Measurement of city tree

Urban areas (cities, towns, villages, etc.) cover 3.5 percent of the 48 conterminous states and contain more than 75 percent of the population. In urban areas, about 3.8 billion trees cover 27.1 percent of the land. On a broader scale, metropolitan areas (urban counties) cover 24.5 percent of the conterminous United States and contain 74.4 billion trees that cover 33.4 percent of these counties. Between 1950 and, metropolitan areas nearly tripled in size; urban areas doubled in size over the past 20 to 25 years.This report is the first national assessment of urban forest resources in the United States and details variations in urbanization and urban tree cover across the United States by state, county, and individual urban area. It illustrates local-scale variation, complexity, and connectedness of the urban forest resource and how this resource changes through time in response to a wide range of powerful forces. The report concludes by outlining future areas of emphasis that will facilitate comprehensive, adaptive, and sustainable urban forest management and improve environmental quality, enhance human health, and connect people with ecosystems in the 21 st century.Keywords: Urban forests, urban forestry, tree cover, sustainability, adaptive management, urbanization, urban ecosystems, urban populations, metropolitan areas, RPA assessment. AbstractPeople are having an ever increasing impact on local, regional, and global environments. This is particularly significant in and around urban areas, where people are often physically or psychologically disconnected from more natural ecosystems. Urban forests and forestry can provide significant benefits to the U.S. population and have the potential to help reconnect the urban population with natural resources and their management. This report is the first national assessment of urban forest resources in the United States. It provides a basis to help develop comprehensive management plans to sustain the urban forest resource and improve environmental quality, enhance human health and well-being, and connect people with ecosystems in the 21 st century.Urban forests are a significant national resource that promise to increase in extent and importance in the years ahead. Metropolitan areas (urban counties) represent the broadest extent of urbanization in the country, including 24.5 percent of the total area and roughly 80 percent of the total population in the 48 adjacent United States. With an average tree cover of 33.4 percent, metropolitan areas collectively support nearly onequarter of the Nation's total tree canopy cover-some 74.4 billion trees. Trees found in urban areas (cities, towns, and villages) also comprise a substantial portion of the Nation's resource base. Covering 3.5 percent of the total area and containing more than 75 percent of the total population, urban areas support trees that account for 2.8 percent of the total tree canopy cover in this country-about 3.8 billion trees. The average percentage of tree canopy cover for both metropolitan areas (33.4 p...

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Trees sequester and store carbon in their tissue at differing rates and amounts based on such factors as tree size at maturity, life span, and growth rate. Concurrently, tree care practices release carbon back to the atmosphere based on fossil-fuel emissions from maintenance equipment (e.g., chain saws, trucks, chippers). Management choices such as tree locations for energy conservation and tree disposal methods after removal also affect the net carbon effect of the urban forest. Different species, decomposition, energy conservation, and maintenance scenarios were evaluated to determine how these factors influence the net carbon impact of urban forests and their management. If carbon (via fossil-fuel combustion) is used to maintain vegetation structure and health, urban forest ecosystems eventually will become net emitters of carbon unless secondary carbon reductions (e.g., energy conservation) or limiting decomposition via long-term carbon storage (e.g., wood products, landfills) can be accomplished to offset the maintenance carbon emissions. Management practices to maximize the net benefits of urban forests on atmospheric carbon dioxide are discussed.

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