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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.

Urban tree debris generation and damage resulting from seven hurricanes during the 2004 and 2005 Florida hurricane seasons was analyzed using a random sample of communities in highly affected counties. Woody debris amounts, rates, and costs for cleanup were quantified, as were the spatial patterns of damage across the state. Average debris volume per mile of street segment was 488 cubic yards, and cost of removal and disposal averaged $21.50 per cubic yard. Urban forest structure, community characteristics, and hurricane severity influenced debris and cost results. Spatial analyses indicated that debris results were clustered into northwest and southeast areas of the state, which represent two distinct ecoregions in Florida. Although southeastern Florida had much higher costs per cubic yard than the northwest, the debris volume per road mile was higher in the northwest portion of the state. On a per-mile basis, Hurricane Ivan was responsible for the greatest debris volume, and Hurricane Katrina was the most expensive. These results can be used to help communities plan for hurricane response and management activities and to estimate potential damage to their urban forest resource.

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