| In today's domestic urbanization process,in order to meet the requirements of growing population survival and production-construction,urban space also needs to continue to extend outward.As a result,urban expansion has increasingly become the dominant feature of land use change,and it has also put greater pressure on the maintenance of urban ecological space quality.Therefore,our government has put forward the overall requirements for the construction of' ecological civilization,emphasizing that more consideration of man-land harmony and green development should be added to the future urban development planning.In this context,it is necessary to change the current extensive use of land resources,carry out a prospective study on the future layout optimization of urban land,and explore a new urban development path which is more in line with the requirements of the times.Changzhou is one of the core cities in the Yangtze River Delta.It is of great significance to study Changzhou as a typical region for the urban development of the eastern economically developed areas.From the perspective of coordinating urban growth and ecological environment protection,this paper models the future urban spatial evolution based on cellular automata model,and integrates the land ecological suitability constraints into the process of urban expansion to coordinate and guide the spatial pattern,so as to reduce the arbitrary encroachment of cultivated land,water and other ecological land.In the process of acquiring the rules of cell transformation,the integration strategy based on stacking is adopted to fuse multiple machine learning models,which further improves the ability of spatial data mining,thus realizing the improvement of cellular automata model.Finally,the paper also forms a future urban spatial development optimization scheme.Local governments can take this as a theoretical support in the compilation and implementation of land spatial planning,and carry out spatial implementation according to the specific development plans.The major contents and conclusions of the thesis are listed below:(1)Analysis of the process of urban land expansionDuring the period of 2009-2015,the urban land in the study area increased by 64.31 km2 and the scale of increase showed a decreasing trend.The southern and northern parts of the study area are the main directions of urban land expansion,that is,Wujin District and Xinbei District are the main areas of new urban construction.The analysis of multi-ring buffer zone shows that the proportion of urban land in each circle is increasing,and the expansion intensity of urban land in the later period of time series is decreasing,which is consistent with the decrease of the scale of newly added urban land.In terms of urban land expansion mode,enclave and marginal growth hold the dominant position.The above results show that although urban growth has slowed down,there is still a clear trend of"outward expansion"on the whole.In the process of urbanization during this period,a large number of ecological land,such as arable land and water,were occupied,and the carbon storage of the study area also reduced by 6.35*105 tons.(2)Computation of land ecological suitability constraintsIn this paper,11 indicators are selected from three perspectives:natural geographical conditions,human activity stress and ecological function area limitation.The corresponding weights of different indicators are obtained based on analytic hierarchy process.Finally,the multi-factor comprehensive evaluation of land ecological suitability of the study area is carried out.The evaluation results show that the areas with high ecological suitability are located in the southwest,southeast of Wujin District and north of Xinbei District,which are mainly high-quality basic farmland or important water bodies and ecological public welfare forests.In addition,using the evaluation results as resistance base data and urban land of 2015 as expansion source data to input to the minimum cumulative resistance model,the spatial map of land ecological resistance constraints for urban expansion was generated.(3)Construction of urban expansion model based on cellular automataIn view of the shortcomings of the existing research of urban expansion simulation model based on cellular automata and single machine learning model,the ensemble strategy of stacking is adopted to integrate three models:support vector machine,random forest and multi-layer perception machine,which could improve the accuracy and efficiency of acquiring conversion rules of new urban land,and the capability of spatial data mining.In addition,the data of land ecological suitability constraints and urban expansion process are coupled into the same framework,and a simulation model of urban land expansion under land ecological suitability constraints is constructed.(4)Simulation and optimization of urban land expansion in the futureThe urban land distribution in the study area in 2030 was predicted,and the current situation continuation scenario,balanced development scenario and strict constraint scenario of different land ecological suitability constraint intensity were compared and analyzed.The results show that the ecological suitability of land can effectively guide and restrain urban expansion and optimize land use structure.Moreover,with the enhancement of constraint intensity,the spatial layout of urban land becomes more compact,and the ecological land area occupied by urban land,such as arable land and water body,is significantly reduced,and the expansion hot spots are further away from the important ecological land.Finally,the paper also extract important ecological core region based on the evaluation result of land ecological suitability,combined with the balanced development of scenario simulation analysis on urban sprawl in 2030 to design a comprehensive optimization schemed for urban space development.It is significant for providing the local administration more flexible and comprehensive strategic support in the actual national spatial planning and implementation of regional policy. |
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