2015 Tree Inventory Results
SUBMITTED BY CARRIE BLACK, CS AIDE II
In summer 2015, PP&R Urban Forestry organized neighborhood stakeholders to conduct volunteer-led street tree inventories in Buckman, Centennial, Hazelwood, Irvington, King, Mill Park, Montavilla, Mt. Scott-Arleta, Mt. Tabor, North Tabor, Old Town-Chinatown, Parkrose, Parkrose Heights, Powellhurst Gilbert, Roseway, Sabin, Sumner, Vernon and Woodlawn neighborhoods. This year’s inventory covered nearly twice as many neighborhoods as 2014, and expanded farther east than ever before. More than 340 volunteers donated 3,500 hours to the project by identifying, measuring, and mapping over 52,000 trees. In addition to collecting data in the field, volunteers entered inventory data into ArcGIS at the Urban Forestry office.
Inventory results, recommendations, and maps were compiled into individual neighborhood reports. Reports are available at http://www.portlandoregon.gov/parks/article/433143. An interactive map is also available for searching the 157,000 trees in the database by address. Inventory highlights are listed below.
Composition: 152 different tree types were found, ranging from 28 in Old Town-Chinatown to 108 in Montavilla. Tree counts range from 990 – 6,200 trees per neighborhood. The most common trees across all neighborhoods are Norway maple, red maple, cherry, and plum. Deciduous broadleaf trees dominate the tree population, but evergreens are more common in neighborhoods farther to the east – evergreen conifers make up more than 10% of all trees in Sumner, Parkrose, Parkrose Heights, Hazelwood, Mill Park, Powellhurst-Gilbert, and Centennial.
Species diversity: Nearly all neighborhoods exceed the recommended guidelines for species diversity for at least their top genus and family. In Parkrose Heights, the most common family (Sapindaceae) has met but not exceeded the diversity threshold of 20%. Across all neighborhoods, maples are widely overrepresented at the species, genus, and family level. Cherry and plum are also overrepresented at the species and genus level, as is the rose family (Rosaceae) overall.
Size class distribution: Across this year’s neighborhoods, just under 50% of the population is comprised of trees under 6” DBH. However, over 60% of the population in Mt. Scott-Arleta and Centennial fall into this size class, while only about 21% of trees in Old Town-Chinatown are less than 6” DBH. Larger diameter size classes (>18” DBH) are less represented in a majority of neighborhoods, but this class comprises a greater portion of the population in Irvington (34%), Buckman (20%), Sumner (19%) and Parkrose (19%). The largest tree in Parkrose Heights, a 79” DBH European beech, is also the largest diameter street tree inventoried in Portland, to date.
Tree condition: 87-95% of trees are rated in good or fair condition in all neighborhoods, 4-11% rate poor, and 1-2% are dead.
Planting site type: While improved rights-of-way comprise the vast majority (77% or more) of planting site types in most neighborhoods, unimproved rights of-way are more common in neighborhoods to the east. Over 30% of all sites in Hazelwood, Powellhurst Gilbert, and Centennial are unimproved, and over 50% of sites in Parkrose, Mill Park, Parkrose Heights, and Sumner are unimproved.
Planting site size: Large disparities were found among neighborhoods. Small sites, which support small form trees, range from a low of 4% of sites in Roseway up to 73% of sites in King. Planting site size corresponds to the mature size of a tree that can be supported in the site.
Stocking levels: In residential neighborhoods, stocking levels range from 79% in Irvington to 35% in Parkrose Heights. Neighborhoods with more unimproved sites have lower stocking levels than those with more improved sites. Over 66% of all sites in Sumner are unimproved, while stocking level is only 36%. Mt. Scott Arleta and Mt. Tabor represent the median stocking level, with 54% of their planting sites stocked. Over 40,000 spaces have been identified for tree planting across all neighborhoods.
Undersized trees: More than half of large planting sites in all neighborhoods are stocked with undersized trees. This ranges from 90% of all large sites in Old Town-Chinatown to 56% in Powellhurst-Gilbert.
Annual benefits: Total annual environmental and aesthetic benefits provided by street trees range from $57,000 to $1,343,000 per neighborhood, annually.
Replacement values: Replacement values of the street tree population range from $2.3 - $35.9 million.
On November 7th, 2015, over 70 participants convened at the Tree Inventory Summit to discuss results and begin creating tree plans. After presentations on the data and hearing from guest speakers on species diversity, tree maintenance, canopy, and tree history, participants broke into neighborhood groups to draft tree plans. The tree plans include a vision statement, goals, action items, and recommendations for property owners. Urban Forestry AmeriCorps members Matthew Downs and Patrick Key are serving as the Tree Plan Coordinators. They will work with each neighborhood tree team to plan two stewardship events between now and June 2016 to help groups stay organized and help meet tree plan goals. At the summit, Matthew and Patrick presented a menu of stewardship workshop options for participants to choose from, including planting, pruning, and maintenance events.
CONCLUSIONS AND FUTURE DIRECTION
Urban Forestry staff will continue to work with tree teams to provide tree plan guidance and ongoing support. Next year’s inventory will be the last, as Urban Forestry staff and volunteers work to complete the remaining neighborhoods on the east side of the City. Applications for 2016 inventories are available on the project website and are due January 15. For more information about the Tree Inventory Project and to download presentations and data, visit: www.portlandoregon.gov/parks/treeinventory.
Volunteers gather for a Roseway inventory work day.
Top: An inventory volunteer measures the DBH of a street tree in the Powellhurst-Gilbert neighborhood (left); Neighborhood Tree Teams work on their Tree Plans at the summit at Mt Scott Community Center in November (right).