Abstract: [Objective] The construction of urban green belt 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 eCognition9.0 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 hm² in 2002 to 10 095.01 hm² in 2013, equivalent to 20.57% over this years. Overall, the proportion of green land was increased by 23.94% 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 hm² and 5 457.75 hm² 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.

Key words: first green belt, urban tree canopy dynamics, landscape pattern changes, Beijing