城市景观破碎化格局与城市化及社会经济发展水平的关系——以北京城区为例

快速城市化引发的景观破碎化加剧对于城市生态系统的过程、功能及其所提供的生态服务功能具有显著的影响。以北京市五环内中心城区为例,采用移动窗口分析、梯度分析与景观指数相结合的方法研究了城市景观破碎化的空间分布格局和内部水平差异,并以此为基础,探究景观破碎化与城市化及社会经济发展水平的关系。结果表明:类型水平上,城市建筑用地景观比例达63%,斑块连通性好,破碎化程度低,而绿地景观占33%,斑块分布不均匀,破碎化程度较高。景观水平上,城市中心和郊区的景观破碎化程度要明显低于城市边缘的城乡过渡区,沿城市化梯度从中心向外围呈现出先上升后下降的趋势。回归分析结果表明,景观破碎化程度与城市化水平之间表现出一种倒"U"型关系,并在城市化水平达42%—45%之间,景观破碎化程度达到峰值。进一步研究表明,人口密度和家庭户数是导致景观破碎化加剧的直接驱动因素,而经济的快速增长对景观破碎化程度的提高具有间接的影响。该研究结果不仅能作为城市生态系统监测的重要指标,还能为城市景观的合理规划提供科学依据,而且对于促进城市的可持续发展具有重要的意义。

The spatial pattern of landscape fragmentation and its relations with urbanization and socio-economic developments: a case study of Beijing

Substantial attention has been focused on the phenomenon of landscape fragmentation in urban environment that stems from rapid urbanization and social-economic developments. Intensification of landscape fragmentation is increasingly considered as an essential ecological indicator that strongly influences the processes, functions, and services of urban ecosystems. Hence, in this study, on the basis of the interpreted land use map from high resolution SPOT XS imagery, we utilized a series of moving-window analysis and gradient analysis combined with selected landscape metrics to investigate the spatial distribution and local differences of landscape fragmentation; and further examined its relations with urbanization and social and economic developments in Beijing urban region, China. The result shows that, at the patch level, urban built-up lands occupied 63% of the entire study area and were well-connected, and less- fragmented. Whereas urban green lands constituted 33% of the area, with the characteristics of uneven distribution, and relatively high fragmentation status. At the landscape level, we found that landscape fragmentation, indicated by metrics of patch density (PD), edge density (ED) and landscape division index (DIVISION), was considerably higher in urbanizing fringes than urban central and rural areas. In the eight directions along the urban-to-rural gradient from the urban center outward, the degree of landscape fragmentation rose initially and fell down afterward, displaying a single peak pattern in urban fringes. Regression analyses indicate that the relationship between the degree of landscape fragmentation and the level of urbanization is significant in form of binomial equation and emerging as inverted "U" pattern in the diagram, exhibiting a threshold for the increase of landscape fragmentation when the degree of urbanization approached 42%-45%. Identification of this threshold suggested that urbanization could pose both positive and negative effects on landscape fragmentation; that is below the threshold, urbanization has positive effects whereas above the value, it imposes negative effects on landscape fragmentation. Further investigations revealed that the social factors of population density and the number of household were the primary direct drivers of landscape fragmentation; while rapid economic development, which accelerates urbanization, has imposed indirect impacts on the intensification of landscape fragmentation. This study developed a framework for analyzing and enhancing our understanding of the nature of landscape fragmentation. Our derived results not only could be used as an important tool for assessing the spatial pattern of urban ecosystem, but also provided scientific basis for effective landscape planning and design of sustainable urban environment.