Street Tree Inventory Report Concordia Neighborhood

Transcription

1 Street Tree Inventory Report Concordia Neighborhood January 2011

2 Street Tree Inventory Report: Concordia Neighborhood January 2011 Compiled by: Angie DiSalvo, Portland Parks & Recreation Urban Forestry , Consulting Arborists Myles Black, Portland Parks & Recreation Urban Forestry Charley Davis, Portland Parks & Recreation Urban Forestry Karl Dawson, Portland Parks & Recreation City Nature Rick Faber, Asplundh Tree Expert Co. Joe Hintz, Portland Parks & Recreation Urban Forestry Autumn Montegna, Portland Parks & Recreation City Nature Concordia Tree Team Jim Gersbach, Dove Hotz, Kristin Kaye, Larry Light, Bob Pallesen, Rebecca Wetherby, Barbara Wharton GIS Data Entry Phil Clark, Danielle Fuchs, Jackie Gruber GIS Technical Support Josh Darling, Portland Parks & Recreation itree Calculation Zach Gustafson, Garrett Phillips, Mark Savage Stocking Level Data Bureau of Environmental Services Financial Support Portland Parks & Recreation and East Multnomah Soil and Water Conservation District Special thanks are due to the many additional volunteers who contributed time and effort to inventory Concordia s street trees. Portland Parks & Recreation 1120 SW Fifth Avenue, Suite 1302 Portland, Oregon (503) 823-PLAY Commissioner Nick Fish Director Zari Santner

3 Table of Contents Project Background Neighborhood Characteristics... 2 Tree Distribution Tree type distribution... 3 Tree family distribution Species diversity Functional tree type and mature tree size distribution... 4 Tree Size Distribution Tree size (relative tree age)... 6 Tree Condition... 6 Stocking Level... 7 Right tree in the right place... 8 Replacement Values Aesthetic and Environmental Benefits... 9 Recommendations References... 13

4 Volunteers guided by PP&R Urban Forestry staff collected data on all 4,636 street trees within Concordia neighborhood to compile the first complete neighborhood street tree inventory. Data will be used to inform the creation of a Neighborhood Stewardship Plan to guide volunteers in caring for their community s trees.

5 Project Overview Project Background This report provides results of a street tree inventory conducted in Concordia neighborhood in 2010, along with Portland Parks & Recreation Urban Forestry staff recommendations to improve the condition of the urban forest. Street trees were inventoried in Concordia in summer and fall 2010 by trained volunteers and PP&R Urban Forestry staff. Over the course of three monthly workshops, 50 volunteers contributed 250 hours collecting data on 4,636 trees. Trees at every tax lot in the neighborhood were inventoried; data collected included tree type (species or genus), condition, size (diameter at breast height), planting strip width, and presence of overhead high voltage lines. Data was supplemented with available planting space data collected by the Bureau of Environmental Services in 2009 and Volunteers experienced and trained in tree identification acted as team leaders, and data were collected in pairs on paper forms. Questions regarding species or site identification were answered by certified arborists during data collection. Staff conducted spot checks on data to verify accuracy. Data were later digitized and entered by volunteers into an ArcGIS geodatabase. The Concordia Tree Team, a subcommittee of the Concordia Neighborhood Association, was essential to organizing workshops, recruiting volunteers, and promoting the project within the community. Additional volunteer support came from Neighborhood Tree Stewards, a group of volunteers trained by PP&R Urban Forestry on tree issues. The majority of data analysis and recommendations were completed by PP&R Urban Forestry staff. The itree benefits analysis was completed by Portland State University students Zach Gustafson, Garrett Phillips, and Mark Savage. Funding for this project was provided by Portland Parks & Recreation Urban Forestry and an East Multnomah Soil and Water Conservation District Partners in Conservation grant. Data from the inventory are available to the public in spreadsheet or ArcGIS format by contacting PP&R Urban Forestry. Portland Parks & Recreation 1

