Managed forest contribution to carbon sequestration under a rising atmospheric CO2 Objectives: Forest carbon is a cycle Define forest carbon sequestration Summarize what is known about how rising CO2 affects tree growth and forest health. Carbon management under rising CO2. What can be done to increase or enhance carbon sequestration?

1. Managed Forest Contribution to
Carbon Sequestration Under a
Rising Carbon Dioxide Regime
Chris A. Maier
Research Biological Scientist
USFS, Southern Research Station - RWU 4160
Forest Genetics and Ecosystems Productivity
Research Triangle Park, NC
919-549-4072
cmaier@fs.fed.us
2014 Southeastern Regional Forest
Landowner and Manager Conference,
Valdosta, GA

2. SRS-4160 – Forest Genetics and Ecosystems
Productivity
USDA Forest Service
Research and Development
www.fs.fed.us/research
Southern Research Station (SRS)
www.srs.fs.fed.us
Mission: To advance the scientific
understanding of the roles of genetics,
environment, and their interactions to
provide guidelines and tools for
improving the sustainable productivity
of southern forest ecosystems.
Research Focal areas:
Genetics and Genomics
Physiological Processes
Carbon and Nutrient Cycling
*
*

3. SRS-4160: Research Studies
Forest Productivity and
Resource Availability Forest Response to Elevated
CO2 and soil nutrition
Longleaf Pine (P.
palustris) Restoration
Genotype x Silviculture
‘Cross Carbon Study’
Cold tolerance and water
use in short-rotation
Eucalyptus benthamii
SETRES
Biomass production for
bioenergy and biofuels

4. Managed forest contribution to carbon
sequestration under a rising atmospheric CO2
• Objectives:
– Forest carbon is a cycle
– Define forest carbon sequestration
– Summarize what is known about how rising CO2
affects tree growth and forest health.
– Carbon management under rising CO2. What can
be done to increase or enhance carbon
sequestration?

5. Atmospheric CO2 is increasing rapidly
Projected to reach 550
ppm by 2050.

6. The Carbon Bathtub
Forest and grasslands remove about a third of the additional CO2

7. Atmospheric CO2 is an environmental paradox
(Beedlow et al. 2004)
– CO2 is a substrate for photosynthesis and essential
for all life
• Photosynthesis increases with increasing CO2
• Plant growth benefits from elevated CO2: “CO2 fertilization effect”
– Greenhouse gas
• Rising atmospheric CO2 and other greenhouse gases (e.g. CH4,
CFCs, and others) will most likely occur in conjunction with cyclical or
linear changes in other climatic factors (temperature and precipitation
regimes.
• Changes in climate will be more severe in some areas
• However, only modest changes in temperature and precipitation are
predicted for most of the southern US through 2050.

8. Can forest management be optimized to
harness the benefits and mitigate the
problems associated with increases in
atmospheric CO2?
Forest Carbon Sequestration:
the absorption and storage of
carbon from the atmosphere in plant biomass,
detritus, soil, and products

9. Forest management and carbon
sequestration: Approaches
• No management – carbon reserves in old growth
forests
• Extensive management – long rotations, fewer
extractions, maintain forest structure
• Intensive management – shorter rotations,
frequent extractions, substitute wood for durable
products, and bioenergy

10. Managing forest for C sequestration is supported by
international scientists and policy makers as a
strategy for mitigating anthropogenic CO2 emissions
“In the long term, a sustainable forest management strategy aimed
at maintaining or increasing forest carbon stocks, while producing an
annual sustained yield of timber, fiber, or energy from the forest, will
generate the largest sustained mitigation benefit.”
4th UN Intergovernmental Panel on Climate Change (IPCC) (2007)
“Increasing both forest stocks and timber harvest will buy time while
we learn more about how trees absorb carbon”
Bellassen and Luyssaert, Nature 2014

11. Paper
Wood
Above-ground Biomass
Major influences: Productivity
Rotation length
Major influences: soil type
management
climate
in situ Pools
ex situ Pools
Atmospheric CO2
Below-ground Biomass
(including forest floor)
Overall Major influences: Land Use
Economics
Major influences: Ownership type
Product classes
Economics
CO2
CO2
CO2
CO2
CO2
CO2
Conceptual model of carbon sequestration via
southern pine forestry
Source: Johnsen et al. JOF 2001

12. Carbon Storage in a Pine
Plantation
Carbon sequestration
must be understood over
multiple rotations
Source: Maier and Johnsen 2007 GTR-SRS-121

13. The Forest Carbon Cycle
Ecosystem Carbon Pools and Fluxes
• Pools:
– Foliage, stems, branches
– Roots
– Litter (above-, below-ground)
– soil
• Processes:
– Photosynthesis
– Respiration
– Carbon allocation
– Decomposition
• Variables that regulate carbon fluxes and
storage:
– Environment: temperature, precipitation, CO2
– Soil nutrition and hydrology
– Species
– Site history
– Pests and pathogens
From: Landsberg and Gower 1997

14. Photosynthesis: “CO2 fertilization effect"
6CO2 + 6H2O + energy C6H12O6 + 6O2
Pinus taeda
Eucalyptus benthamii
0 200 400 600 800 1000 1200 1400 1600 1800 2000
[CO2] (ppm)
Net Photosynthesis ( mol m-2s-1)
40
30
20
10
0
• Photosynthesis increases with CO2
• 30-50% at 550 ppm
• Elevated CO2 decreases stomatal conductance
and increases water use efficiency
sugar

15. How sensitive are forests to rising CO2?
• Productivity
• Nutrient supply and demand
• Water use
• Competitive relationships
• Seed production potential
• Pathogens and pest relationships

