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Urban Forest DiversityDefinition and Determination
Joe R. McBrideDepartment of Landscape Architecture and Environmental Planning
University of CaliforniaBerkeley, CA
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Objectives1. Define urban forest diversty2. Describe measurement of species composition in urban forests 3. Identify factors contributing to urban forest species diversity 4. Identify trends in species diversity5. Discuss the potential consequences of these trends6. Review recommendations for establishment and maintenance
of urban forest diversity
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Urban Forest Diversity
“The complexity of tree species composition, the size distribution of trees, and the patterns of distribution of trees within an urban forest”
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Importance of Diversity
1. In natural ecosystems there is a relationship between stability and diversity
2. Maintaining more diverse urban forests promotes greater stability
3. Diversity adds to functional and aesthetic values of urban forests
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Measures of Species Composition1. Species Richness2. Species Abundance3. Species Diversity
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Number of species in an area
Species Richness
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City RichnessSouth Lake Tahoe 35Menlo Park 145Santa Barbara 1,226
Tree Species Richnessin Three California Cities
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Species AbundanceRelative numbers of individuals of species
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Abundance of Street Trees in Berkeley
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Species Diversity
Measure of species richness and abundance
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Species Richness
D
C
B
A
Urban Forest #2Urban Forest #1Species
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Species Abundance
1580D
15125C
1590B
380100A
Urban Forest #2Urban Forest #1Species
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Simpson’s Diversity Index
D = 1 D = diversity index(pi)2 pi = proportion
of individuals inthe populationbelonging to
species i
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Forest ___ ___ ___ ___ Simpson’s Index1 0.50 0.50 0 0 2.002 0.425 0.25 0.20 0.125 2.983 0.25 0.25 0.25 0.25 4.00
Proportion of Population Represented by Species (pi)
Simpson’s Divesity Indicies of Hypothetical Urban Forests 3
Urban Forest #1 Urban Forest #2 Urban Forest #3
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City Simpson’s Diversity IndexMt. Vernon, Ohio 2.1Newark, New jersey 2.3Austin, Minnesota 2.7Perrysburg, Ohio 3.0Eugene, Oregon 3.3Los Angeles, California 3.9
Comparison of Urban Forest Diversity
From: McPherson and Rowntree, 1989
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Factors contributing to the variationin Urban Forest Species Diversity
1. Climate 2. Tree Species Richness of Local Biome3. History4. Expert Advise5. Spiritual/Psychological Values6. Availability of Planting Stock7. Epidemics of Insects and Disease8. Public Popularity
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Climate and Urban Forest DiveristySpecies Richness Analysis
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Koppen’s Climate Classification
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From: FAO - SDRN - Agrometeorology Group - 1997
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Cities Surveyed in each Climate ZoneTropical Moist Moist, Mid-latitude, Mild WintersBangkok BeijingLagos MoscowNew Delhi StockholmRio de Janeiro TokyoSingapore
Dry Climates PolarCario MurmanskDubai NuukLhasa ReykjavikPhoenix
Moist, Mid-latitude, Mild WintersAthens New YorkBrasilia ParisBuenos Aires QuitoCusco SeattleHong Kong SydneyJacksonville Tel AvivLondon VancouverLos Angeles
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Moscow - Distribution of Samples
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Urban Forest Surveys
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Street Data Form
Cross-section Sketch
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Climate and Species Richness
9MurmanskPolar
32MoscowMoist, Mid-latitudewith cold winters
48New YorkMoist, Mid-latitudewith mild winters
28CairoDry
37SingaporeTropical Moist
Average Species Richness
Example CityKoppen Climate
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Urban Forest Species Richness in Relation to Climate
A B C D EKoppen Climate
50 A = Tropical Moist Climates• B = Dry Climates
C = Moist, Mid-latitude Climateswith mild winters
40 D = Moist, Mid-latitude Climateswith cold winters
• E = Polar Climates•
30
•
20
10•
¨
¨
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Frost Hardiness Zones
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Urban Forest Species Richness in Relation to Hardiness Zones
30Dubai60 to 8013 - 14
46Cairo40 to 6011 - 12
42Athens20 to 409 - 10
42Paris0 to 207 - 8
32Moscow-20 to 05 - 6
9Murmansk-40 to -203 - 4
Average Species Richness
Example CityTemperature Range (oF)
Hardiness Zone
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Urban Forest Species Richness in Relation to Hardiness Zones
3-4 5-6 7-8 9-10 11-12 13-14Hardiness Zone
50 3-4 = -40 to -20o F• 5-6 = -20 to 0
7-8 = 0 to 20• • 9-10 = 20 to 40
40 11-12 = 40 to 6013-14 = 60 to 80
•30 •
20
10•
¨
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Factors contributing to the variationin Urban Forest Speices Diversity
