2000—2020年间黄河中游不同地貌区城镇建设用地扩张过程及其影响因素

Unrevealing the process and driving factors of urban construction land expansion in the middle reaches of the Yellow River,2000-2020

城镇化研究对区域土地资源可持续利用、生态环境保护、粮食安全保障具有重要意义。现有研究对复杂地貌下城镇垂直扩张开展较少,而不同时间尺度尤其是县域尺度下的城镇化研究更有待进一步加强。黄河中游(MRYR)地表坡度变化大,其城镇建设用地在不同尺度上的扩张过程及其驱动因素尚不明确。本研究基于黄河中游的多期遥感影像数据,借助建设用地坡谱探讨不同尺度下城镇建设用地在不同坡度梯度上的分布格局,运用结构方程模型解析了不同地形下城镇建设用地面积变化的影响因素。结果表明:①过去20年区域城镇建设用地水平扩张显著,尤以2005—2010年间最为显著;其中风沙区及黄土丘陵沟壑区城镇建设用地水平扩张最为显著。②区域城镇建设用地出现向5°以上区域垂直扩张的趋势,城镇建设用地爬坡高峰期在2005—2010年间;黄土丘陵沟壑区和土石山区的城镇建设用地爬坡现象尤为显著。③在县域尺度上,爬坡型县域的数量占区域县域城镇总数的68.45%,其中37.38%为高爬坡型;爬坡型城镇占比较大的是土石山区,较低的是黄土高塬(海拔较高的塬面)沟壑区。④人口密度、经济发展水平等因素对城镇建设用地面积变化产生显著影响,而不同自然环境、社会经济因素的影响存在坡度、坡向、海拔的梯度差异。⑤平缓耕地被城镇建设用地侵占的现象在高爬坡地区得到缓解,而在低爬坡地区该问题依旧严峻,同时城镇爬坡可有效缓解城镇扩张中对平缓生态用地的多度侵占。研究结果可对多地形复杂地貌区域的高质量城镇化发展策略、可持续发展、生态环境改善和人地关系协调等提供重要参考。

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.