City Trees

January/February 2017

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Page 38 of 39 39 Database Captures Urban Tree Sizes, Growth Rates across United States The U.S. Forest Service's Pacific Southwest Research Station recently published a technical manual and launched the most extensive database available cataloging urban trees with their projected growth tai- lored to specific geographic regions. "Knowing a tree's maximum size can avoid future con- flicts between roots and sidewalks or branches and power lines," said Greg McPherson, research forester for the Forest Service and lead author of the technical report and database. The products are a culmination of 14 years of work, ana- lyzing more than 14,000 trees across the United States. Whereas prior growth models typically featured only a few species specific to a given city or region, the newly released database features 171 distinct species across 16 U.S. climate zones. The trees studied also spanned a range of ages with data collected from a consistent set of measurements. "There are very few studies, if any, in the world that can compare to this in terms of scope with regard to the number of trees studied, the species analyzed, the geo- graphic range and ages, and so forth," McPherson said. Advances in statistical modeling also have given the projected growth dimensions a level of accuracy never before seen. Moving beyond just calculating a tree's diameter or age to determine expected growth, the research incorporates 365 sets of equations to project growth. "Although tree growth is the result of complex process- es, growth equations capture changes in tree size with age in a surprisingly simple and accurate way," said Natalie Van Doorn, a research urban ecologist with the Forest Service and co-author on the study. In addition to predicted tree growth, the manual provides species-specific data on foliar biomass, or amount of foliage, that is critical to projecting uptake of air pollutants. Written in a way to be accessible to non-technical users, the technical report gives step-by-step instructions on how to use the equations to calculate tree dimensions, biomass, carbon storage and other features of interest to urban foresters. "The research and publication were done with the urban forester and city planner in mind," Van Doorn said. "Urban trees benefit communities in innumerable ways, and it's this information can help communities make the most of these natural resources." SMA News 2017 Internship Program SMA members may apply to host a sum- mer intern for ten weeks or—new this year—they may apply for an intern to help with a specific proj- ect, with the hours to be determined by the project needs. Also new this year, SMA members may recruit a student intern from a local edu- cational institution. Read more to learn the details, download our 2017 internship flyer, and complete an online application at Oct 15-20, 2017 – Details to come at 2013 SMA Interns Save the Date: The First-Ever MFI Canada! Cornwall, Ontario

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