1. Climate 2. Tree species richness of local biome3. History2. Spiritual/Psychological Values4. Safety5. Expert Advise6. Availability of Planting Stock7. Maintenance Costs8. Epidemics of Insects and Disease
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Biomes of the World
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Tropical Forest Biome - Distribution and Climate
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Coniferous Forest Biome - Distribution and Climate
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Cities Surveyed in each Biome
Tropical Forest SavannaBangkok BrasiliaRio de Janeiro LagosSingapore New Delhi
Broadleaf Evergreen ForestGrassland
Hong Kong Buenos AiresSydney JohannesburgTokyo TehranDeciduous Forest DesertNew York CairoLondon DubaiParis PhoenixMixed Deciduous-Coniferous Forest TundraBeijing MurmanskMoscow NuukStockholm ReykjavikConiferous Forest HighlandsJacksonville CuscoSeattle LhasaVancouver QuitoMediterrean Woodland-ScrubAthensLos AngelesTel Aviv
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Average Tree Species Richness in Cities in Different Biomes
Biome Average Number of Tree Species*Tropical Forest 35Broadleaf Evergreen 36Deciduous Forest 49Mixed Deciduous-Coniferous Forest 32Coniferous Forest 45Mediterranean Woodland-Scrub 49Savanna 51Grassland 41Desert 29Tundra 9 Highland 34* Trees in the public right-of-way
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Factors contributing to the variationin Urban Forest Species Diversity
1. Climate 2. Tree Species Richness of Local Biome3. History4. Expert Advise5. Spiritual/Psychological Values6. Availability of Planting Stock7. Epidemics of Insects and Disease8. Public Popularity
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Historical Factors Influencing Urban Forest Tree Species Diversity
1. Exploration2. Colonization3. National Pride
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John Bartram
Commonly Encountered English Park Trees Introduced by Bartram
Eastern White PineHoney LocustScarlet OakSilver MapleSouthern MagnoliaSugar MapleSweetgum SycamoreTulip Tree
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David Douglas
Commonly Encountered English Park Trees Introduced by Douglas
Douglas-fir Grand FirNoble Fir Sitka Spruce
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Oglethorpe’s Plan for Savannah, GA
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Tree Species Introduced to America during the British Colonial Period
Introduced Tree SpeciesItalian PoplarItalian CypressEnglish OakEuropean BirchPaper MulberryEnglish HollyWeeping Willow
43London
British Colonization and the spread of London Plane Tree
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Occurrence of London Plane treesin British Colonial Cities
Presence of London Plane Tree**British Non-BritishColonial Colonial
Biome* Cities(%) Cities(%)Deciduous Forest 100 100Grassland 100 50Broadleaf Evergreen 100 0Coniferous Forest 100 0
Average 100 38
* Biomes with cities in which London Plane tree was one of the top five mostfrequently encountered street tree species
** London Plane tree was one of the tops five most frequently encounteredspecies
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Modal Spacing of Treesin Boulevard Medians
City Mod al Boule var d tr ee
Spacing (ft.)
London 40
New York* 40
New Delhi* 40
Cairo* 40
Ho ng Kong* 40
Lagos* 40
Singa pore* 40
Vancouv er* 40
Syd ney* 50
Johanne sbu rg* 35
Par is 38
Seatt le 35
Athen s 30
Stockho lm 28
Tokyo 25
Moscow 20
Teh ra n 20
* Forme r British Colon ial City;
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National Pride
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47Boston Commons, ca. 1750
Lombardy Poplar
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Pennsylvania Avenue, Washington
Ca. 1800
1865
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National Pride
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WangFuJing Shopping District - Beijing
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Factors contributing to the variationin Urban Forest Species Diversity
1. Climate 2. Tree Species Richness of Local Biome3. History4. Expert Advise5. Spiritual/Psychological Values6. Availability of Planting Stock7. Epidemics of Insects and Disease8. Public Popularity
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Expert Advise1. Arborist’s Experience with Trees2. Maintenance costs3. Safety
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Number of Recommended Species for San Francisco
Number ofOrganization Recommended SpeciesFriends of the Urban Forest (2007) 54San Francisco Department of Urban Forestry (1998) 200
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Maintenance Problems influencing Tree Selection
Tree DebrisSidewalk and Curb DamageFrequent Pruning RequirementsSafety
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Bishop Ranch Business Park
Tree Debris
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Trees Planted at Bishop Ranch Business Park
Black locust Gledista triacanthosCallery pear Pyrus calleryanaCanary Island pine Pinus canariensisChinese pistache Pistacia chinensisCoast live oak Quercus agrifoliaCork oak Quercus suberCrape myrtle Lagerstroemia indicaDeodar cedar Cedrus deodaraEvergreen ash Fraxinus uhdeiHollywood juniper Juniperus chinensisHoney locust Robinia pseudoacaciaItalian stone pine Pinus pineaLombardy poplar Populus nigra ‘italica’London plane Platanus x acerifoliaRedwood Sequoia sempervirensTulip tree Liriodendron tulipfera
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Trees not Planted at Bishop Ranch Business Park
Cherry Prunus spp.Crabapple Malus spp.Gingko Gingko bilobaStrawberry Tree Arbutus unedoMulberry Morus spp.