6 Neighborhood Characteristics Concordia neighborhood is located in northeast Portland (Figure 1). Its borders are NE 22nd Avenue to the west, NE Columbia Boulevard to the north, NE 42nd Avenue to the east, and NE Prescott Street and NE Alberta Court to the south. Neighborhood landmarks include the Alberta Arts District, Concordia University, and Kennedy Community Garden. Key neighborhood tree assets include the Ainsworth Linear Arboretum, Fernhill Park, and Meek School Learning Landscape. Concordia is located in the Columbia Slough watershed. Figure 1: Location of Concordia neighborhood in Portland The neighborhood is characterized by a diverse population and has undergone rapid changes in the past ten years. According to the 2000 Census (Table 1), 71% of homes are owner-occupied and the median income is near $26,000/year, with 19% percent of residents living below the poverty level. Table 1: Neighborhood and citywide demographics Demographics (2000 Census) Concordia Portland Area 849 acres 89,651 acres Population 9, ,750 Density 11 persons/acre 6 persons/acre Demographics 55% white; 45% non-white 72% white; 28% non-white % of properties occupied by homeowners 71% 56% Median income $25,694 $43,958 % below poverty level 19% 11% 2 Street Tree Inventory Report Concordia Neighborhood 2011

7 Tree Distribution TREE TYPE distribution Concordia s public rights-of-way host a diverse array of tree types (trees identified to the species or genus level). The street tree population consists of 4,636 trees of 82 types (Table 2). Fifteen tree types comprise nearly 80% of the resource, leaving the remaining types to represent 1% or less of the resource each. Maples are the most common tree type, representing 23% of all street trees. Of the maples, Norway maple comprised 4.4% of total street trees and other maples comprised 18.6%. Table 2: Distribution of the 15 most abundant street tree types in Concordia Common Species Number % of Mean Name of Trees Total DBH maple Acer spp. 1, % 8.3 cherry Prunus spp % 9.7 dogwood Cornus spp % 5.8 crabapple Malus spp % 5.1 ash Fraxinus spp % 7.5 plum Prunus spp % 8.8 birch Betula spp % 14.3 pear Pyrus spp % 7.0 hawthorn Craetagus spp % 7.4 oak Quercus spp % 9.1 snowbell Styrax spp % 2.4 sweetgum Liquidambar styraciflua % 15.4 linden Tilia spp % 8.3 magnolia Magnolia spp % 3.3 zelkova Zelkova serrata % 2.7 Thirty-seven families are represented in the neighborhood, and the fifteen most abundant families comprise nearly 90% of the resource. Rosaceae (rose) and Aceraceae (maple) are the most commonly found and represent 28.4% and 23% of trees, respectively (Table 3). Other important families include Cornaceae (dogwood) with 8%, Oleaceae (olive) with 6.2%, Betulaceae (birch) with 5.3%, and Fagaceae (beech) with 3.0%. Portland Parks & Recreation 3

8 Table 3: Distribution of the 15 most abundant tree families in Concordia Family Family Tree Types Included Number of % of Rosaceae Common Name in the Family Trees Total Trees rose apple, cherry, crabapple, hawthorn, mountain ash, peach, pear, plum 1, % Aceraceae maple box elder, maple 1, % Cornaceae dogwood dogwood, dove tree, tupelo % Oleaceae olive ash, lilac tree, olive % Betulaceae birch alder, birch, hazelnut, hophornbeam, hornbeam % Fagaceae beech beech, chestnut, oak % Fabaceae legume amur maackia, golden chain tree, Kentucky coffeetree, locust, mimosa tree, pagoda tree, redbud, yellowwood % Ulmaceae elm elm, hackberry, zelkova % Pinaceae pine cedar, Douglas fir, fir, pine, spruce % Styracaceae storax snowbell % Altingiaceae sweetgum sweetgum % Malvaceae mallow linden % Magnoliaceae magnolia magnolia, tulip poplar % Juglandaceae walnut walnut % Cupressaceae cypress arborvitae, cypress, juniper, redwood, western redcedar % Species Diversity A general rule of thumb for urban forest species diversity is the rule. No species should represent more than 10% of the total, no genus should represent more than 20% of the total, and no family should represent more than 30% of the total. Concordia s trees meet these criteria, and as such, the resource distribution is reasonably diverse. Functional tree type and mature tree size distribution Broadleaf deciduous trees dominate the landscape, accounting for 96% of all street trees (Table 4). Broadleaf evergreen trees comprise 1% and coniferous evergreen trees comprise 3% of the total. Tree size designation (small, medium, and large) is determined by the mature size of the tree. Medium-sized trees account for 48% of the resource and small-sized trees account for 38%, while large trees only 4 Street Tree Inventory Report Concordia Neighborhood 2011

