| The various land use changes triggered by urban expansion are essentially spatial competition of land in different period and under different policies.The issue of coordination between urban expansion and ecological protection has become the core and difficulty in the practice of territory spatial governance.As an important gateway of the West region toward the Middle and East region in China and a key region with fragile ecological environment and intensifying resource constraints,the Guanzhong Plain Urban Agglomeration faces more significant land ecological security issues and resource stress.The formulation of the "Guanzhong Plain Urban Agglomeration Development Plan" in 2018 also indicates that coordinated,green and sustainable development will be one of the priorities for the future development of the Guanzhong Plain Urban Agglomeration.Moreover,the urban fringe area,as the areas with the most drastic land changes and the most severe ecological stress in the urban agglomerations,need more research and attention.Therefore,it is important to analyze the land use changes from macro to micro scales in urban agglomerations,to comprehensively compare the impacts of urban expansion on different ecological land,and to further conduct multi-scenario land use change simulation studies for the future planning and development of urban agglomerations.Based on the land use data from 1990 to 2018,this paper divides farmland into artificial ecological land,and regards forest land,grassland,water bodies,and unused land as natural ecological land.Combining the land use transfer matrix,comprehensive land use dynamics,landscape index and other methods,the direct and indirect impact of urban expansion on ecological land is analyzed.After that,this study builds the urban agglomeration land use simulation model based on spatial interaction(UALUSM-SI)by combining the urban flow,Cellular Automata,random forest,Markov chain,and minimal cumulative resistance model to simulate land use changes under four scenarios: natural development,farmland protection,ecological constraints,and comprehensive protection.The main conclusions of the study are as follows:(1)There are obvious differences in land use structure and changes at different scales in the study area.The area of built-up land increased significantly from 1990 to 2018.And the change of farmland and other natural ecological land is characterized by "see-saw" development.Farmland,forest and grassland are the main land use types in the urban agglomeration,but due to differences in the regional natural environment,there are obvious differences in land use structures in different cities.The urban fringe areas are mainly farmland and built-up land.Affected by the policy of farmland occupancy-compensation balance,the area of farmland in the urban agglomerations increased temporarily from 1995 to 2000,and the farmland change in some cities was similar to that of urban agglomeration.After 2000,policies and concepts such as returning farmland to forests,ecological protection red lines,and ecological civilization were put forward,and the area of natural ecological land such as forest and grassland increased slightly,while the area of farmland declined.(2)The main source of newly added built-up land is farmland.Over time,the fragmentation of farmland increased and connectivity decreased.The built-up land expansion has a greater impact on the farmland landscape than forest and grassland.Among them,the land use changes in urban fringe areas are the most severe,and the loss of farmland is the most serious.The land use transfer between urban agglomeration and different cities is similar.Affected by the farmland occupancy-compensation balance policy,the main source of farmland compensation for urban agglomeration and prefecture-level cities is grassland,followed by forest land.The indirect impact of built-up land in different cities on natural ecological land is affected by the compensation mechanism of farmland.Therefore,it is unreasonable to implement a unified farmland compensation policy for the entire region.It is necessary to consider regional land resource conditions,and appropriately adjust development and restraint policies,which is conducive to the sustainable development of the urban agglomeration.(3)The land use simulation results of Guanzhong Plain Urban Agglomeration in 2015 show that the UALUSM-SI has a good simulation accuracy,with an overall accuracy of 89.76%and a kappa coefficient of 0.8501.Comparing the simulation results of different scenarios,it is found that unconstrained expansion of built-up land will squeeze a large amount of ecological land,but the farmland protection or ecological constraints scenario will also sacrifice other ecological land types and cause a large amount of natural ecological land or farmland loss.The comprehensive protection scenario that integrates farmland and ecological protection not only restricts the expansion of built-up land,but also effectively reduces the loss of ecological land including farmland.However,all scenarios indicate that the built-up land expansion will inevitably lead to the loss of ecological land.Therefore,the scale of built-up land development should be controlled,and the sprawling expansion of built-up land should be appropriately adjusted to vertical development based on the natural environmental conditions of different regions.Besides,delineating a clear basic farmland red line and ecological protection red line will be of great significance to the coordination and green development of urban agglomeration. |
PDF Full Text Request