urban forest diversity - uc davis plants · weeping willow. 43 london british colonization and the...

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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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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




50

WangFuJing Shopping District - Beijing



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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



Tulip Tree



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Chinese Elm and Branch Failure



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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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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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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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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



80-

% 60-

40-

20-

0-19 20-39 40-59 60-79 80-99 100-120 Age

Maintenance and Preference:Menlo Park, California



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





Average Maximun Temperature* = 69o FExtreme Maximum Temperature = 97o F


San Francisco

Tijuana

* July Temperature

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Global Climate Change


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%



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

urban forest diversity - uc davis plants · weeping willow. 43 london british colonization and the...

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