北京市第一道绿化隔离区树冠覆盖特征与景观生态变化

Urban Tree Canopy Changes Explained by Landscape Ecological Perspective:a Case Study of First Green Belt in Beijing,China

【目的】以北京市第一道绿化隔离区建设为例,利用高空间分辨率的航、卫片信息源,分析城市林木树冠覆盖特征,力图一方面准确揭示北京市第一道绿化隔离区的生态建设成效,另外也试图从景观生态学视角揭示其格局内在变化过程与趋势,进而为北京市及其他城市未来的生态建设提供借鉴。【方法】以0.5 m分辨率的2002年航片和2013年的worldview2卫片为基础,利用econgnition面向对象的解译技术平台,以城市树冠覆盖为核心,利用景观生态学的分析方法,从景观动态、景观格局变化和景观斑块尺度变化等方面,探讨一道绿化隔离区内的林木树冠覆盖特征。【结果】一道绿化隔离区林木树冠覆盖面积从2002年的4 832.98 hm^2增加到了2013年的10 095.01 hm^2,11年间共增加了20.57%;绿地率净增23.94%,生态用地率净增24.11%;斑块平均分维数和斑块面积形状指数呈现不断增加的特点;小型斑块和巨型斑块的数量和面积变化幅度最为显著,11年间数量分别减少了42 286个和130个,面积分别减少了186.08和5 457.75 hm^2;城市总体规划、2008奥运会的绿色需求、城市公园环建设决策和首都百万亩平原大造林是其变化的最重要驱动因素。【结论】与建设之初相比,一道绿化隔离地区内的林木绿地斑块更趋向于向自然化的方向变化,同时斑块规模呈现了小、中、大型斑块数量与面积同步减少,而特大型斑块与巨型斑块的斑块数量和面积同步增加的变化趋势。第一道绿化隔离区域城市林木和绿地不仅取得面积上的急速扩大,而且其在城市生物多样性保护中的作用也越来越大、越来越突出。

[ Objective ] The construction of urban green beh is one of the most effective approaches to preventing chaotic urban sprawl and ensuring the urban ecological security. In this research, we used tree canopy of urban forest to explore the temporal and spatial ecological effectiveness of the first green belt in Beijing from a perspective of landscape ecology. To reduce the errors of low spatial resolution remote sensing data, we used high-resolution aerial and satellite images to extract the forest canopy data thanks to the recent advancement in high resolution remote technology. [ Method] Based on 2002 aerial photo and 2013 Worldview2 images with a resolut sensing ion of 0.5 meter, the urban forest canopy of 2002 and 2013 within the first green belt were interpreted by using the object-oriented interpreting technology platform eCognitiong. 0 software. Urban forest canopy within in the first green belt area was analyzed in detail from several aspects including landscape dynamics, changes of landscape pattern and scale of landscape patches. [ Result ] Result indicated that urban forest canopy within the first green belt area increased from 4 832.98 hm^2 in 2002 to 10 095.01 hm^2 in 2013, equivalent to 20.57% over this years. Overall, the proportion of green land was increased by 25.94% and the proportion of ecological land increased by 24.11%. From a perspective of landscape pattern change, the MPFD and MSI index of urban forest canopy patches increased constantly. From a perspective of scale changes on patch size, small and giant patches were two most significant types, which decreased respectively by 42 286 and 130 in number, and 186.08 hm^2 and 5 457.75 hm^2 in area over 11 years. Such dramatic changes were driven by several factors including overall urban planning, and open space demand for hosting the 2008 Olympic Games, promoting the urban park development by the authorities of city, and ultimately leading to the huge urban greening project entitled with ＂ One Million Mu Plain Afforestation Project＂. [ Conclusion] Compared with the initial stage of construction, the development of urban forest canopy patches within the first green belt tends to be more natural. In the meantime, there was a changing trend that the number and area of small patches, medium patches and large patches reduced while the number and area of extra-large patches and giant patches increased synchronously. All of these trends showed that the urban forest canopy and green space of this area have achieved a rapid expansion in the area, and the belt played a more and more important role in the protection of urban biodiversity as well.