中国城市群城市用地扩张时空动态特征

Spatio-temporal characteristics of urban land expansion in Chinese urban agglomerations

认识城市群城市用地扩张特征、扩张质量及景观生态效应等综合信息将有助于城市群空间高质量发展规划与决策。选取10个不同发育等级的城市群作为研究对象,综合运用城市用地扩张强度指数、城市用地扩张强度差异指数、景观扩张指数、景观格局指数,分析1990-2015年期间城市群城市用地扩张时空特征及景观生态效应,并构建人口、经济与城市用地协同发展指数,据此分析城市用地扩张中"人-地"关系协同程度。结果表明:①1990-2015年,各个城市群城市用地面积持续增加,建成区的范围不断扩大,扩张强度呈现"上升-下降"的趋势;在2010年之前成熟型城市群的扩张强度最高,2010年之后培育型城市群成为扩张强度最高的类型。②城市群城市用地扩张总体上呈现不均衡布局的趋势,高速扩张区域主要分布在沿海地区。从全国视角来看,东部高于中、西、东北部,整体城市群快速扩张的中心由东向西移动。③城市群城市用地空间扩张模式表现出边缘式和飞地式两种空间扩张模式并存,不同发育等级之间具有明显差异性,成熟型城市群的空间结构较为稳定,其他两种类型的城市群空间结构初具雏形或尚未形成。④城市群城市用地扩张"吞没"了郊区和农村地区,破碎化程度、形状的复杂程度较高,景观格局表现出不稳定。⑤城市群"人口-土地"协同程度逐步增强,"经济-土地"协同程度整体较高,整体上表现出城市用地扩张质量有所提升。新时期城市群城市用地应严格控制扩张规模,加快中小城市的发展,促进城市群城市用地扩张均衡发展,为城市群国土空间高质量发展提供重要参考。

Comprehensive analysis of the characteristics,quality,and ecological effects of urban land expansion would be extremely valuable in high-quality development planning and decision-making.Using data of ten urban agglomerations of China from 1990 to 2015 at varying levels of urban development,this study analyzed the degree of urban land expansion based on the"human-land"synergistic relationship and examined the spatio-temporal characteristics and landscape ecological effects of urban development.Various development indexes for population,economy,and urban land were evaluated,including the urban land expansion intensity index,the intensity differentiation index,the landscape expansion index,and the pattern index.The results of the study are as follows:(1)From 1990 to 2015,the builtup areas in the urban agglomerations expanded continuously,while the expansion intensity showed a fluctuating trend.The highest values of expansion intensity for developed urban agglomerations appeared before 2010,while for the developing areas,the highest values came after 2010.(2)Overall,there was an asymmetrical urban growth among the agglomerations,and the areas with high urban expansion were mainly distributed along the coastal zones.At the national level,the epicenter of rapid urban growth moved from east to west,with the urban expansion in eastern China being much faster compared with the central,western,and northeastern regions.(3)The evolution in urban land use displayed two main spatial patterns,namely edge expansion and outlying,which varied based on the level of urban development.The spatial pattern in the developed urban clusters was more stable,while in the developing areas,the spatial structure started to take shape but have yet to be formed.(4)Urban expansion sprawling over suburban and rural areas resulted in relatively high degrees of fragmentation and structural complexity and instability of the landscape pattern.(5)The man-land synergy in these urban agglomerations increased gradually over time while the economy-land interaction was generally high,indicating an improvement in the overall quality of urban growth.The results of this study highlight the need to have stricter supervision of urban expansion particularly in the early stages of city development,to foster the development of small and middle-sized cities,and to propose a more balanced approach in urban land expansion.The findings here provide valuable lessons for high-quality development of land use in urban agglomerations of China.