近30年来兰州市人口密度空间演变及其形成机制

The Spatial Evolution and Formation Mechanism of Population Density in Lanzhou City Over the Past 30 Years

以街区层面的人口统计数据为基础,综合应用ArcGIS和GS+Version7软件对近30 a来兰州市人口密度空间演变进行分析。结果表明:1982-2009年,随着空间距离的增加,人口密度的正相关性逐渐削弱,负相关性逐渐增强。人口密度总体上呈不断增大的趋势,人口分布不均衡性和聚集性逐年增强,整体呈现出东高西低格局,以城关区和西固区为增长顶点形成"双核心"空间结构。高密度人口分布偏东,主要集中在城关区和七里河区。人口重心级别不同,所在街区面积不同,高人口密度街区面积小,低人口密度街区面积大。其形成机制主要缘于自然因素、历史因素、政策因素和经济因素等方面。

Base on the demographic data at a district level,the article analyzed the spatial evolution of population density in Lanzhou in recent 30 years,by a comprehensive application of software ArcGIS and GS＋Version7. The result shows that： 1） in the evolution of spatial pattern in population density of Lanzhou,with the growth of spatial distance,the positive correlation of population density was gradually weakening and the negative correlation was gradually strengthening in 1982-2009.The spatial autocorrelation range has been continuously increased.The influence coverage of the high density area on the low density area has been increasing year by year.The random elements that arouse the spatial difference in population density are increasing continuously, and structure differentiation that space correlation causes is more and more outstanding.The regional difference in population density distribution was enlarging as a whole.It can be predicted that,in the near future, the difference remains and in a short term there will no any great changes.This illustrates that population distribution in Lanzhou is always in an imbalanced state.2） From the changes of population density gravity in different years,it can be seen that,the population distribution is partially on the east.The tendency of space pattern in population distribution shows its regularity,which is high on the east and low on the west as a whole.In two-center space pattern formed by increase peak in Chengguan District and Xigu District,the population density is gradually reducing from center to the surrounding.The general tendency of population density in different years changes little.The high and low population gravities focus on Chengguan District and Qilihe District,which shows the gradual and stable eastward tendency and low population density center is moving at a relatively speed.The moving directions of the gravity of high and medium population density and low population density are opposite,which shows that the difference of population density in districts is enlarging. Meanwhile,as for high population gravity and medium density center,the area of research units of population gravity at the different levels is different.The district area which is high in population density is commonly small,and the district area that is low in population density is generally large.3） The differences in population density of the districts in main urban areas existed in 30 years ago.And the revolution is under combined influences by nature element,history element,policy element and economy element.Among them,nature element is the direct factor that influences population density;history element is the key factor that influences the difference in population density;policy element plays a controlling and leading role in the revolution of space structure in a city;the difference in social and economic development directly influences mechanical growth of population, and makes population gravity transfer.Therefore,economy element is the decisive factor that influences population density distribution.