6/11/2012
Quantifying Carbon Storage in Urban Trees
Paula J. Peper
Ecologist
Urban Ecosystems & Social Dynamics
Davis, California
U.S. Department of Agriculture
Pacific Southwest Research Station
Science that makes a difference
Today
• Definitions
• Forest vs. urban trees
– How little we know
• Work with what we have
– The error of (all of) our ways
– Expect change
• The basics – growth and biomass
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6/11/2012
Definitions
• DBH – tree bole
diameter at breast
height (1.37 m or 4.5 ft)
• Tree Height – total
height from ground level
to top of tree
• Need DBH or DBH and
Height to estimate
volume and biomass of
tree
Omit leader from total
tree height
measurement.
Measure to white
line.
• Volume – volume
of the wood only—
bole, branches,
twigs, but no
leaves
– Use volume to
determine
biomass of tree
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6/11/2012
Biomass – the dry
weight (dw) of wood in
the tree (no leaves)
• Aboveground
• Total biomass
– 1.282 constant to
add roots
Carbon (C)
Remove all the moisture from the tree
– half of the dry weight of the tree is
carbon
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6/11/2012
Stored and Sequestered CO2
• Sequester – save, reduce, or prevent from
escape into the atmosphere
• 1 t of carbon is contained in 3.67 t of CO2
• If a tree stores 1 t of carbon each year it
“sequesters” about 3.67 t/yr
Reporting Unit
Short ton = 2,000 lbs
Metric tonne or ton = 2,204 lbs
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6/11/2012
What is Needed to Calculate Carbon Storage?
• Need tree dbh or dbh
and height (growth)
• Volume or biomass
equations
• Wood density (think
pine vs. oak)
– DW Density
Photo credit: Tapenade
DW Wood Density
• Ratio of oven-dry mass
of wood sample divided
by mass of water
displaced by its green
volume
• Measured wt of water
= sample’s volume
– kg/m3
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6/11/2012
State of the Science: Cart before the Horse?
• Forest vs. urban
– Growth models
• Few urban
• Use forest?
– Volume and biomass
equations
– Wood density
Photo credit: www.whatwouldthefoundersthink.com
Not an exact science but an ever-changing body of knowledge
Forest vs. Urban Trees
Quercus falcata
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6/11/2012
Organ and Carbon Partitioning
• Distribution as
percentage of whole
tree of
–
–
–
–
–
Roots
Bole
Branches
Twigs
Leaves
• Partitioning driven by
light, water, soil
nutrient availability
Illustration courtesy of Davey Tree Expert Company
Honolulu to NYC and Orlando
• 17,000 trees
• 365 sets of growth
curves (1,825
equations)
• 171 unique species
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6/11/2012
Comparisons and trends
Silver Maple
• Overlap
80
BIS
70
BOI
60
CLT
50
CYS
40
FNL
30
IND
20
JFK
10
MOD
–
–
–
–
–
Sweetgum 10
Honeylocust 10
Silver maple 9
Callery pear 9
Green ash 8
0
Years After Planting
15
Silver Maple
90
80
70
100%
60
Growth (ft)
Height (ft)
90
64 ft
50
40
44 ft
30
59%
20
10
0
0
5
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
Cheyenne
Years
Ft. Collins
Center for Urban Forest Research
Modesto
16
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6/11/2012
Management
Center for Urban Forest Research
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Tree Size Error
• Only 35-70 trees
measured per species
• Often few old trees
• Size estimates are
“averages” for the
trees measured
• New web-based
carbon calculator
provides adjustment
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6/11/2012
Volume and Biomass Equations
• Hundreds in forest
literature
• Forest general
equations
• 26 common species in
urban
– Apply taxonomically
based on form
• Urban general
equations
• Forest
– Predominantly based
on dbh alone
• Forest general
– Based on mixed
hardwood and
softwood stands
• Forest – most predict
biomass, not volume
and for merchantable
timber
Carbon Calculator
• 1st – urban volume
• 2nd – forest species &
region-specific
• 3rd - urban general
over forest general
– Or those equations that
incorporate use of dw
density factor
– TCC reduces choices,
provides consistency
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6/11/2012
DW Density Varies
Variation:
•
•
•
•
Within the tree
During the life of the tree
Between individuals
Branches and outer bole
lighter than pith
Most values today:
10-30 cm trees (<12 in)
10-30 samples (bole)
Waist to breast height
Global Wood Density
Database
Basics of Calculating:
from Biomass to Annually Sequestered CO2
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Single London Plane Volume
21 in
47 ft
0.002
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Single London Plane AG Biomass
1026 kg
2262 lbs
0.81 kg
1.8 lbs
Total Carbon
658 kg
1451 lbs
0.5 kg
1.1 lbs
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6/11/2012
Total Stored CO2
2415 kg
5324 lbs
1.9 kg
4.2 lbs
CO2 Sequestered Annually
Total stored CO2
2
minus Total stored CO2
1
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6/11/2012
Total Stored CO2
2415 mt
2662 t
Questions?
© Peter Welleman
www.CartoonStock.com
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