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Messy Tree Fruit
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Sidewalk and Curb Damage
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London Plane Tree
Chinese Elm
Evergreen Ash
Frequent Pruning Requirements
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Expert Advise on Planting under Power Lines
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Space for Trees
20’
30’
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Recommended Number of Species (<25’ tall)
City “SafeTree” Other AuthoritiesSeattle 32 86 (Jacobson, 1989)Los Angeles 18 61 (Perry, 1989)Jacksonville 6 39 (Nelson, 2003)
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Safety Considerations for Treesin Traffic Circles and Medians
Traffic Circles - Berkeley, CA“No oak trees or other species characterized by having strong wood”
Medians - Palo Alto, CA“No trees in medians less than4’wide”“No trees that will reach reach a diameter greater than 12”ten years after planting”
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Sweetgum
Tree Debris and Safety
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Tulip Tree
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Chinese Elm and Branch Failure
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Factors contributing to the variationin Urban Forest Species Diversity
1. Climate 2. Tree Species Richness of Local Biome3. History4. Expert Advise5. Spiritual/Psychological Values6. Availability of Planting Stock7. Epidemics of Insects and Disease8. Public Popularity
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Spiritual/Psychological Value of TreesReligious Symbolism of TreesFeng ShuiEarly Childhood Environment
70Oakland
San Francisco
London
Trees Common to Cemeteries
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World’s Most Common Cemetery Trees
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Cities in which trees with religious symbolism are commonly used as street trees
City Tree Scientific NameBangkok Bo Tree Ficus religiosaNew Delhi Neem Tree Azadirachta indicaSingapore Bo Tree Ficus religiosaHong Kong Bo Tree Ficus religiosaDubai Ghaf tree Prosopis cineraria
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Bo Tree
Nepal
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Bo Tree
Bangkok
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Feng Shui
Tree Placement:Locate trees so they do not blockthe flow of energy through the house.Avoid tree placement in front ofdoors and windows.
Trees to be Avoided1. Trees that grow downward
• Weeping willow• California pepper tree
2. Trees with sharp pointed leaves• Holly• Santa Lucia fir
3. Trees with thorns• Honey locust• Silk cotton tree
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Psychological Importance of Trees
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Early Childhood Environment Hypothesis
Clare Cooper Marcus
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Danville, CA
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Preferred Species of Homeowners in Danville, CA(Wortheim, 1973)
Childhood Region Species PlantedNortheast Sugar Maple
Birch
Southeast Southern MagnoliaSweetgum
Central Rocky Mountains Blue SpruceGrand Fir
Southwest CottonwoodYellow pine
California RedwoodCoast Live Oak
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Factors contributing to the variationin Urban Forest Species Diversity
1. Climate 2. Tree Species Richness of Local Biome3. History
4. Expert Advise5. Spiritual/Psychological Values6. Availability of Planting Stock7. Epidemics of Insects and Disease8. Public Popularity
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Tree Nursery
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From: reenurseries.us
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South Lake Tahoe
Summer Cabin
Year Round Residence
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South Lake Tahoe Nursery
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Tree Species occurring around Summer Cabins before 1950
Tree Type Number of Species PercentConifer 6 67Hardwoods 3 33
Tree Type Number of Species PercentConifer 30 27Hardwoods 80 73
Trees offered for sale in Lake Tahoe Basin in 1995
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Factors contributing to the variationin Urban Forest Species Diversity
1. Climate 2. Tree Species Richness of Local Biome3. History
4. Expert Advise5. Spiritual/Psychological Values6. Availability of Planting Stock7. Epidemics of Insects and Disease8. Public Popularity
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American Elm - Dutch Elm Green Ash - Emerald Ash Borer
Angsana - Angsana Wilt Disease Horse Chestnut - Bleeding Canker Disease;Leaf Miner Moth
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Factors contributing to the variationin Urban Forest Species Diversity
