Urban Forest Diversity

1
Urban Forest Diversity

• Joe R. McBride
• Department of Landscape Architecture and
  Environmental Planning
• University of California
• Berkeley, CA

2
Objectives

• 1.Define the term urban forests
• 2. Describe measurement of species composition in
  urban forests
• 2. Identify factors contributing to urban forest
  species diversity
• 3. Identify trends in species diversity
• 4. Discuss the potential consequences of these
  trends
• 5. Review recommendations for establishment and
  maintenance
• of urban forest diversity

3
The Urban Forest - Berkeley, CA
4
Urban Environments for Trees
Boulevards
Streets
Parks
Cemeteries
Yards
Marinas
Wildlands
Campuses/Riparian Zones
5
Measures of Species Composition
1. Species Richness 2. Species
Evenness 3. Species Diversity
6
Species Richness
Number of species in a sample
unit
7
Tree Species Richness in Three California
Cities
City Tree Species
Richness South Lake Tahoe
35 Menlo Park 145 Santa
Barbara 1,226
8
Species Evenness Uniformity of
occurrence of a species across a number of samples
9
London Plane Tree (Platanus x acerifolia) Freque
ncy 25
Berkeley, CA
10
Flax Leaf Melaluca (Melaleuca linarifolia)
Frequency 1
Berkeley, CA
11
Species Diversity Measure of species richness
and evenness
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Species Diversity
Berkeley, CA
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Simpsons Diversity Index D 1
D diversity index ?(pi)2
pi proportion of
individuals in the
population
belonging to species i
14
Simpsons Divesity Indicies of Hypothetical
Street Trees
3
Site 1
Site 2
Site 3
Proportion of Population Represented by Species
(pi)

• Site A B C D Simpsons Index
• 1 0.50 0.50 0 0 2.00
• 2 0.425 0.25 0.20 0.125 2.98
• 3 0.25 0.25 0.25 0.25 4.00

Species
15
Comparison of Urban Forest Diversity
City Simpsons
Diversity Index New Orleans, LA
7.6 Athens, Greece
11.4 Hong Kong, China 12.7 Anne
Arundel, MD 20.1
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Comparison of Urban Forest Diversity
City Simpsons
Diversity Index Mt. Vernon, Ohio
2.1 Bretenahl, Ohio 2.2 Newark, New
jersey 2.3 Bexley, Ohio
2.4 Austin, Minnesota 2.7 Vienna,
Virginai 2.9 Perrysburg, Ohio
3.0 Eugene, Oregon 3.3 La canada,
California 3.4 Los Angeles, California 3.9
From McPherson and Rowntree,
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Factors contributing to the variation in Urban
Forest Speices Diversity

• 1. Climate
• 2. Tree species richness of local biome
• 3. History
• 2. Spiritual/Psychological Values
• 4. Safety
• 5. Expert Advise
• 6. Availability of Planting Stock
• 7. Maintenance Costs
• 8. Epidemics of Insects and Disease

18
Climate and Urban ForestSpecies Richness
Analysis
19
Koppens Climate Classification
From FAO - SDRN - Agrometeorology Group - 1997
20

Cities Surveyed for Climate Analysis
21
Urban Forest Species Richness in Relation to
Climate Types

22
Urban Forest Species Richness in Relation to
Climate
50

A Tropical Moist
Climates
B
Dry Climates C Moist,
Mid-latitude Climates

with mild winters 40
D Moist, Mid-latitude Climates
with cold winters
E Polar Climates

30
20 10




A B C
D E Koppen Climate

23
Frost Hardiness Zone Map
24
Urban Forest Species Richness in Relation to
Hardiness Zones
25
Urban Forest Species Richness in Relation to
Hardiness Zones
50


3-4 -40 to -20


5-6 -20 to 0
7-8 0 to 20

9-10 20 to 40
40
11-12 40
to 60
13-14 60 to 80


30
20 10




3-4 5-6 7-8
9-10 11-12
13-14 Hardiness Zone
26
Tree Species Richness of Local Biome and Urban
Forest Species Diversity
Rio de Janeiro
27

