施公平分配的指向标,关乎城市民生福祉。以宁波为研究区,基于高德地图路径规划Application Programming Interface(API)测度了绿色空间可达性,融合多源数据模拟了人口空间分布,分析了绿色空间可达性与人口分布的空间匹配状态,并采用地理探测器探讨其影响因素。研究表明：(1)宁波绿色空间可达性由各区中心向郊区衰减,高可达性空间占比不高,反映了绿色服务供给不足的现状。高可达性空间集中于三江口、鄞州新城、北仑城区和镇海老城区,低可达性空间则主要分布在东部郊区、西部山区和南部农业区。(2)宁波居民的绿色空间可达性在空间上表现为市中心高人口密度-高可达性和郊区低人口密度-低可达性的空间匹配特征,在规模上仅不及半数的居民享有15min绿色空间可达性,在乡镇尺度上呈现显著的城区—郊区二元类型分异。(3)城市居民绿色空间可达性受多重影响因子驱动,按照重要性依次为区位特征、人类活动、开发强度、社会经济和地形条件。