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Wednesday, April 11 • 4:30pm - 4:45pm
SYMPOSIA-15: Structure, Function and Value of Urban Forests in California

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AUTHORS: E. Gregory McPherson, USDA Forest Service, Pacific Southwest Research Station; Qingfu Xiao, University of California, Davis; Natalie S. van Doorn*, USDA Forest Service, Pacific Southwest Research Station; John de Goede, Jacquelyn Bjorkman, Allan Hollander, Ryan M. Boynton, James F. Quinn, James H. Thorne – University of California, Davis

ABSTRACT: Healthy urban forests can provide ecosystem functions and services that benefit humans such as energy conservation, carbon storage and air quality improvement. However, trees in cities face a plethora of threats that can reduce these benefits. The primary purpose of this study is to provide baseline data on the structure, function and value of urban forests in California communities as a basis for change detection. The structure of the urban forest in urban areas (e.g., tree density, basal area, species composition) was summarized for six land use categories in six California climate zones using tree data from field plots. The effects of city trees on air quality, building energy use, atmospheric carbon dioxide, rainfall interception and property values were calculated using plot data and numerical models. To scale-up results from the plot to the landscape, transfer functions (e.g., kWh of air conditioning energy saved annually per hectare urban tree canopy (UTC)) were calculated using UTC mapped at 1-m resolution. Although California’s UTC covered 15% of the urban area and was composed of 173.2 million trees, the UTC per capita was the lowest among U.S. states (90.8 m2). Quercus was the most abundant genera state-wide (22%) while Pinus had the highest basal area (10%). Overall, the tree population was youthful, with 50% of trees in the smallest diameter class. California’s urban forests provide $8.3 billion in annual ecosystem services and as a total asset are valued at $181 billion, which amounts to $2.52 in benefits returned for every dollar spent (assuming an average per tree management cost of $19). The risk of catastrophic tree loss is discussed using as an example the threat posed by Invasive Shot Hole Borer (Euwallacea sp.) currently infesting multiple tree species in Southern California.

Wednesday April 11, 2018 4:30pm - 4:45pm CDT
Spire Parlor