| The world is undergoing intensive urbanization.With increasing populations and socio-economic development,expanding cities has become an important part of land-use change.The key to the high-quality development of cities lies in the“spatial coordination”of the ecological environment relationship within the city and its surrounding areas.The essential is the solution to the contradiction of regional“human-land”relationship.Therefore,the problems of urban expansion and ecological space conflict are not only severe challenges faced by China in the current development,but also hot spots and difficulties in the research of land and space governance.Urbanization has long been recognized as the main driver of many ecological and environmental problems.The Yellow River Basin(YRB)straddles the border zone between the central and western parts of China,Mongolia in the north and the Eurasian Land Bridge in the west.It plays a very important strategic role in China’s economic and social development and ecological security barrier construction.However,the level of regional economic development is low,most of the regions are arid and semi-arid areas,with dry climate,scarce water resources,prominent desertification and soil erosion problems,which is a typical ecologically fragile area.Therefore,it is of great significance to analyze the impact of urban expansion on ecological space.Measure the spatio-temporal evolution characteristics of urban expansion in the YRB.Detect the impact of urban expansion on habitat and construct ecological security.It is of great significance to further carry out multi-scenario land use change simulation research for future regional planning and development.Based on the land use data from 2000 to 2020,combined with land use transfer matrix,standard deviation ellipse,urban landscape expansion index and other methods,we analyze the temporal and spatial evolution characteristics of urban expansion.This paper comprehensively uses the In VEST model and MCR model,and identifies the ecological source area that is different from the traditional sense.“Sources”are obtained from the high habitat quality area by the In VEST model.Combine land use,and natural,social,economic and other influencing factors to monitor and evaluate the habitat quality impact of urban expansion in the watershed.Then,based on land use data and FLUS model,we simulated and predicted the spatio-temporal evolution characteristics of land use in the study area under three scenarios of natural development,ecological protection and sustainable development scenario in 2025 and 2035.The main conclusions of this study are as follows:(1)Grassland,croppland and bareland have always been the main land use types in the YRB,which conform to the basic characteristics of the farming-pastoral zone in the northern arid region.From 2000 to 2020,the land use structure of Jiziwan underwent significant changes,the proportion of construction land increased significantly,the area increased by4.96×10~3 km~2,the growth rate was 148.84%.The urban expansion rate increased from25.95%to 97.58%.In terms of land transfer,the main sources of urban expansion are cropland and grassland.Affected by the differences in regional natural environment,there are obvious differences in the land use structure of different cities.The expansion pattern was mainly the edge-expansion type,expanding along the town center to the periphery,and then changing to the outlying type.(2)The habitat degradation degree is high,and the habitat quality is low of Jiziwan in the Yellow River.Human activities are intense,the ecological environment needs to be improved.Finally,45 important ecological corridors,140 secondary ecological corridors and 44ecological nodes were identified,forming an ecological spatial pattern of“two barriers,three corridors and seven districts”.Restricted by the differences in topography and geomorphology in the study area,most of the spatial trends of ecological corridors distributed in north-south.The spatial network degree of corridors was high in the Daqingshan Ecological Governance Area in the middle of the study area.The spatial density of corridors in the eastern,southern and southeastern parts of the study area was low.The number of ecological nodes was small,and the energy flow,species migration and material exchange between ecological sources were relatively limited.(3)The simulation results of land use change in the Huhhot-Baotou-Ordos-Yulin(HBOY)urban agglomeration show that the simulation accuracy of the land use change model of the urban agglomeration is excellent.The Kappa is 0.87,and the overall accuracy is 92%.The construction land area of the HBOY urban agglomeration experienced a change process of“steady-slow-sharp”increase.The area was dominated by grassland,which accounted for more than 50%of the total land area The expansion pattern is mainly extended expansion,and the sources of expansion are mainly cropland,grassland and other ecological lands.The three scenarios are set up:natural development,ecological protection and economic development.The spatial structure and characteristics of future land use change are obviously different.Under the natural development scenario,urban expansion is unrestrained,and rapid growth occupies a large amount of ecological land.The addition of ecological constraints controls the occupation of grassland and forest.Under the economic development scenario,the urban expansion will further occupy more unused land and cropland.Coordinating the relationship between urbanization and the ecological environment is the only way to promote the new urbanization.In the process of rapid urbanization development,indiscriminate resource encroaching will cause serious damage to the ecological environment.Therefore,in the future,it is necessary to strictly limit the scope of urban expansion,strengthen the protection of ecological land.Reasonable urban planning can effectively optimize the urban spatial structure.Combined with simulation,it can also provide a reference for future land and urban planners.It’s necessary to strictly protect green ecological spacein the future studies.It provides decision-making for the high-quality development of the Yellow River Basin,and improves the modernization level of China’s land space governance system and governance capacity. |
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