Study On Land Use Change And Its Effects On Eco-Environment In CZT Core Region

Land use change is the current frontier and hot topic of global environmental change. Meanwhile, promoting the new urbanization is a strategic initiative of CPC and the government at the new era. Study on Changsha-Zhuzhou-Xiangtan(CZT) core region-a typical rapid urbanization of agglomerations will impose great significance on the land change of the area and its ecological effect. In this paper, CZT core region is selected as the research object to screen the optimal land use information extraction method by means of field observation and laboratory test with the remote sensing image of 2000,2007 and 2013 as the main data source. The space-time evolution process of land use in CZT core region is analyzed by using analysis indicator of land use structure change, analysis indicator of land use direction and analysis indicator of the space of land use with "time" and "space" as the main line.On the basis of building GIS-Logistic regression model, the major driving factors and mechanism of land use change in CZT core region is revealed from both natural and socio-economic aspects. The surface temperature of the study area is obtained by inversion of radiative transfer equitation method, in order to study the association between the spatial distribution of thermal field, land use type and the surface temperature in the CZT core region reveal the contribution of land use type to thermal environmental effect and explore the thermal environmental response of land use change. By establishing RSEI index model based entirely on remote sensing information, the quality condition of ecological environment in CZT core region is evaluated quantitatively.In the process of study, the following conclusions and progress are obtained:(1) The information extraction solution of optimal land use is selected. The land use types in CZT core region are identified as five categories:farmland, woodland, grassland, water body, and construction land. The experiment results show that CART is the optimal classification scheme under the condition of 75% training sample size and adding texture. The scheme is a kind of more effective information extraction method of higher precision with a total classification accuracy of over 92% and Kappa coefficient of over 0.9.(2) Current situation of land use in CZT core region is defined. As of 2013, the land use structure in the study area is still dominated by farmland and woodland, accounting for more than 3/4 of the total land area. The construction land is less than 1/5 of the total area. The grassland and water body takes up a little area. Compared to 2000, the proportion of farmland and woodland has substantially decreased, however, the sum of index of abundance still reaches to 58.68% and the sum of importance is still more than 76.58%. Additionally, the abundance and importance of farmland still exceeds 20% and that of construction area is rapidly increased and close to 20%, which indicates that the study area is in the stage of development shifted from predominately agriculture to primarily industry and services.(3) Characteristics of land use change in CZT core region are clarified. The study area is mainly characterized by the sharp decrease of farmland and woodland and the rapid expansion of construction land from 2000 to 2013; Generally, the land use utilization is higher and shows a slow upward trend year by year. The land use index of 2000,2007 and 2013 is 301.85,308.86 and 311.38, respectively. Both the variation and rate of land use during 2000-2007 and 2007-2013 is greater than zero, indicating the development of land use. The conversion of land use types varies in districts and counties. In general, the between-class conversion of ecological degradation is more significant than the ecological improvement.(4) Driving mechanism of land use change in CZT core region is analyzed. The situation of land use change in the study area is the result of long-term effects of natural environment and human economic and social activities. The location factors, DEM elevation, and rivers are the natural foundations of the land use change, which determines the changes in spatial form. The construction of roads, railways and other infrastructure expands the areas of changes in types of various lands use. The economic and social factors such as GDP, population and fixed investments determine the speed of changes in various lands use.The policy planning controls the direction, size and development of types of various lands use.(5) Relation between land use change and thermal environmental effect is revealed. In the study area, the contributions of land use types to the heat island effect are different. The construction land has greatest contribution to the intense heat and strong heat island, and the woodland and water body has greatest contribution of the green island. The focus of the urban built-up area is always shifted from the southeast to the northwest. The general shift of the heat island plaque is firstly from northeast to southwest, and then to northwest. The shifted direction of the heat island roughly matches with the shifted direction of the urban focus. The heat island effect and NDVI presents a negative correlation. The NDVI value decreased by each 0.1 will increase the surface temperature by 2.02℃. The heat island effect and NDBI presents a positive correlation. The NDBI value increased by each 0.1 will increase the surface temperature by 1.33℃. The heat island effect and MNDWI presents a negative correlation. The MNDWI value decreased by each 0.1 will increase the surface temperature by 1.55℃.(6) The ecological environment quality of the CZT core region is assessed. The RSEI model consisting of 5 full-sensing indexes such as NDVI, LST, MNDWI, NDSI and AOD is constructed to obtain the ecological environment quality index of the study area in 2000, 2007 and 2013 is 0.7005,0.6778, and 0.7174, respectively, indicating that the ecological environment quality of research area comes through a change process with "good-poor-good" and maintains a consistent trend with the variation of types of ecological degradation and ecological improvement.(7) This study proposed some suggestions which are top design of spatial restructuring in guide area, improvement of the level of urban development, environmental dynamic monitoring to construct a gorgeous CZT core region.