Spatial-temporal Dynamics Of Urban Expansion In Changchun City During 1970s-2015

Urban construction land information is an important factor reflecting land use/cover change.It not only plays an important role in the study of city expansion dynamic change,city food crisis,and urban ecological environment etc.,but can provide data support for urban ecological assessment,urban pollution prediction,government planning and building sustainable city and other aspects.Changchun is the capital city of Jilin Province,and the administrative center and industrial center.The study area contains Nan guan District,Kuan cheng District,Chao yang District,Er dao District,Lu yuan District and 5 municipal districts,and uses object-oriented method and NDBI index to obtain land use in formation of the study area.Finally,the construction land information in1974,1983,1990,2000,2010 and 2015 has been obtained.The collected results of land use information in Changchun have been used to analyze factors of urban expansion spatiotemporal dynamics and urban expansion motivation,so as to provide an important scientific basis for understanding the expansion process of the cities in northeastern China.At the same time,it also has an important reference value for urban land use planning and management.This paper uses six remote-sensing images including Landsat–1?3?4?5?8 from the 1974 to 2015 as the basic data source,and adopts object-oriented and NDBI index classification method to obtain urban construction land information of the research area in the year 1974,1983,1990,2000,2010 and2015.Combined with the annual expansion index model,urban land use spatial distance transfer model,convex-hull principle,temporal and spatial variation gradient differentiation model,distance decaying density model and Mark off land use transfer matrix method and soon,study the expansion speed,strength,spatial focus transfer,type,direction,spatial structure and land use type transfer and other characteristics of Changchun city research area from the 1974 to2015.The results show that,from the view point of urban expansion speed,urban construction land area in Changchun increases 257.39km² from the 1974 to2015,only a total of 45 years.The city develops from low speed expansion to high speed expansion,and gets faster step by step.From 2000 to 2010,the expansion speed of construction land in Changchun is the fastest,which obtains a total increase of 154.90km² and accounts for 60.18%of total expansion area among these 45 years.From the view point of urban spatial focus transfer,it over all develops from the northwest to the southeast over these 45 years.From the view point of urban expansion type,they are respectively filling type,extension type,filling type,extension type,filling type for the 1974 to 1983,1983 to 1990,1990 to 2000,2000 to 2010 and 2010 to 2015.From the view point of directional characteristics,the expansion direction of the study area keeps change in different periods,of which the year 1974 to 1983 mainly expands to all around,1983-1990 to the south,the southwest and the southeast,1990-2000 to the west,the southwest and the southeast,2000-2010 to the west,the south,the southwest,the southeast and the northeast,2010-2015 mainly to the southwest.Over all speaking,the expansion direction of study area in Changchun mainly goes towards the south and the northeast,which is related to southern migration of municipal government and the establishment of northern New Area.From the view poin to fland use type transformation,the area of residence,traffic land,other urban construction land and green belt in the study area keeps increasing over these 45 years.Further more,there is a mutual transfer of different levels among these 4 construction lands.The urban expansion land mainly comes from agricultural land,suburban green space and suburban wet land around the city,of which over 92%of these non-urban land turns into residence.From the viewpoint of urban expansion driving force,the factors mainly include natural factor and anthropogenic factor,among which human factor acts as the main driving force,followed by natural factors.