| Land source is the foundation material of human survival and development, however, along with the advancement of urbanization, population grew rapid, the degree of land use increased, the land ecological problems highlighted increasingly, pose a serious threat to social development and regional ecological security. Land ecological security is the outcome of combined action of natural environment and social economic factors, land use change caused by urban expansion plays a decisive role. Built a land ecological security evaluation model based on urban expansion,assure the relationship of LUCC process,pattern of urban land expansion,and land ecological security; get a comprehensive assessment of regional ecological security of land use change characteristics,provide a scientific basis for effective prevention and control area of land ecological security problems and sustainable development.This paper, by using 1995, 2005 and 2015 the third phase of remote sensing image in mianzhu, based on the field investigation data and supervised classification method to extract the land use data, establish the land use spatial-temporal database, analysis the land use changes in spatial and non-spatial characteristic. Urban extension characteristics of Mian-zhu city was analyzed by urban expansion model based on land use data, then choose indicators to set up ecological security evaluation model according to the characters of natural, economic and social development. Principal component analysis(PCA) is used to calculate index weight, and ultimately to classify and evaluate the hierarchy of land ecological security in mianzhu city, ensure the the relationship and response between urban expansion and land ecological security. The results show that:(1)Over the past 20 years, land use quantity, type, structure and spatial distribution changes have taken place in mianzhu city, land use changed significantly. During the study period, area of construction land increased significantly, woodland area keep stable, cultivated land area declined, water and grassland area changed little, unused area increased considerably. And the area of the various land use types in different period have different degrees of increase and decrease.In terms of land use spatial distribution, the cultivated land into construction land mainly occurred in the east side to the southeast plains; Cultivated land into forest land, mainly in Jiulong town, Hanwang town and Wudu town such as the transition areas of plain and mountainous. Forest land into unused land occurred in the northwest mountain region of Qingping township and Jinhua town. Construction land transfer into cultivated land distributed mainly in the plain area.(2)Significant urban sprawl, construction land area has doubled in 20 years, especially in the azimuth III, expansion trend is obviously toward southeast, and show a different expansion trend and characteristics of different period of time.During 1995-2005,built-up land rising at an annual rate of 228.158 hm2,then grow in 415.664 hm2 per year during the period of 2005-2015. Outward from the city center, with the increase of buffer radius, gradually reduce the proportion of construction land, cultivated land ratio gradually increased. Urban land expansion major to the east and southwest. From 1995 to 2005, the expansion of the urban land utilization is mainly in the east side to the southwest direction; In 2005-2015, expand obviously appear in the southeast of the city heart and the of northeast and southwest town of Dongbei and Xinan.(3)Land ecological security level in Mianzhu city were divided into four levels: security, safer, and general security and safety;The security level accounted for 47.26% of the whole city area, general safety level of 35.14%,safer and not safe level respectively accounted for 10.06% and 7.55%. Correlation analysis was made in extension of urban land with the land ecological security situation,the land ecological security situation were negatively correlated to urban expansion condition. |
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