Over 70% of the population in developed countries live in cities. World wide, the average urban population proportion is 42% (World population reference, 1993). Urbanization creates significant changes in land use and land cover, affecting the structure, pattern and function of the ecosystem. The public is increasingly concerned about how these changes influence our daily life and the sustainability of "quality of life" for future generations. The structure and function of urban ecosystems can be studied using the same methods as the study of natural environments. Vegetation canopy, pavement, and buildings are the three important land cover types that affect the development of the urban ecosystem. The trees planted in urban settings along streets, in yards and parks are described as an urban forest, and they are an important part of the urban ecosystem. Urban trees play an important role in landscape beautification, in reduction of air pollution, and in moderating the urban energy budget, water use, and storm runoff. Increasing the proportion of pavement area during the process of urbanization strongly influences energy exchange, hydrology, and micro-climate (Arnold et al., 1996). Many problems facing management of the urban ecosystem are related to these factors. For example, urban heat island effects and increased storm runoff are related to the imperviousness of pavement and buildings. Air quality and water use are related to crown density and tree density. Air quality, energy partitioning, and hydrologic processes in the urban ecosystem depend on knowledge of tree species, leaf and stem surface areas, tree dimensions, percent of pavement cover, among other things. To understand how urban forests function and to estimate the value of their environmental services we must first recognize properties related to forest structure. Also, a good understanding of the structure of the urban forest provides information useful for urban managers, such as for planning tree pruning, leaf removal, and insect or disease control activities.
This study was used to find species composition of Urban Trees. I've only included the Introduction section but the whole PDF of study is available here.