Study On Urban Land Expansion And Its Ecological Environment Effect

With the rapid development of China’s urbanization,the level of urbanization is also rising.Cities have increasingly become the center of regional economy,politics and culture in China.Due to the rapid growth of urban population,industrial agglomeration and intensification of human social and economic activities,there is a great demand for urban land space,which makes China one of the countries with the fastest urban land expansion rate in the world.The large expansion of urban land,the continuous occupation of surrounding land,the change of land spatial structure,and unreasonable development and utilization will damage the surrounding environment,resulting in the changes of plant and animal population morphology and regional atmospheric chemical properties,and lead to a series of ecological and environmental problems,such as:a large number of vegetation reduction,temperature rise,water resources depletion,air Pollution and the decline of urban self-regulation function have destroyed the original urban ecosystem,and gradually become the key factors affecting and hindering China’s economic growth,social stability,people’s physical and mental health,and sustainable land development.First of all,in order to understand the relationship between urban expansion,urban expansion speed and urban land use intensity,this paper studies the relationship between urban expansion,urban expansion speed and urban land use intensity Secondly,the NDVI vegetation data layer is extracted from MODIS data to analyze the change of urban vegetation coverage and spatial distribution with time,and then the land surface temperature is reflected by remote sensing thermal infrared image,and the thermal field variation index is obtained The quantitative analysis of heat island effect is carried out to clarify the changes of vegetation and heat island effect in the process of urban land expansion in Dalian.Finally,based on the ecological concept,countermeasures and suggestions are put forward for urban land expansion and ecological environment construction in Dalian.The research on the urban land expansion and its eco-environmental effects in Dalian can provide decision-making basis for the rational planning and management of urban land resources,provide reference opinions for the rational allocation of various types of land,provide theoretical support for strengthening the management of urban ecosystem and formulating a more reasonable protection mechanism of ecological environment system,and expand the problem of urbanization We should pay attention to the harm to the ecological environment in the process of urbanization.The main conclusions of this paper are as follows:(1)In the research time interval,the intensity and speed of urban construction land area growth in Dalian have experienced a rapid first,then a slow and rapid process;the urban land expansion direction is mainly along the southwest and Northeast;Dalian urban land expansion mode type is mainly marginal expansion type,with enclave type expansion type as the auxiliary,and a small amount of filling type expansion type Based on the analysis of the change of construction land,the dynamic change process of urban spatial expansion mode is:from single center circle filling type to multi node leaping edge expansion type to double city compound expansion type to three-level urban structural expansion type at present;know economy and population,urbanization development,public transportation and road and Bridge development,natural environment factors,politics Government policies and planning have different effects on urban land expansion.(2)In the study area of Dalian City,from 2008 to 2018,a large number of construction land replacing vegetation plots appeared in the city,the vegetation area decreased and the vegetation became sparse obviously,the vegetation boundary also gradually reduced along the southwest and northeast directions,the overall trend of vegetation in the study area tended to decline,the vegetation coverage level also showed a downward trend,and the density and growth of vegetation were different The decline and decline of the degree mainly showed that the coverage of very dense vegetation changed to that of low vegetation.(3)The results show that the surface temperature in the study area increases obviously,the minimum temperature rises greatly,and the high-temperature area expands from the main urban area to the surrounding areas,the area of high-temperature area increases significantly,and the change of heat island grade is very obvious.The intensity and scope of heat island effect show a significant increase trend,and the most prominent change is the emergence of a large number of areas from weak heat island to strong heat island It is also accompanied by the emergence of a small number of extremely strong heat island areas.(4)Within the whole urban boundary of Dalian City,the most obvious area of NDVI grade decline is always the center of the city with the largest intensity of urban construction land expansion and the most obvious land expansion.The vegetation coverage level in the peripheral expansion areas of Dalian city has been reduced to varying degrees,and this law is consistent in the direction of urban expansion,which indicates that with the urban land expansion,the density and area of urban vegetation are affected by urban land expansion The results show that the urban heat island effect is caused by the increase of land surface temperature,the grade of heat island effect and the obvious heat island effect.The expansion of urban land is closely related and consistent in direction.