9 account for 14% (Table 4). Compared to citywide averages, far fewer large form trees are planted in Concordia (14% vs. 37%). Table 4: Distribution of trees by functional tree type and mature tree size Functional Tree Type Small Medium Large Total Broadleaf deciduous 37% 47% 12% 96% Broadleaf evergreen 0% 1% <1% 1% Coniferous evergreen <1% <1% 2% 3% Palm evergreen <1% 0% 0% 0% Total 38% 48% 14% 100% Tree Size Distribution Tree Size (Relative Tree Age) The relative ages of trees may be approximated using size measured by diameter at breast height (DBH). Generally, trees increase in size with age, along with the value of the tree and the magnitude of the benefits that the tree provides. Trees were categorized into diameter classes to show the proportion of trees at various stages of maturity. Note that an uneven-aged population is desirable for managing tree maintenance costs over time. Age diversity ensures that canopy coverage and community complexity are not reduced with mortality. Concordia s streets host a wide range of tree sizes from the youngest half-inch sapling to the largest, a 69 DBH bigleaf maple. Over half of all trees are less than 6 DBH, and less than 4% are larger than 24 DBH (Figure 2). Figure 2: Relative tree age (tree size by diameter class) 35% 30% Percent of Trees 25% 20% 15% 10% 5% 0% >42 Diameter Class (inches) Tree size distribution is heavily skewed towards smaller (younger) trees, and compared to citywide averages, Concordia has similar percentages of younger, smaller trees but fewer larger, older trees. Tree size distributions are similar regardless of whether or not planting strips are located under high voltage Portland Parks & Recreation 5

10 power lines (Figure 3). Divided into functional size classes, Concordia s small and medium form trees dominate all diameter classes under 24 DBH (Figure 4). Figure 3: Relative tree age (tree size by diameter class) of trees in planting strips under high voltage wires and without high voltage wires Percent of Trees 18% 16% 14% 12% 10% 8% 6% 4% 2% 0% >42 Diameter Class (inches) under wires without wires Figure 4: Relative tree age (tree size by diameter class) of trees by functional size class Percentage of Trees 16% 14% 12% 10% 8% 6% 4% 2% 0% Diameter Class (inches) Small medium large Tree Condition Tree condition was assessed by assigning trees to one of four categories: good, fair, poor, and dead. 56% of trees rated good, 33% rated fair, 10% poor, and 1% dead (Table 5). Table 5: Trees by condition class Condition % of Total Trees Good 56.3% Fair 33% Poor 10.2% Dead 0.5% 6 Street Tree Inventory Report Concordia Neighborhood 2011

11 Of the most commonly found tree types, the healthiest trees were sweetgum, linden, ash, and zelkova (Table 6). In poorest condition were hawthorn, birch, plum, and cherry. Table 6: Condition class percentages and numbers of trees for the 15 most abundant tree types Common Species % of Total Trees (Number of Trees) Name Good Fair Poor Dead ash Fraxinus spp. 59.4% (158) 35.3% (94) 5.3% (14) 0.0% (3) birch Betula spp. 34.5% (69) 42.0% (84) 22.5% (45) 1.0% (2) cherry Prunus spp. 41.5% (180) 41.7% (181) 16.4% (71) 0.5% (4) crabapple Malus spp. 51.0% (152) 39.9% (119) 9.1% (27) 0.0% (0) dogwood Cornus spp. 40.7% (142) 47.9% (167) 10.3% (36) 1.1% (3) hawthorn Craetagus spp. 42.2% (68) 23.0% (37) 34.8% (56) 0.0% (0) linden Tilia spp. 55.0% (44) 43.8% (35) 1.3% (1) 0.0% (0) magnolia Magnolia spp. 67.2% (41) 24.6% (15) 8.2% (5) 0.0% (0) maple Acer spp. 70.7% (755) 23.3% (249) 5.7% (61) 0.3% (2) oak Quercus spp. 65.3% (62) 26.3% (25) 8.4% (8) 0.0% (1) pear Pyrus spp. 58.5% (103) 35.8% (63) 5.7% (10) 0.0% (0) plum Prunus spp. 33.3% (69) 44.4% (92) 21.7% (45) 0.5% (1) snowbell Styrax spp. 57.8% (52) 32.2% (29) 10.0% (9) 0.0% (0) sweetgum Liquidambar sytraciflua 84.0% (68) 16.0% (13) 0.0% (0) 0.0% (0) zelkova Zelkova serrata 81.5% (44) 13.0% (7) 5.6% (3) 0.0% (0) Stocking Level stocking level Street tree stocking level reflects the percentage of potential planting spaces that are currently occupied by trees. Citywide, stocking levels range from 37% in southeast Portland to 64% in northwest Portland, with a 45% average. Concordia s stocking level for residential areas is 56%, higher than the citywide average and northeast neighborhood average (41%) (Table 7). Stocking level data in Table 7 was provided by the Bureau of Environmental Services. Table 7: Stocking level data for single-family residential lots Planting Strip Available Existing Total Stocking Code and Description Planting Spaces Trees Spaces Level A with or without wires % B 3-4 with or without wires % C without wires % D with wires % E 6-8 without wires % F >6 with wires ,488 66% G >8.5 without wires ,434 62% Totals ,204 1,434 56% Portland Parks & Recreation 7