• Biomes of the World

28
Tropical Forest Biome - Distribution and Climate
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Tropical Forest Biome
Tropical Forest Tree Species Richness Location
Number of Species Costa Rica 433
Brazil 283 Malaysia 277 From Richards,
1973 Lantham and Ricklefs, 1993
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Coniferous Forest Biome - Distribution and Climate
31
Coniferous Forest Biome
Coniferous Forest Species Richness Location Numbe
r of Species Mt. Rainier 31 Olympic
Peninsula 25 Warner Mountains 13 From Lantham
and Ricklefs, 1993 Kimmins, 2004
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Cities Surveyed in each
Biome Tropical Forest Savanna Bangkok Brasil
ia Rio de Janeiro Lagos Singapore New
Delhi Broadleaf Evergreen Forest Grassland Hong
Kong Buenos Aires Sydney Johannesburg Tokyo
Tehran Deciduous Forest Desert New
York Cairo London Dubai Paris Phoenix Mix
ed Deciduous-Coniferous Forest Tundra Beijing M
urmansk Moscow Nuuk Stockholm Reykjavik Coni
ferous Forest Highlands Jacksonville Cusco Se
attle Lhasa Vancouver Quito Mediterrean
Woodland-Scrub Athens Los Angeles Tel Aviv
33
Average Tree Species Richness in Cities in
Different Biomes

• Biome Average Number of Tree Species
• Tropical Forest 35
• Broadleaf Evergreen 36
• Deciduous Forest 49
• Mixed Deciduous-Coniferous Forest 32
• Coniferous Forest 45
• Mediterranean Woodland-Scrub 49
• Savanna 51
• Grassland 41
• Desert 29
• Tundra 9
• Highland 34
• Trees in the public right-of-way

34
Relative Tree Species Richness of Biomes
35
Relative Tree Species Richness of Biomes and
Urban Forests
36
Historical Factors Influencing Urban Forest Tree
Species Diversity

• 1. Exploration
• 2. Colonization

37
John Bartram

• Commonly Encountered English Park Trees
  Introduced by Bartram
• Eastern White Pine
• Honey Locust
• Scarlet Oak
• Silver Maple
• Southern Magnolia
• Sugar Maple
• Sweetgum
• Sycamore
• Tulip Tree

38
David Douglas

• Commonly Encountered English Park Trees
  Introduced by Douglas
• Douglas-fir
• Grand Fir
• Noble Fir
• Sitka Spruce

39
Oglethorpes Plan for Savannah, GA
40
Tree Species Introduced to America during the
British Colonial Period

• Introduced Tree Species
• Italian Poplar
• Italian Cypress
• English Oak
• European Birch
• Paper Mulberry
• English Holly
• Weeping Willow

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Lombardy Poplar
Boston Commons, ca. 1750
42
Pennsylvania Avenue, Washington
ca, 1800
1865
43
London
44
Most Frequently Encountered Street Trees in
Survey of 33 Cities
45
Occurrence of London Plane trees in British
Colonial Cities

• Presence of London Plane Tree
• British British
  Non-British
• Colonial Colonial
  Colonial
• Biome Cities () Cities ()
  Cities()
• Deciduous Forest 50
  100 100
• Grassland 33 100
  50
• Broadleaf Evergreen 33
  100 0
• Coniferous Forest 33 100
  0
• Biomes with cities in which London Plane
  tree was one of the top five most
• frequently encountered street tree species
• London Plane tree was one of the tops
  five most frequently encountered
• species

46
Modal Spacing of Trees in Boulevard Medians
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Oakland
Spiritual Symbolism of Trees
San Francisco
London
48
Bo Tree
Nepal
49
Bo Tree
Bangkok
50
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Cities in which trees with religious symbolism
are commonly used as street trees

• City Tree Scientific Name
• Bangkok Bo Tree Ficus religiosa
• New Delhi Neem Tree Azadirachta indica
• Singapore Bo Tree Ficus religiosa
• Hong Kong Bo Tree Ficus religiosa
• Dubai Ghaf tree Prosopis cineraria

52
Feng Shui
Tree Placement Locate trees so they do not
block the flow of energy through the house. Avoid
tree placement in front of doors and windows.
Trees to be Avoided 1. 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
54
Danville, CA
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Preferred Species of Homeowners in Danville,
CA(Wortheim, 1973)

• Childhood Region Species Planted
• Northeast Sugar Maple
• Birch
• Southeast Southern Magnolia
• Sweetgum
• Central Rocky Mountains Blue Spruce
• Grand Fir
• Southwest Cottonwood
• Yellow pine
• California Redwood
• Eucalyptus

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Factors contributing to the variation in
diversity of tree species

• Ecological Factors
• 1. Climate
• 2. Tree species richness of biome
• Other Factors
• 1. Historical
• 2. Spiritual
• 3. Psychological
• 4. Safety
• 5. Expert Advise
• 6. Commercial
• 7. Maintenance
• 8. Epidemic Mortality

