Landscape metrics for three-dimensional urban building pattern recognition

Understanding how landscape pattern determines population or ecosystem dynamics is crucial for managing our landscapes. Urban areas are becoming increasingly dominant social-ecological systems, so it is important to understand patterns of urbanization. Most studies of urban landscape pattern examine land-use maps in two dimensions because the acquisition of 3-dimensional information is difficult. We used Brista software based on Quickbird images and aerial photos to interpret the height of buildings, thus incorporating a 3-dimensional approach. We estimated the feasibility and accuracy of this approach. A total of 164,345 buildings in the Liaoning central urban agglomeration of China, which included seven cities, were measured. Twelve landscape metrics were proposed or chosen to describe the urban landscape patterns in 2- and 3-dimensional scales. The ecological and social meaning of landscape metrics were analyzed with multiple correlation analysis. The results showed that classification accuracy compared with field surveys was 87.6%, which means this method for interpreting building height was acceptable. The metrics effectively reflected the urban architecture in relation to number of buildings, area, height, 3-D shape and diversity aspects. We were able to describe the urban characteristics of each city with these metrics. The metrics also captured ecological and social meanings. The proposed landscape metrics provided a new method for urban landscape analysis in three dimensions.     

福建省旅游小镇空间分布特征及影响因素研究

以福建省155个旅游小镇为研究样本,运用空间统计分析法对其空间分布特征及影响因素进行研究。结果表明：① 福建省旅游小镇空间分布整体上趋于均匀状态,在各个地市的数量分布上也相对均衡;② 福建省旅游小镇核密度呈现出“东高、西低”的分布特征,生态人居型旅游小镇分布密度最大,特色产业型旅游小镇分布密度最小;③ 福建省旅游小镇发展以冷点区和次冷点区为主,冷点区和热点区空间差异明显;④ 经济基础、城镇化水平、人口密度、客源市场是福建省旅游小镇空间分布的主要影响因素。     

超短期风速预报方法研究进展

综合分析国内外风速预报相关文献,从物理方法、统计与机器学习方法、组合方法3个方面对超短期风速预报方法的研究现状进行归纳总结,对比了主要预报方法的优缺点,给出了不确定分析和误差评价指标,探讨了在超短期风速预报研究中应重点解决的问题和发展方向。     

Examining the distribution and dynamics of impervious surface in different function zones in Beijing

Impervious surface (IS) is often recognized as the indicator of urban environmental changes. Numerous research efforts have been devoted to studying its spatio-temporal dynamics and ecological effects, especially for the IS in Beijing metropolitan region. However, most previous studies primarily considered the Beijing metropolitan region as a whole without considering the differences and heterogeneity among the function zones. In this study, the subpixel impervious surface results in Beijing within a time series (1991, 2001, 2005, 2011 and 2015) were extracted by means of the classification and regression tree (CART) model combined with change detection models. Then based on the method of standard deviation ellipse, Lorenz curve, contribution index (CI) and landscape metrics, the spatio-temporal dynamics and variations of IS (1991, 2001, 2011 and 2015) in different function zones and districts were analyzed. It is found that the total area of impervious surface in Beijing increased dramatically during the study period, increasing about 144.18%. The deflection angle of major axis of standard deviation ellipse decreased from 47.15° to 38.82°, indicating the major development axis in Beijing gradually moved from northeast-southwest to north-south. Moreover, the heterogeneity of impervious surface’s distribution among 16 districts weakened gradually, but the CI values and landscape metrics in four function zones differed greatly. The urban function extended zone (UFEZ), the main source of the growth of IS in Beijing, had the highest CI values. Its lowest CI value was 1.79 that is still much higher than the highest CI value in other function zones. The core function zone (CFZ), the traditional aggregation zone of impervious surface, had the highest contagion index (CONTAG) values, but it contributed less than UFEZ due to its small area. The CI value of the new urban developed zone (NUDZ) increased rapidly, and it increased from negative to positive and multiplied, becoming an important contributor to the rise of urban impervious surface. However, the ecological conservation zone (ECZ) had a constant negative contribution all the time, and its CI value decreased gradually. Moreover, the landscape metrics and centroids of impervious surface in different density classes differed greatly. The high-density impervious surface had a more compact configuration and a greater impact on the eco-environment.     