12 Planting space availability is subject to a number of guidelines, including width of the planting strip, presence/absence of high voltage power lines, and distance from conflicts (property lines, stop signs, etc). In single-family residential lots, 3,241 empty spaces have been identified for tree planting in residential areas in Concordia. Planting spaces are categorized into planting strip categories based upon width and overhead wire presence. Higher stocking levels are found in larger planting strips, and planting strips larger than six feet in width are at least 62% stocked. Right tree in the right place Tree placement is vital for maximizing the benefits trees provide and minimizing avoidable costs. The right tree in the right place will experience fewer obstacles to reaching maturing and is easier to maintain. A large-maturing tree in an undersized space will be increasingly stressed as it ages, and will come into conflict with infrastructure. A small-growing tree in a large planting strip represents a missed opportunity, as it will not live as long or grow as large as a larger growing tree. Table 8: Number and percentage of trees growing in correct size, undersized, and oversized rights-of-way by planting strip code Planting Strip Trees are the Trees are undersized Trees are oversized Code and Description correct size for strip for the planting strip for the planting strip A with or without wires 44% (172) 56% (218) B 3-4 with or without wires 46% (213) 10% (48) 44% (206) C without wires 54% (157) 24% (70) 22% (63) D with wires 33% (109) 9% (28) 58% (189) E 6-8 without wires 46% (168) 46% (169) 9% (32) F >6 with wires 35% (348) 25% (248) 40% (401) G >8.5 without wires 36% (318) 64% (565) Totals 40% (1,485) 30% (1,128) 30% (1,110) 40% of Concordia s street trees are growing in planting strips that are appropriately sized for their growth form (Table 8). 30% of trees are growing in undersized planting strips and 30% are growing in oversized planting strips. Maples and unknown species were removed from this analysis, as data collected made it difficult to determine with accuracy what an appropriate sized strip is for these categories. Large planting strips without overhead power lines provide the best opportunity for expanding canopy and providing benefits from trees. 46% of trees in planting strips 6-8 wide without wires and 64% of trees in planting strips over 8 wide without wires are undersized. The most commonly planted small trees that appeared in these large strips were dogwood and cherry, which were 17% and 11% of the undersized trees. Replacement Values Replacement values of trees were calculated by itree Streets as estimates of the full cost of replacing trees in their current condition, should they be removed for some reason. Species ratings, replacement costs, and basic prices were obtained for each species in each reference city from regional appraisal guides. The replacement cost of Concordia s tree population is valued at $9,763,518. The most valuable size classes of trees are those between 6 DBH and 30 DBH (Figure 5). Replacement values were the 8 Street Tree Inventory Report Concordia Neighborhood 2011

13 highest for maple ($1,684,580), cherry ($901,288), Norway maple ($871,131), and birch ($685,938). Figure 5: Replacement values of trees by diameter class (inches) $2,500,000 Replacement Value $2,000,000 $1,500,000 $1,000,000 $500,000 $ >42 DBH Class (inches) Aesthetic and Environmental Benefits Using itree Streets, Concordia s street tree population was assessed to quantify the dollar value of annual environmental and aesthetic benefits provided by trees: energy conservation, air quality improvement, carbon dioxide reduction, stormwater control, and property value increase. The model relies on tree size and species, as well as current pricing for electricity rates, median home resale value, regional stormwater interception costs, and costs of tree maintenance. Concordia s street trees provide over $314,000 annually in aesthetic and environmental benefits, as calculated by itree Streets (Table 9). Annual benefits are valued by category at over $14,000 in residential energy savings, nearly $3,000 in carbon sequestration, nearly $5,000 in air quality improvement, nearly $57,000 in storm water management, and over $234,000 in aesthetic and other benefits. Each tree provides an average of $67 worth of benefits annually. Table 9: Valuation of the environmental and aesthetic benefits provided annually by Concordia s trees Benefits Total ($) $ / Tree Energy savings $14,726 $3.17 Carbon sequestration $2,992 $0.65 Air quality improvement $4,822 $1.04 Stormwater processing $56,964 $12.22 Aesthetics $234,964 $50 Total benefits $314,468 $67.08 Of the most common tree types, oak, Norway maple, walnut, and sweetgum provided the highest annual per tree benefits, at least double the $67 average (Table 10). Snowbell, crabapple, dogwood, zelkova, and hawthorn trees provided the least amount of benefits at half or less of the average. Benefit analysis is a function of tree size (DBH) and species characteristics. Portland Parks & Recreation 9

