Managing Temperate Forests for
Carbon Sequestration
Mark J. Ducey
Professor of Forest Biometrics and
Senior Fellow, The Carsey Institute
University of New Hampshire
Overview
•
•
•
•
•
•
Scope
The Most Important Thing
The Faulty Bucket Model
Some Myths
The Scary Part
What Do We Really Know, and What
Should We Do About It?
Temperate Forests Are...
• Extremely Variable
–
–
–
–
–
Environmentally
Ecologically
Socially
Historically
No one-size-fits-all
prescription
• Complex
– trees, animals, people,
land, water, climate...
Carbon is not necessarily...
• What a particular
market values
• What a particular
international
agreement says
• What a particular
inventory/conversion
strategy calculates
• What a particular
model predicts
The Most Important Thing
• To store carbon in forests, WE MUST HAVE
FORESTS.
• Land cover conversion (change in area of
forests) can swamp our best efforts at managing
carbon density (Mg/ha).
• Forests MUST be valued (produce values) to be
a competitive land cover.
• “Bad” forests are better than no forests.
IMPERATIVES: Conserve forest area, and
conserve productive capacity.
Spatial patterns of forest aboveground biomass (AGB, Mg ha-1, dry weight)
estimates a) based on 1992 AVHRR derived land-cover map and reflectance
data (the results have been adjusted by sensor difference); and b) based on
2001 MODIS derived land-cover map and reflectance data. Zheng, Heath,
and Ducey 2008: EMAS 44:67-79.
The Faulty Bucket Model
• The (Faulty Bucket) Model
• The Faulty (Bucket) Model
“All models are wrong; some models are
useful.” – G.E.P. Box
Atmosphere
Live
Emitted
Biomass
w/ Energy Capture
Necromass
Emitted
Soil
w/o Energy
Capture
Long-Term
Products
Short-Term
Products
Landfill
The Mathematical
[and other] Goal(s)
• Maximize the carbon stored in all the nonatmospheric buckets over time
• Store carbon in the buckets in the most
cost-efficient manner
• Store carbon in the buckets sustainably
Parameters
[These particular values are fictitious...]
Gross Production
4 Mg/ha/yr
Mortality Rate
0.02 Mg/Mg/yr
Necromass to Atmosphere
0.04 Mg/ha/yr
Necromass to Soil
0.005 Mg/ha/yr
Soil to Atmosphere
0.003 Mg/ha/yr
LT Prod to Atmosphere
0.01 Mg/ha/yr
LT Prod to Landfill
0.02 Mg/ha/yr
ST Prod to Atmosphere
0.10 Mg/ha/yr
ST Prod to Landfill
0.30 Mg/ha/yr
Landfill to Atmosphere
0.005 Mg/ha/yr
Carbon Storage
350
300
Energy
Landfill
Short-Term
Long-Term
Necromass
Biomass
Soil
200
150
100
50
Year
96
90
84
78
72
66
60
54
48
42
36
30
24
18
12
6
0
0
Mg/ha
250
Carbon Storage
700
600
Energy
Landfill
Short-Term
Long-Term
Necromass
Biomass
Soil
400
300
200
100
Year
496
465
434
403
372
341
310
279
248
217
186
155
124
93
62
31
0
0
Mg/ha
500
An “Optimal” Solution
• Displaced fossil fuel use has an “infinite”
shelf life
• It is mathematically optimal to divert ALL
production to that bucket, and zero the
standing live carbon pool so NO leakage
occurs
• Solution: manage forests as short-rotation
biomass farms (or replace with annual
crops)
Carbon Storage
2500
Energy
Landfill
Short-Term
Long-Term
Necromass
Biomass
Soil
1500
1000
500
Year
496
465
434
403
372
341
310
279
248
217
186
155
124
93
62
31
0
0
Mg/ha
2000
Objections
• What about nutrient depletion?
• What about loss of soil carbon?
• Is fossil fuel substitution really forever?
– Does it just postpone fossil fuel drawdown?
– How long can substitution continue?
– In the next 25, 50, 100 years...
• either we find economically viable alternatives to
mass consumption of fossil carbon...
• or we don’t
Another “Optimal” Solution
• Do... absolutely nothing.
• Let forests approach their asymptotic
maximum carbon density.
• Cut nothing. Use nothing.
– At least, use nothing from the forest.
Substitute non-renewable and/or energyintensive materials like concrete, steel,
aluminum, and plastics.
