Street Tree Inventory Report Grant Park Neighborhood October 2016 Street Tree Inventory Report: Grant Park Neighborhood October 2016
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Street Tree Inventory Report Grant Park Neighborhood October 2016 Street Tree Inventory Report: Grant Park Neighborhood October 2016 Written by: Kat Davidson, Angie DiSalvo, Julie Fukuda, Jim Gersbach, Jeremy Grotbo, and Jeff Ramsey Portland Parks & Recreation Urban Forestry 503-823-4484 [email protected] http://portlandoregon.gov/parks/treeinventory Grant Park Tree Inventory Organizers: Liz Hay Staff Neighborhood Coordinator: Jim Gersbach Data Collection Volunteers: Linda Brannan, Doug Brazil, Neff Breen, Rick Burkard, Patrick Burns, Dianna Choi, Catherine Clark, Don Crossley, Ann DeNies, Mary Desch, Russell Eng, Gregg Everhart, Claudia Fabbrini, Karla Fitzwater, Liz Hay, Leo Helm, Pamela Hickman, Lisa Horowitz, Martha Irvine, Kiel Jenkins, Ben Jones, James Keiter, Bill Kownacki, Fred Kratz, Marc Langhammer, Kate Laudermilk, Ariel Lewin, Louis Miles, Melinda Moeur, Shelley Morrison, Tamara Olcott, Larry Rabinowitz, Bruce Richard, Kyna Rubin, Amy Simpson, Matt Vellella, Aaron Wolf, and Samantha Wolf Data Entry Volunteers: Max Blasdel, Michael Brehm, Dylan Eglin, Tiffany Eurich, Spencer Keller, Matthew Pryzborski, Nathan Riggsby, Takayuki Shigematsu, Joshua Sindel, Rebecca Tait, and Shauna Volk Arborist-on-Call Volunteers: Van Bogner, Casey Clapp, and Fred Nilsen GIS Technical Support: Josh Darling, Portland Parks & Recreation Financial Support: Portland Parks & Recreation Cover Photos (from top left to bottom right): 1) Unusual burgundy seeds on a Euptelea pleiosperma, an extremely rare find in Portland. 2) The changing leaves of a Persian ironwood (Parrotia persica). 3) A pair of katsuras (Cercidiphyllum japonicum) beginning to show fall color. 4) Chains of seeds forming on a sourwood (Oxydendrum arboreum). 5) The fruit of a dove tree (Davidia involucrata). 6) Flaking bark on a mature redbud (Cercis canadensis). 7) The vibrant flowers of a Pecos crape myrtle Lagerstroemia( indica x fauriei 'Pecos'). 8) Colorful margins on the leaf of a tricolor beech (Fagus sylvatica 'Roseomarginata'). ver. 10/18/2016 Portland Parks & Recreation 1120 SW Fifth Avenue, Suite 1302 Portland, Oregon 97204 (503) 823-PLAY Commissioner Amanda Fritz www.PortlandParks.org Director Mike Abbaté Contents Key Findings .......................................... 1 About Portland’s Street Tree Inventory ..................... 3 Grant Park Street Tree Inventory ......................... 5 Neighborhood Characteristics ......................... 5 Urban Forest Composition............................ 6 Species diversity and tree type composition ........... 6 Functional tree type .............................. 8 Size class distribution ............................. 9 Mature tree form distribution ..................... 10 Importance value................................ 11 Tree Condition .................................... 11 Planting Site Composition and Stocking Level ........... 13 Planting sites................................... 13 Stocking level .................................. 13 Right tree in the right place ....................... 14 Replacement Value ................................. 15 Environmental and Aesthetic Benefits .................. 16 The Future Forest of Grant Park ...................... 17 Recommendations ..................................... 21 Next Steps: Tree Plans and Tree Teams .................... 23 References ........................................... 25 Appendices........................................... 27 A: Methods ....................................... 27 B: Street trees of Grant Park by tree type ............... 29 C: Street trees of Grant Park by size (map) .............. 32 D: Vulnerability to key pests (map)..................... 33 E: Young street trees (trees ≤ 3” DBH) (map)............. 34 F: Large street trees (trees > 24” DBH) (map) ............ 35 G: Poor and dead street trees (map) .................... 36 H: Planting site types (map) .......................... 37 I: Planting site sizes (map)............................ 38 J: Available street tree planting sites (map) ............... 39 K: Priority street tree planting sites (map) ............... 