16. Will CO2 fertilization increase forest carbon sequestration
under all circumstances and/or alter carbon cycling?
Biomass
550 ppm CO2 - Scenario I
Present
550 ppm CO2 - Scenario II
Increase Initial growth rate, carrying capacity, or both?
Groninger et al. 1999
Time

17. Source: Maier et al. 2002 Tree Physiology
current year, July
SETRES: Elevated CO2 A – ambient CO2
ambient CO2
amb+200 CO
E – elevated CO2
unfertilized fertilized
Asat( mol m-2s-1)
8
6
4
2
0
unfertilized fertilized
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Annual Stem Growth
(kg C m2 ground)
A
E
A
E
On this very nutrient poor site:
• Elevated CO2 increased photosynthetic rate in
unfertilized and fertilized foliage.
• Elevated CO2 only increased growth when
trees were fertilized.
Source: Oren et al. 2001 Nature
A
A
E
E

18. Free Air Carbon Enrichment (FACE) Experiments
POPFACE : European FACE
Experiment on Poplar Plantations
Rhinelander, WI
Oak Ridge (ORNL) CO2 Enrichment
of Sweetgum
Duke University FACE – Loblolly Pine
Norby and Zak 2011
Tuscania, Italy

19. Duke Free Air Carbon Enrichment (FACE) Experiments
• Wind carries CO2 into the stand
• Elevated CO2 (ambient +200
ppm CO2).

20. Duke FACE: Elevated CO2
Sustained increases in biomass
production with CO2
Averaged 28% greater NPP in elevated
treatments
Source: McCarthy et al. 2010 New Phytologist

21. Duke FACE: Elevated CO2
Stand growth increased under
elevated CO2, but the extent is
dependent on soil fertility.
Source: McCarthy et al. 2010 New Phytologist

22. Oak Ridge (ORNL) Air Carbon Enrichment (FACE)
Experiments (L. styraciflua)
Elevated CO2
Ambient CO2
• Early large increase in NPP response to CO2
• Increased NPP was not sustained
• Soil N availability declined faster under elevated CO2
Source: Norby et al. 2010 PNAS

23. Forest Response to Elevated CO2
Median NPP stimulation of 23±2 %
Populus tremuloides
P. trem/B. papyrifera
P. alba
P. nigra
P. x euramericana
Pinus taeda
L. styraciflua
500 1000 1500 2000 2500
NPPa (g C m-2)
NPPe (g C m-2)
2500
2000
1500
1000
500
Source: Norby et al.2005 PNAS; Norby and Zak 2011
At high LAI,
enhancement
due to increased
light use
efficiency (i.e.
photosynthesis)
At low LAI,
enhancement due
to increased light
absorption

24. Will increasing atmospheric CO2 increase carbon
sequestration under all circumstances and/or alter carbon
cycling?
Biomass
550 ppm CO2 - Scenario I
Present
550 ppm CO2 - Scenario II
Increase Initial growth rate, carrying capacity, or both?
Groninger et al. 1999

25. Do forest use less water under
elevated CO2?
• Theory suggests that rising CO2 concentrations
should decrease stomatal conductance and reduce
forest water use.
• Direct effects of elevated CO2 on canopy or stand
water use are more difficult to assess.
• Data indicates that closed-canopy forests reduce
water use 4-11% under elevated CO2
• Response in younger stands is uncertain

26. Fecundity and Pest
Relationships
• Elevated CO2 increased seed production (Duke), flowering, and
seed mass, germination rate, and seedling vigor (Rhinelander).
• Resin production is important for
defense against bark beetles
• Duke FACE – increased elevated CO2
enhanced resin flow in loblolly pine
• Hypothesis: elevated CO2 increases photosynthesis more than
growth; therefore extra carbohydrate supply will be invested in
reproduction and defensive compounds
Source: Novick et al. 2012 Tree Phys.
Resin flow

27. Competitive
Relationships
• Species and genotypes express differences in the degree of
response to elevated CO2 that could affect competitive relationships.
• Base on a comparison of 18 FACE experiments, forest ecosystems
appear to be more responsive to CO2 than grassland ecosystems.
• Invasive species?
Source: Nowak et al. 2002

28. Summary of Elevated CO2 Research
• Rising atmospheric CO2 will likely
increase forest productivity in southern
forests
• The magnitude of this response will be
limited by resource availability
(nitrogen and water)
Biomass
550 ppm CO2 - Scenario I
Present
• Forest may use less water under certain conditions
• Competitive relationships?
• Increased carbohydrate availability under elevated CO2
may impart increased forest resilience:
– Increased production of secondary defensive compounds
– Increased fecundity
550 ppmCO2 - Scenario II
Time

29. Management Implications
• Should a forest manager base management decisions based on the certainty of rising CO2
concentrations? Probably not directly.
• Management decisions (e.g. species, genotypes, fertilization, weed control), environmental
variability, and disease will likely have a much larger impact on forest growth than elevated
CO2.
• However, the potential positive effects of CO2 should not be ignored.
– Forest process models suggest potential increases of 20% over the next 30 years from
elevated CO2
– Leverage CO2 fertilization effect through good silviculture
– Increase the efficiency of fertilizer use, primarily nitrogen
– Good weed control
– Maintain soil organic matter
– Utilize genetically improve seedlings (MCP, varietals)
Good Forest Management is Good Carbon Management

30. Resources
www.fs.usda.gov/ccrc/
www.taccimo.sgcp.ncsu.edu
www.pinemap.org
www.floridaclimateinstitute.org/
www.nc-climate.ncsu.edu/
www.seclimate.org/