– Maybe we can use someone else’s forests.
Carbon Storage
350
300
Energy
Landfill
Short-Term
Long-Term
Necromass
Biomass
Soil
200
150
100
50
Year
96
90
84
78
72
66
60
54
48
42
36
30
24
18
12
6
0
0
Mg/ha
250
Can’t We Be More Creative?
• Thin forests from below, capturing
mortality and diverting that carbon to
bioenergy/materials substitution
• Use crown thinning to accelerate the
development of large-diameter trees that
can eventually become long-term products
• Use improvement thinning to focus
production on high-quality trees with the
potential to become long-term products
Scary, Radical Stuff
• Where biofuels are an important goal, use
standards (interspersed trees grown on
longer rotations) to provide durable carbon
sinks and other ecosystem values
• Find ways to incentivize longer rotations,
both to enhance the standing “bucket” and
allow time for development of large trees
The Upshot
“A sustainable forest management strategy
aimed at maintaining or increasing forest
carbon stocks, while producing an annual
sustained yield of timber fibre or energy
from the forest, will generate the largest
sustained mitigation benefit.“
-- IPCC 4th Assessment Report
Shouldn’t We Avoid Even-Aged
Management Altogether?
• The soil carbon “penalty” for clearcutting
• Single-tree selection is kinder, gentler,
prettier
• Single-tree selection is more “natural” and
“harmonious”
• Why not only cut trees that can provide
durable in-use pools, and let Nature take
care of the rest?
Carbon Storage
300
Energy
Landfill
Short-Term
Long-Term
Necromass
Biomass
Soil
200
150
100
50
Year
90
96
78
84
66
72
54
60
42
48
30
36
18
24
6
12
0
0
Mg/ha
250
Selection System Reality
• Single-tree selection depends on
continuous, dispersed recruitment for
sustainability
• That means overstory stocking must be at
a low density
• Even at low densities, such systems tend
to exclude intolerant and mid-tolerant
species, and reduce tree diversity
USFS northern hardwood guide (RP-NE-603):
B=70 ft2/ac, D=21 inches,q=1.5 (2-inch classes)
BDq vs. Regulated Even-Aged Forest:
Northern Hardwoods
Single-tree selection:
B=16 m2/ha, ACBAR=4 Mg/m2
Aboveground tree carbon=64 Mg/ha
Species composition: beech, hemlock, red maple
Even-aged (or patch selection):
After adjustment of Smith et al. (GTR-345) curves to
aboveground tree carbon, 64 Mg/ha is the
landscape average for a 92 year rotation.
Species composition: full northern hardwoods
Disturbance and Change
• Catastrophic disturbance happens
• The response of forests (strain) to a set of
circumstances (stress) often depends
critically on forest structure
• Example: western US forests and fire
exclusion
• Example: European spruce plantations
and wind
Disturbances Happen
• We can’t completely avoid fire
• We can’t avoid hurricanes
• We can’t avoid species invasions
– but we sure could try harder
• We can’t avoid climate change
– but we sure could try harder
• We can’t avoid economic policies that
promote liquidation of our private forests
– but we sure could try harder
If we want to manage for C...
• Manage for resistance to catastrophic
disturbance
• Manage for resilience to catastrophic
disturbance
• Manage forests as a diverse portfolio
– think α, β, and γ diversity
– think genetic diversity
– think acclimation and adaptation to change
C is in at-risk Tsuga canadensis?
Total tree carbon in “Eastern Hemlock”
forest type:
Connecticut
1.87 Tg
Maine
Massachusetts
20.68 Tg
6.95 Tg
New Hampshire
New York
7.47 Tg
27.06 Tg
Rhode Island
Vermont
TOTAL
0.19 Tg
11.76 Tg
75.98 Tg
Source: COLE LITE (http://ncasi.uml.edu/COLE/).
By comparison, net sequestration by US forests is ~640 Tg C/yr.
NZ Native Forests
• Considered
“protected”
• Massive invasive
species issues
(possums, rats,
plants)
• Is a restoration
opportunity being
missed?
People Matter.
Temperate Forest C?
• Have forests
• Have forests that people want
• Have forests that are resistant, resilient,
and diverse
• Explore multiple, adaptable solution sets
• Recognize variable ecological and social
contexts
• NO ONE-SIZE-FITS-ALL-SOLUTIONS