Characterization of Tree Canopy in Urban Residential Areas of Beijing

Objective: The paper was aimed to reveal the effect of urban forest in urban areas of Beijing through an analysis of current level of tree canopy in urban areas of Beijing and its variation at different spatial and temporal scales, aiming to discuss the influencing factors of urban tree canopy in residential areas from various aspects, and provide some useful references for urban forest development in residential areas in Beijing and other cities. Method: Based on the 2013 World View 2 satellite imagery of Beijing urban areas from July to September, 2013, and the raster and vector data of urban tree canopy in Beijing 2013 by eCognition 9.0 software was used as data sources. The residential area was selected according to the method of stratified sampling and ecological gradient sampling, and the principle of spatial equilibrium. With the spatial information of urban tree canopy in the sample plots was obtained from ArcGIS platform. In line with field investigation, we discuss temporal and spatial variation of urban tree canopy in urban residential areas of Beijing. Result: The coverage rate of the urban tree canopy of urban residential areas in Beijing was 29.67% of which in different types of residential areas presents as follows: affiliated residential areas(33.96%)>commodity residential areas(30.06%)>resettlement residential areas(20.77%). In different time periods, urban tree canopy of residential areas increased from 29.21% prior to 1980 to 30.7% after 2010. In spatial distribution, the urban tree canopy of residential areas showed that the highest was the northwest of Beijing(40.22%), while the lowest was the eastern part(24.96%). On the loop segment, the urban tree canopy rises in gradient from 21.99% in the second ring to 31.04% in the 1 km outside the 5-6 ring. In the administrative division, it presents that the canopy coverage rate in suburban periphery is higher than that in downtown. The potential urban tree canopy coverage rate was 0.22%, with a small patch of greening land existing in the suburbs. Various factors have an impact on the urban tree canopy in the residential areas, such as the category, completion time, distribution location of residential areas. And it's related to the development of real estate market and urban greening process. Meanwhile, indicators such as plot ratio, housing price, number of households and urban forest structure also have different impacts on urban tree canopy. Conclusion: A certain disparity remains in urban tree canopy coverage was a little lower compared to that of Beijing city as a whole(39.53%). Due to the low potential urban tree canopy coverage, it devitalizes the greening development. In spatial, the tree canopy coverage of urban residential area increases with the expansion of the ring roads while the canopy coverage rate decreases as urbanization increases. In time, remarkable outcomes have achieved in greening process with accelerating urban tree canopy coverage. © 2019, Editorial Department of Scientia Silvae Sinicae. All right reserved.