carl j. bernacchi steven e. hollinger illinois state water survey, champaign, il tilden p. meyers
DESCRIPTION
Carbon Budget of Mature No-till Corn/Soybean Ecosystem in the North Central Region of the United States. Carl J. Bernacchi Steven E. Hollinger Illinois State Water Survey, Champaign, IL Tilden P. Meyers NOAA Atmospheric Turbulence Diffusion Division, Oak Ridge, Tennessee. - PowerPoint PPT PresentationTRANSCRIPT
Carbon Budget of Mature No-till Corn/Soybean Ecosystem in the
North Central Region of the United States
Carl J. Bernacchi
Steven E. HollingerIllinois State Water Survey, Champaign, IL
Tilden P. MeyersNOAA Atmospheric Turbulence Diffusion Division, Oak Ridge,
Tennessee
DEPARTMENT OF
I L L I N O I S
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Why Corn and Soybean?
Agricultural Land and C-sequestration
• Soils of native prairie were high in Soil Organic Carbon (SOC)
• Only ~40% of SOC still remains
• Can we increase SOC in the soils of Midwestern agriculture?
Donigian, et al. (1994), U.S.EPA, Athens, GA
Lal, R., 2004, Science, 304, 1623-1627
Rising Atmospheric CO2
• Controlling atmospheric CO2 is the focus of domestic and international efforts– Improvements in energy
• More efficient technology
• Improved fuels
– Kyoto protocol• Sequester C
• Sell C-credits
Focus on No-till
• No-till farming has many benefits– Lower costs– Minimize erosion– Better soil moisture– More pest predators, earth worms– Higher SOC (?)
Measuring SOC
• Soil measurements and models are traditionally used, but:– Soil measurements are prone to uncertainties
over time and space– Models require validation
• Augment the wealth of soil measurements / models with a different technique
Using Eddy Covariance to Estimate C Sequestration
• Eddy Covariance is a method in which fluxes of CO2, water, and energy can be measured directly
• Measurements represent a large area
• Measurements are made continuously throughout the year
CO2 fluxes to measure NEE
• Net Ecosystem Exchange = net total amount of C transferred between the atmosphere and an ecosystem over a given period of time
• Pn = Net photosynthesis
• Ra = Autotrophic Respiration
• Rh = Heterotrophic Respiration
n a hNEE P R R
Bondville Ameriflux Tower
Experimental Method
• 6 years of continuous eddy covariance measurements
• Corn/soybean rotation agro-ecosystem– 3 years of corn data– 3 years of soybean data– 3 complete rotation cycles
• Data collected and back-filled (modeled) as needed
Carbon Sequestration Potential
• If the amount of CO2 ENTERING the ecosystem is greater than the amount of CO2 LEAVING the system, then carbon is being sequestered
NEE over Six Years
1997 1998 1999 2000 2001 2002 2003Y ear
-30.0
-20.0
-10.0
0.0
10.0
NE
E (
mo
l C m
-2 d
-1)
C orn Soybean C orn Soybean C orn Soybean
Local C Fluxes
1997 1998 1999 2000 2001 2002 2003Y ear
-20.0
-15.0
-10.0
-5 .0
0.0
5.0
Cu
mm
ula
tive
NE
E (
me
tric
ton
s/h
a)
Large C-Sink, however…
• A large amount of C is removed from the field (yield)
• 100% of grain C is consumed annually
• Does yield explain all of this sink?
How much C is removed from the no-tilled field?
1997 1998 1999 2000 2001 2002 2003Y ear
-20.0
-15.0
-10.0
-5 .0
0.0
5.0
Cu
mm
ula
tive
NE
E (
me
tric
ton
s/h
a)
Regional C sink assessment• An Intensive Campaign (NACP) has been
proposed to do the most comprehensive C budget ever for a certain region of the U.S.
• Midwest defined as an ideal location– Relatively few urban areas– Single ecosystem type dominates
• A Regional Intensive Campaign requires as much information as possible for each ecosystem type
Regional C Budget
• Here in the Midwest, a large amount of C is fixed into grain
• The grain is removed from the field
• 100% of grain harvest is utilized
• Only ~20% of the total grain consumption occurs in the Midwest
Assessing the Regional C Budget
• Have– Three years of NEE
data for corn, soybean
– Precise yield data for these years on the exact field
– Yield data for each state in the U.S.
– Grain consumption statistics
• Need– NEE data for all states
• Assumptions– Our field is
representative of all fields
Ecosystem Harvest Index (EHI)
• Grain carbon (Cgr) was measured via combine yield monitors
• Growing season NEE (NEEg) was measured using eddy covariance
• EHI was then used as a proxy for NEE over the whole Midwest
gr
g
CEHI
NEE
grg
CNEE
EHI
Midwestern Carbon Fluxes (MMT)
C Fluxes (MMT) Maize Soybean Total
Growing season -154.7 -59.3 -214
Fallow season 49.5 65.0 114.5
Midwest Consumption 13.9 4.3 18.2
Net Midwest -91.3 10.0 -81.3
Regional C sink assessment
1997 1998 1999 2000 2001 2002 2003Y ear
-20.0
-15.0
-10.0
-5 .0
0.0
5.0
Cu
mm
ula
tive
NE
E (
me
tric
ton
s/h
a)
Conclusions
• Locally, Midwestern corn/soybean ecosystem represents a large C-sink to the atmosphere
• Globally, most of the C-sink is found in grain– Accounting for all Grain C, ecosystem is still a
sink (C sequestration potential exists)
Conclusions (cont’)
• Regionally, a huge C sink exists– Most C stored in grain is consumed out of the
region
– Over 81 MMT of C is fixed in this region
Acknowledgements• Office of Science (BER), U.S. Department
of Energy, Grant No DE-FG02-03ER63685
• National Oceanic and Atmospheric Association (NOAA)
• John Reifsteck
DEPARTMENT OF
I L L I N O I S
NAT URALRESOURCES
I l l i n o i s S t a t eSURVEY