57
Safety Considerations for Trees in 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 than
• 4wide
• No trees that will reach reach
• a diameter greater than 12
• ten years after planting

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Influence of Expert Advise of Urban Forest
Species Diversity

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Number of Recommended Species for San Francisco

• Number of
• Organization
  Recommended Species
• Friends of the Urban Forest (2007)
  54
• San Francisco Department of Urban Forestry (1998)
  200
• P.G. E. (1957)
  15

61
Expert Advise on Planting under Power Lines
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Tree Height Categories
Low Mature gt25 Medium Mature 30-45 Large
Mature gt 45 From Minnesota Tree Safe Program
Tree Height Categories Low Mature lt
25 Medium Mature 30-45 Large
Mature gt 45Minnesota SafeTree Program (2002)
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Recommended Number of Species (lt25 tall)
City SafeTree Other Authorities Seattle
32 86 (Jacobson, 1989) Los Angeles
18 61 (Perry, 1989) Jacksonville 6 39
(Nelson, 2003)
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Availability of Planting Stock
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South Lake Tahoe

• Summer Cabin

Year Round Residence
66
South Lake Tahoe Nursery
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Composition of Natural Forest and Nursery Trees

• Tree Type Natural Forest () Nursery ()
• Conifer 63 27
• Hardwoods 37
  73

68
Trees offered for sale in Tahoe City and South
Lake Tahoe

• Species (and cultivars) Number
  Percent of Total
• Total
  110 100
• Hardwoods 80
  73
• Native Hardwoods 3
  3
• Conifers 30
  27
• Native Conifers 5
  4

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Maintenance Problems influencing Tree Selection

• Tree Debris
• Sidewalk and Curb Damage
• Frequent Pruning Requirements

70
Tree Debris
Bishop Ranch Business Park
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Trees planted at Bishop Ranch Business Park

• Black locust Gledista triacanthos
• Callery pear Pyrus calleryana
• Canary Island pine Pinus canariensis
• Chinese pistache Pistacia chinensis
• Coast live oak Quercus agrifolia
• Cork oak Quercus suber
• Crape myrtle Lagerstroemia indica
• Deodar cedar Cedrus deodara
• Evergreen ash Fraxinus uhdei
• Hollywood juniper Juniperus chinensis
• Honey locust Robinia pseudoacacia
• Italian stone pine Pinus pinea
• Lombardy poplar Populus nigra italica
• London plane Platanus x acerifolia
• Redwood Sequoia sempervirens
• Tulip tree Liriodendron tulipfera

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Tree Debris and Safety
Sweetgum
Chinese Poplar
73
Sidewalk and Curb Damage
74
Frequent Pruning Requirements
London Plane Tree
Evergreen Ash
Chinese Elm
75
Maintenance and Preference
California Pepper
Sweetgum
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Factors contributing to the variation in
diversity of tree species

• Ecological Factors
• 1. Climate
• 2. Tree species richness of biome
• Other Factors
• 1. Historical
• 2. Spiritual
• 3. Psychological
• 4. Safety
• 5. Expert Advise
• 6. Commercial
• 7. Maintenance
• 8. Epidemic Mortality

77
Epidemic Tree Mortality
78
American Elm - Dutch Elm
Sweetgum - Annosus root rot
Angsana - Angsana Wilt Disease
Horse Chestnut - Bleeding Canker
Disease Leaf Miner Moth
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Trends in Tree Diversity - Tokyo
From Cheng and McBride, 2000
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Trends in Tree Diversity
Species Richness in American vs. European Cities
American Cities European
Cities City Species Richness
City Species Richness New York 2.4
London 1.5 Los Angeles 2.5
Athens 2.2 Seattle 2.2
Stockholm 1.2 Phoenix 4.0
Cairo 1.1 Average 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
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Trends in Tree Diversity
82
Trends in Tree Diversity
83
Trends in Tree Diversity
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Consequences of Trends in Diversity

• 1. Risk of Disease or Insect Epidemics
• 2. Risk of Widespread Mortality due to Abiotic
  Factors
• 3. Homogenization of Urban Forest Aesthetics

85
Ames, Iowa - 1969
Ames, Iowa - 1970
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Recommendations for Urban Forest Diversity

• Barker (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
  important
• Raupp et al. (2006) Diversify in response to
  known pest problems
• (e.g., Emerald Ash Borer, Asian Longhorn
  Beetle)

89

• 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