1. Climate 2. Tree Species Richness of Local Biome3. History4. Expert Advise5. Spiritual/Psychological Values6. Availability of Planting Stock7. Epidemics of Insects and Disease8. Public Popularity
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Trends in Species Planting - Tokyo
From: Cheng and McBride, 2000
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Age Structure of Sweetgum and California Pepper TreeMenlo Park, CA 1975
100- SweetgumCalifornia Pepper
80-
% 60-
40-
20-
0-19 20-39 40-59 60-79 80-99 100-120 Age
Sweetgum
California Pepper
Age Structure of Sweetgum and California Pepper TreeMenlo Park, CA 1975
100- SweetgumCalifornia Pepper
80-
% 60-
40-
20-
0-19 20-39 40-59 60-79 80-99 100-120 Age
Maintenance and Preference:Menlo Park, California
Age Structure of Sweetgum and California Pepper TreeMenlo Park, CA 1975
100- SweetgumCalifornia Pepper
80-
% 60-
40-
20-
0-19 20-39 40-59 60-79 80-99 100-120 Age
1975
1905
18851925
1945
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Trends in Species Diversity
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Trends in Tree DiversityCities with street trees frequencie s of 50 percent or greater
Biome City Species Frequen cy
London London Plane Tree 67Decid uous Forest
Par is London Plane tr ee 67
Live Oak 70Conife r Forest Jacksonville
Laur el O ak 50
Moscow Commo n Lim e 83
Beijing Japane se Pagoda T ree 56
Mixed Decid uou s-
Coni ferous Forest
Stockho lm Commo n Lim e 50
Bueno s Aires Green Ash 67Grassland
Teh ran Or ien tal Pl ane Tree 54
Highl and Lhasa Chin ese Wh ite Poplar 67
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American Cities European CitiesCity Species Richness* City Species Richness*New York 2.4 London 1.5Los Angeles 2.5 Athens 2.2Seattle 2.2 Stockholm 1.2Phoenix 4.0 Cairo 1.1Average 2.8 Average 1.5* Average number of street tree species in 25 sample plots
Sample plot 300’ long, trees on both sides of the street recorded
Species Richness in American vs. European Cities
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Consequences of Trends in Diversity
1. Risk of Disease or Insect Epidemics2. Risk of Widespread Mortality due to Abiotic Factors3. Homogenization of Urban Forest Aesthetics
95Ames, Iowa - 1969 Ames, Iowa - 1970
Risk of Disease or Insect Epidemics
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Risk of Widespread Mortality due to Abiotic Factors
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Global Climate Change
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Average Maximun Temperature* = 69o FExtreme Maximum Temperature = 97o F
Average Maximun Temperature* = 75o FExtreme Maximum Temperature = 108o F
San Francisco
Tijuana
* July Temperature
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Global Climate Change
Average Maximun Temperature* = 98o FExtreme Maximum Temperature = 118o F
ReddingAverage Maximun Temperature* = 108o FExtreme Maximum Temperature = 123o F
Palm Springs
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Aesthetics of the Urban Forest
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Moscow London Beijing
London Plane = 67%
Pagoda Tree = 56%
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Common Lime = 83%
Lack of Aesthetic Variety
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Urban Forest DiversityRecommendations
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RecommendationsBarker (1975): Species = 5%Grey and Deneke (1986): Species 10-15%Moll (1989): Genus = 10%; Species = 5%Santamour (1990): Family = 30%; Genus = 20%; Species = 10%Miller and Miller (1991): Proven Species = 10%Richards (1993): No numerical limits on proven species;
Diversity of size classes more importantRaupp et al. (2006): Diversify in response to known pest problems
(e.g., Emerald Ash Borer, Asian Longhorn Beetle)
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“Urban foresters should take steps now to diversify the types of trees that are planted in cities to avoid catastrophic tree losses or massive and expensive tree protection programs.”
Michael J. Raupp, Anne Buckelew Cumming, and Erin C, Raupp, 2006
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End
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Most Frequently Encountered Street Treesin Survey of 33 Cities
Betula pendula10, Silver Birch
Populus x canadensis9. Carolina poplar
Pterocarpus indicus8. Angsana
Jacaranda mimosaefolia7. Jacaranda
Gleditsia triacanthos6. Honey Locust
Acer platanoides5. Norway Maple
Pheonix canariensis4. Canary Island Date palm
Tilia europea3. Common Lime
Sorbus aucuparia2. Rowan
Platanus x acerifolia1. London Plane Tree
Scientific NameCommon Name
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Trees offered for sale in Tahoe Cityand South Lake Tahoe in 1995
Species (and cultivars) NumberTotal 110Hardwoods 80Conifers 30
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