Spatial-temporal Evolution And Ecological Effects Of Land Use In Changchun Urban-suburb Areas

With the increasing demand of the people for beautiful ecological environment,the concept of "green water and green hills are Jinshan and Yinshan" is deeply rooted in the hearts of the people.It is imperative that the effects of ecosystem services of land use should not be reduced as a constraint for economic development.Traditional studies on land use and ecological effects mostly focus on regional and municipal areas,but neglect the study of urban rapid development zones.Therefore,this paper takes the rapid urbanization of Urban-Suburb in Changchun as an example.Based on remote sensing images,the distribution of land use types in four years of 2001,2007,2011 and 2016 was obtained,and the spatial-temporal changes of land use in the study area between 2001 and 2016 were analyzed.Supported by land use type data,the spatial-temporal changes of ecosystem service value in the study area were measured,and the distribution of ecological risk grade in the study area was analyzed,aiming at providing scientific reference value for the new urban ecological construction and urban planning in the rapid urbanization area.The main conclusions are as follows:(1)The land use types in the study area have always been dominated by grassland and construction land,the sum of the two occupies more than 3/4 of the total area.The change of land use types has gradually changed from grassland-based to construction land-based.The newly added construction land mainly distributes in the peripheral areas of the original construction land and develops in an expansive way;The proportion of grassland,cultivated land and unused land continued to decrease,while the proportion of forest land and water area increased first and then decreased.(2)The comprehensive dynamic degree of land use in the study area increases first and then decreases.From 2007 to 2011,the comprehensive dynamic degree of land use is the highest and the degree of change is the sharpest.The comprehensive index of land use degree in the study area has obvious spatial differentiation,showing the overall distribution characteristics of high in the middle and low around.The urban land use pattern has gradually changed from extensive type to filling type,and the circular distribution characteristics are more prominent.(3)The total value of ecosystem services in the study area showed a downward trend.During 2001-2016,the total value of ESV decreased by 33.1%,with an average annual decline rate of 2.2%.The contribution rate of grassland and water to the total value of ESV was the highest,showing an increase as a whole.The single value of ecosystem services in the study area declined,among which hydrological and climatic regulation contributed the most to the total ESV.The proportion of ecosystem services in the study area continued to rise,while the proportion of supply services,support services and cultural services decreased in varying degrees.(4)The ecological risk grade of the study area has changed from low-risk area to high-risk area,and the distribution of ecological grade has declined from northwest to southeast,with the former high-risk area as the core gradually expanding eastward and southward,which is consistent with the expansion direction of urban construction land.