中国城际技术转移网络的空间格局及影响因素

基于2015年专利交易数据,融合数据挖掘、社会网络、空间分析等方法,从节点、关联、模块及影响因素4个方面揭示中国城际技术转移的空间格局及其影响因素：① 技术转移整体强度偏低,空间极化严重,长三角、珠三角、京津冀城市群成为技术转移的活跃地带。② 北京、深圳、上海、广州是全国技术转移网络的“集线器”,发挥城际技术流的集散枢纽和中转桥梁作用,中西部大部分城市处于网络边缘,整个网络发育典型的核心—边缘式和枢纽—网络式结构。③ 技术关联的空间层级和马太效应凸显,形成以北京、上海、广深为顶点的“三角形”技术关联骨架结构,技术流集聚在东部地带经济发达的城市之间和具有高技术能级的城市之间,中西部技术结网不足,呈现碎片化。④ 技术转移网络形成明显的四类板块（子群）,具明显自反性和溢出效应,其空间聚类既有“近水楼台先得月”式块状集聚,也有“舍近求远”式点状“飞地”镶嵌。⑤ 城际技术流呈现等级扩散、接触扩散、跳跃扩散等多种空间扩散模式,其流向表现出经济指向性和行政等级指向性特征。⑥ 城市经济发展水平、对外开放程度、政策支持等主体属性和地理、技术、社会、产业邻近性的城市主体关系均会影响其技术转移强度。     

“一带一路”沿线国家贸易网络空间结构与邻近性

“一带一路”倡议致力于构建全方位、多层次、复合型的互联互通网络,沿线国家之间相互贸易形成的网络有利于加速经济要素跨区域的自由流动,进一步提升“一带一路”区域经济资源的整合效率,对重塑欧亚大陆政经版图和优化中国地缘环境具有重大影响。采用复杂网络和地统计方法,借助GIS、Pajek、Ucinet和数据库等技术手段,对“一带一路”贸易网络的拓扑性质、空间结构以及节点的邻近性深入研究。主要结论有：① “一带一路”沿线国家贸易网络具有小世界和无标度性质,遵循增长性和择优选择;② 沿线国家贸易具有典型的“核心—边缘”等级性,中国对沿线国家产业升级和经济发展具有引领和带动作用;③ 贸易网络是“混合型”结构,呈现枢纽辐射式为主、全连通式并存的联系模式,不同中心性空间分布差异显著;④ 拓展引力模型对“一带一路”沿线国家贸易网络具有较强的解释力,贸易关系存在大国效应和地理邻近效应,科研邻近和语言邻近是重要的推动力,制度邻近的影响呈显著负相关,文化邻近的正向作用相对较弱。因此,中国宜遵循“由近及远”的原则,重点强化对邻近国家的贸易渗透,再加强对沿线重点国家的贸易辐射,进而向重点国家的周边地区拓展,从不同空间层次制定差异化政策,发挥科研和语言邻近的推动作用,强化对沿线国家的文化渗透。     

Investigation of terrain illumination effects on vegetation indices and VI-derived phenological metrics in subtropical deciduous forests