40 Portland Parks & Recreation i Volunteers, guided by Portland Parks & Recreation Urban Forestry staff, collected data on all 2,787 street trees within Grant Park neighborhood to compile the neighborhood’s first complete street tree inventory. The data are being used to inform the creation of a Neighborhood Tree Plan to guide volunteers in caring for their community’s trees. ii Street Tree Inventory Report – Grant Park Neighborhood 2016 Key Findings This report provides the results of a street tree inventory conducted in the Grant Park neighborhood in 2016, along with Portland Parks & Recreation (PP&R) Urban Forestry staff recommendations for the Grant Park tree team. Over the course of four work days, 38 volunteers contributed more than 156 hours collecting data on each of the neighborhood’s 2,787 street trees. URBAN FOREST STRUCTURE • Grant Park’s street tree population is dominated by maple, cherry, dogwood, and pear and does not meet recommended species diversity guidelines. While 87 tree types were found in this inventory, only two families, Sapindaceae and Rosaceae, account for half (51.3%) of the street tree resource. Furthermore, both the Acer (maple) and Prunus (plum, cherry) genera are over represented, leaving Grant Park’s street tree population vulnerable to pests, pathogens, and the various effects of a changing climate. • The dominance of broadleaf deciduous trees (98%) in Grant Park points to a need to plant more evergreen trees for year-round benefits and to create a more resilient urban forest. • Only 16.3% of trees in Grant Park are young (<3” DBH), leaving few trees to offset mortality as the population ages. Frequent planting of young trees helps to ensure a stable street tree population with a healthier age distribution in the future. • Only 17% of Grant Park’s street trees are large form varieties. Large form trees are necessary to increase canopy cover and the benefits it provides for Grant Park’s residents. Planting the estimated 151 large available spaces identified in this inventory will maximize tree canopy in the Grant Park neighborhood's rights-of-way. TREE CONDITION • The majority of trees inventoried in Grant Park are in fair or good condition. The genus with the highest percent of trees in poor condition is Betula (birch), 30.8% of which are rated poor, followed by Prunus, at 26.6%. Of all street trees rated poor, two out of every five (39.8%) are in the Rosaceae family. PLANTING SITES AND STOCKING LEVEL • Although 78% of street tree planting sites in Grant Park have trees, there are 666 sites that are empty and ready for planting. • Only 28.6% of Grant Park’s large planting sites contain trees large enough for the site. While large sites make up 39% of all sites where trees are found, only 17% of Grant Park’s street trees are large form trees. Small form trees planted in large planting sites are a missed opportunity because larger trees contribute many times more benefits than do smaller ones. URBAN FOREST VALUE AND BENEFITS • Grant Park’s street trees produce an estimated $572,565 annually in environmental and aesthetic benefits. The replacement value of this resource is $13.5 million. Planting efforts focused on appropriately sized trees distributed across the neighborhood will ensure that future benefits are equitably distributed among all residents. Portland Parks & Recreation 1 Clockwise from top left: 1) Evergreen conifers like this attractive lacebark pine (Pinus bungeana), are under represented in Grant Park, making up only 1% of all street trees. 2) These large form bur oaks (Quercus macrocarpa) are appropriate for this wide strip and will provide many times more benefits than if a small form tree had been planted here. 3) At 60.9" DBH, this elm (Ulmus sp.) is the largest diameter street tree in Grant Park. 4) Bumping out sidewalks to make room for tree roots is an alternative to removal of larger trees in constricted spaces, and will help support healthier tree growth. 2 Street Tree Inventory Report – Grant Park Neighborhood 2016 About Portland’s Street Tree Inventory THE IMPORTANCE OF STREET TREES Street trees are an important public asset in urban environments, serving as a buffer between our transportation corridors and our homes while enhancing the livability of our city. As integral components of a community’s green infrastructure, street trees provide multiple economic, environmental, and social benefits such as cleaner air and water, cooler summer temperatures, safer streets, and increased property values. Unlike traditional, “grey” infrastructure, which begins to deteriorate the moment it is installed, the benefits that street trees provide increase over the lifetime of the tree, making their planting and maintenance one of the best investments a city and its residents can make. While street trees are only one component of Portland’s urban forest, they are particularly important because they are the trees that residents Urban forests are complex, living interact with most. Having adequate information resources that interact both about the street tree population allows a community to make informed decisions about species selection, positively and negatively with the planting, and maintenance priorities. Information on surrounding environment. They the location, condition, and diversity of the street tree produce multiple benefits and have population enables our communities to steward this resource and