1843—2020年上海城市扩张时空过程及机理分析

Spatio-temporal process and mechanism analysis of Shanghai's urban expansion in 1843-2020

上海作为中国近现代城市化最为显著的城市之一,自1843年开埠以来城市格局与空间范围变化巨大,重建并分析其扩张过程,对于深刻理解上海乃至中国城市化进程具有重要意义。本文通过收集1843—2020年上海城市旧地图、中华民国(1912—1949年)地形图、解密卫星影像、遥感数据等多源多精度城市空间数据,分别提取城市建成区信息,重建了开埠以来建成区时间序列,研究了上海开埠以来的城市扩张时空过程及机理。结果表明:(1) 1843—2020年上海建成区面积增长了约1453倍,扩张速率、扩张强度发生了剧烈变化;(2)紧凑度随着时间推进不断下降,分形维数则随着时间变化呈现出了一定的周期;(3)建成区重心位置呈现出先向北后向南发展的趋势,其中最主要的扩张方向为西南及南偏西;(4)优越的自然位置奠定了上海被选为开埠城市发展的先决条件,社会变迁及政策驱动作为最根本的驱动力决定着城市在不同阶段发展的最主要方向,产业经济发展、人口迁移、交通发展等多因素也在复合影响着这一时空过程。本文廓清了上海自开埠以来的城市扩张过程及机理,为更深刻理解城市变迁、人地关系演变提供历史知识与科学支撑;同时,中华民国地形图、解密影像等覆盖范围广、制作精度高的历史资料,可作为百年尺度研究的历史基础数据,对更长时序研究具有重要的启发意义。

Shanghai is one of the most significantly urbanized cities in modern China,and its urban spatial pattern and urban area have changed dramatically since its opening up(1843-2020).Reconstructing and analyzing the expansion process of Shanghai has great importance toward attaining a deeper understanding of China's urbanization.This study collected multisource and multi-precision urban spatial data such as old urban maps,topographic maps of the Republic of China(1912-1949),declassified images from the U.S.military(KeyHole),and remote sensing data(Landsat),and reconstructed a long time series of urban built-up areas,and finally examined the evolution process and driving forces of the spatial structure of Shanghai.The results show that:(1)Since 1843,the area of urban built-up areas increased tremendously,with a total expansion of about 1453 times,and the expansion rate and expansion intensity also changed drastically.(2)The overall change trend of compactness is decreasing,and the fractal dimension shows a certain cycle.(3)The center of gravity of the built-up area in different periods showed a trend of developing first to the north and then to the south,and the most important direction of expansion was southwest and west by south.(4)The urban change was complicated by multiple driving factors:the natural location established the prerequisite for the development of Shanghai as a port city;as the most fundamental driving force,social change and policy determined the main direction of urban development at different stages;the spatial agglomeration of industry and trade is the direct cause of the formation and expansion of cities;population migration also injected new impetus into the urbanization;transportation,as an urban infrastructure,has been used to strengthen the connection between the city's external and internal regions.This study clarifies the processes and mechanisms of urban expansion in Shanghai and provides historical knowledge and scientific support for a deeper understanding of urban change and the evolution of the human-land relationship.Moreover,the ways in which a set of general data with a wide coverage and high resolution can be used for the study of the spatial and temporal processes of urban expansion on a centennial scale are discussed,which is quite instructive for understanding the pre-remote sensing era and developing longer time series.