We used RapidEye and Moderate Resolution Imaging Spectroradiometer (MODIS)/Terra data to study terrain illumination effects on 3 vegetation indices (VIs) and 11 phenological metrics over seasonal deciduous forests in southern Brazil. We applied TIMESAT for the analysis of the Enhanced Vegetation Index (EVI) and the Normalized Difference Vegetation Index (NDVI) derived from the MOD13Q1 product to calculate phenological metrics. We related the VIs with the cosine of the incidence angle i (Cos i) and inspected percentage changes in VIs before and after topographic C-correction. The results showed that the EVI was more sensitive to seasonal changes in canopy biophysical attributes than the NDVI and Red-Edge NDVI, as indicated by analysis of non-topographically corrected RapidEye images from the summer and winter. On the other hand, the EVI was more sensitive to terrain illumination, presenting higher correlation coefficients with Cos i that decreased with reduction in the canopy background L factor. After C-correction, the RapidEye Red-Edge NDVI, NDVI, and EVI decreased 2%, 1%, and 13% over sunlit surfaces and increased up to 5%, 14%, and 89% over shaded surfaces, respectively. The EVI-related phenological metrics were also much more affected by topographic effects than the NDVI-derived metrics. From the set of 11 metrics, the 2 that described the period of lower photosynthetic activity and seasonal VI amplitude presented the largest correlation coefficients with Cos i. The results showed that terrain illumination is a factor of spectral variability in the seasonal analysis of phenological metrics, especially for VIs that are not spectrally normalized.     

黑河流域中游张掖绿洲景观格局研究

在解译的张掖绿洲土地利用/土地覆盖图的基础上, 进行相关的景观类型综合处理, 计算了绿洲景观格局的多个指数. 结果表明, 绿洲景观的组成以戈壁、沙地、耕地和草地为主, 体现了荒漠基质受人工影响而形成的典型农业型绿洲的特点. 绿洲内居民点众多, 仅与少数类型邻接并且比较分散, 戈壁、平原旱地和沙地分布则比较集中. 盐碱地和裸岩石砾地的形状最复杂, 戈壁的形状则最简单; 同时, 平原旱地、戈壁和裸岩石砾地的连接性均较好, 在景观中占有较大比重, 类型间的物质和能量迁移比较通畅.     

长三角城市科研合作的邻近性与自组织性

随着学者们对知识网络研究的深入,网络关联的影响因素和作用机制成为重要议题。本文基于2019—2020年Web of Science论文合作发表数据构建长三角城市科研合作网络,在空间和拓扑特征分析的基础上,采用加权指数随机图模型定量模拟了城市属性、城际关系和网络结构对合作网络的影响,揭示了科研合作中的邻近性和自组织性。研究发现：① 长三角城市科研合作网络是内外生动力共同作用的结果。就城市禀赋而言,高校数量、研发投入、人均GDP可促进城市的对外科研合作,其中高校数量的边际效应最大。② 就城际关系而言,组织邻近性的正向影响最强,同省城市合作的概率是跨省城市的3.157倍;认知邻近性每提高0.1,城市间的合作概率将是原先的1.981倍;而地理和社会邻近性的促进作用甚微,制度和文化邻近性影响为负,是择优偏好较强和方言壁垒有限的结果。③ 就网络结构而言,长三角城市科研合作具有自组织自演化性,局部星型结构和三角形结构对新合作关系的贡献为0.875和0.540,择优链接性强于传递闭合性。     

不同邻近性视角下城市网络外部性、集聚外部性对城市经济的影响——以辽宁省城市网络为例

不必地理邻接即可产生外部性关系,城市网络外部性对传统基于地理距离的集聚外部性理论形成挑战,也诱发多种外部性对城市经济发展影响的新思考。因此本文以辽宁省城市网络为研究案例,通过城市间地理距离、手机通话数据与手机信令数据构建距离权重矩阵来表征不同的邻近性,并基于外部性理论、空间计量模型与社会网络分析方法,来探究不同邻近性视角下城市网络外部性、集聚外部性对经济溢出的各自影响和共同作用。研究发现：① 不同邻近性视角下两种外部性的共同作用,比二者之一对城市经济溢出影响更加显著;② 不同邻近性视角下两种外部性影响方向有所不同,地理与信息邻近性视角下两种外部性的共同作用抑制城市经济外溢,社会邻近视角下则促进城市经济外溢,地理邻近性仍然占据主要地位;③ 由于城市规模与控制能力差异较大,辽宁省城市网络难以实现正向的经济外溢,但社会邻近下的人口流动能够促进溢出。因此,处于大城市周边的中小城市需积极参与和主动嵌入城市网络中,才有可能获得转变“外部不经济”为正向溢出的机会,应重视城市之间人口流动与社会联系对区域发展平衡的作用。