关键词: 人口密度, 空间演变, 形成机制, 兰州市

Abstract:

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.

Key words: population density, spatial evolution, formation mechanism, Lanzhou City