14 Table 10: Average annual environmental and aesthetic benefits provided by Concordia s most abundant street tree types Tree Type Energy CO2 Air Storm Aesthetic/ Total ($) Quality water Other per tree oak $5.67 $0.90 $1.82 $23.62 $ $ maple, Norway $6.81 $1.06 $2.24 $29.15 $ $ walnut $7.19 $1.27 $2.32 $29.91 $95.35 $ sweetgum $8.06 $1.13 $1.86 $33.88 $88.25 $ birch $6.00 $0.48 $1.98 $25.75 $62.25 $96.46 maple $3.68 $0.43 $1.17 $12.94 $65.21 $83.43 ash $2.44 $0.53 $0.95 $11.00 $68.38 $83.30 linden $3.29 $0.65 $1.05 $12.18 $64.73 $81.90 cherry $2.82 $1.39 $0.99 $8.08 $39.87 $53.15 pear $3.35 $0.47 $1.33 $13.43 $33.04 $51.62 plum $2.36 $1.05 $0.82 $6.44 $34.35 $45.02 hawthorn $1.97 $0.82 $0.68 $5.19 $28.75 $37.41 zelkova $0.55 $0.07 $0.13 $1.99 $24.87 $27.61 dogwood $1.42 $0.55 $0.48 $3.61 $21.47 $27.53 crabapple $1.18 $0.45 $0.40 $2.96 $18.72 $23.71 snowbell $0.29 $0.07 $0.09 $0.60 $5.74 $ Street Tree Inventory Report Concordia Neighborhood 2011

15 Recommendations Based on tree inventory data presented in this report, PP&R Urban Forestry staff make the following recommendations. Planting While Concordia s current 56% stocking level exceeds the City s average, there is ample room to plant more trees with 3,241 sites identified. Plantings should continue to include a diverse array of species, genera, and families, particularly those other than maple (Acer), cherry (Prunus), dogwood (Cornus), and in the Rosaceae family. Planting opportunities should be prioritized to plant large-form trees in wide planting strips without overhead wires. Planting in the smallest planting strips is not a priority, as they are more difficult to manage and provide very little return on investment. However, all plantings help contribute to a neighborhood tree ethic and encourage others to plant. Take advantage of existing planting programs, such as low cost trees through Friends of Trees. These plantings are currently funded through the City for the next few years; afterwards cost and availability may change. Young Tree Establishment and Maintenance With over 50% of trees being 6 DBH or less, special attention should be paid to properly water and establish young trees. Young trees should be structurally pruned to promote proper form as street trees. This is critical in the first ten years after planting. Educate property owners on how to properly care for trees (pruning, watering, root barriers) in order to reduce and delay future problems and conflicts with infrastructure. Mature Tree Maintenance With less than 25% of trees being larger than 12 DBH, and very few over 24 DBH, special care should be taken to maintain and care for larger trees. Trees provide the most benefits as they reach maturity, and without early maintenance, tree care is the most expensive for large trees. Increasing the level of maintenance of large, old trees will maximize the ecosystem services provided by these high value members of the urban forest. Seek funding or assistance for low-income property owners to care Portland Parks & Recreation 11

16 for mature trees. Retain existing large trees. Benefits and time are lost when older trees are removed and replaced with smaller and younger tree species. Promote the importance and benefits of large-form species and mature trees within the community. Nominate trees for Portland s Heritage Tree Program to promote interest in trees and appreciation for mature and diverse specimens. Removals Encourage removal and replacement of dead trees and trees in poor condition. Encourage replacement of underperforming species, including undersized trees in large rights-ofway, with higher functioning, appropriately sized trees. 12 Street Tree Inventory Report Concordia Neighborhood 2011

17 References City of Portland Office of Neighborhood Involvement and US Census Bureau Portland Neighborhood Demographic Data. Portland Parks & Recreation Portland s Urban Forest Canopy: Assessment and Public Tree Evaluation. US Forest Service. itree Streets (version 3.1). Portland Parks & Recreation 13