Unrevealing the process and driving factors of urban construction land expansion in the middle reaches of the Yellow River,2000-2020
Studies on urbanization is of great significance to the sustainable utilization of regional land resources,ecological environmental protection,and food security.Existing studies are less on the vertical expansion of urbanization under complex landscapes,while the urbanization research at different time scales,especially at the county scale,needs to be further strengthened.The surface slope of the middle reaches of the Yellow River(MRYR)varies greatly,and the expansion process of urban construction land at different scales and its driving factors are still unclear.Based on the multi-period remote sensing image data of the MRYR,this study explores the distribution pattern of urban construction land in different slope gradients according to the slope spectrum of construction land,and analyzes the influencing factors of the variation of urban construction land area under different topographic conditions based on the structural equation modeling.The results of the study show that:(1)Regional urban construction land has expanded significantly in the past 20 years,especially in the period of 2005-2010;among them,the urban construction land in the sandstorm area(SA)and loess hill and gully area(HGA)has expanded most significantly.(2)Regional urban construction land expands vertically to areas above 5°,and the peak values of regional urban construction land climbing appeared in the period of 2005-2010;the obvious phenomenon of urban construction land climbing was observed in the loess hilly and gully areas(HGA)and soil/rock mounts area(RMA).(3)At the county scale,the number of slope-climbing counties accounts for 68.45％of the total of regional county seats,of which 37.38％belongs to the high slope-climbing type;the larger proportion of slope-climbing urban areas appeared in the RMA,and the lower proportion of slope-climbing urban areas appeared in the loess plateau hilly area(PHA).(4)However,population density,economic development level and other factors have significant impact on the expansion process of urban construction land,while there are gradient differences in slope,slope direction and elevation in the influence of different natural environments and socio-economic factors.(5)The encroachment of gentle cultivated land by urban construction land is alleviated in the high slope climbing area,while the problem remains serious in the lower slope climbing area;urban construction land climbing can effectively alleviate the impact of construction land on gentle ecological land.The results of the study provide important information of the development strategy of high-quality urbanization,sustainable development,ecological environment improvement and human-land relations in multi-terrain complex landscape regions.
urban expansiontemporal and spatial distributionclimbing uphillslope spectrumcontrolling factors
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