landscape-level (eddy covariance) measurement of co 2 and other fluxes measuring components of solar...
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Landscape-level
(Eddy Covariance)
Measurement of CO2
and Other Fluxes
Measuring Componentsof Solar Radiation
Close-up ofEddy Covariance
Flux Sensors
Tower Flux Measurement and Analysis
Verma/IndoFlux/IndoFlux_July 2006
Outline• Background information/
methodology
• Flux magnitudes: seasonal/ interannual variations
• Controlling variables
• Comments
Objectives• Quantify CO2 exchange in major
ecosystems: seasonal and interannual variability
• Improve our basic understanding of biophysical processes that govern CO2 exchange in these ecosystems
• Test and improve terrestrial biosphere models of CO2, water, and energy exchange
Landscape Level Carbon Dioxide Flux(uptake and release)
Plant photosynthesis
Above ground productivity
Root and rhizosphererespiration
Partitioning of Carbon in Agroecosystems
Soil respiration
Plant respiration
Microbialrespiration
Root exudates
Root productivity
Organicmatter
decomposition
Methodology: Eddy Covariance
Fluxes of CO2, Water Vapor, and Energy:
• Continuous Measurements
• Long-term
• Ecosystem scale/landscape level
ppm
m /s
1.5
15
3qc
w
5
1200
Instantaneous F lux = ws M ean H ourly F lux = Tim e average of
1201 1202 1203 1204 1205
Td
g/kg
Eddy Covariance
instantaneous flux = wsfor C Ofor w ater vaporfor sensib le heat
2for C Ofor w ater vaporfor sensib le heat
2
Mead, Nebraska
• Primary Measurements- Fluxes of CO2, water vapor, sensible heat & momentum- Mean wind speed, air temperature, humidity and CO2
concentration- Wind direction- Soil heat flux & soil temperature- Radiation:
Net radiation Short wave radiation (incoming & reflected) PAR (incoming & reflected)
- Light interception- Atmospheric pressure- Precipitation
• Supporting Measurements- Soil moisture- Leaf area index, canopy height, biomass- Leaf nitrogen content
Measurements
Data Submission
Tower Eddy Covariance CO2 Flux Measurements: Net Ecosystem Exchange (NEE)
Mead, Nebraska
-10
-5
0
5
10
15
20
25
5/1/01 8/29/01 12/27/01 4/26/02 8/24/02 12/22/02 4/21/03 8/19/03 12/17/03 4/15/04 8/13/04 12/11/04 4/10/05
Dai
ly N
EE
(g
C m
-2 d
-1)
Site 1
P HHH PP
maize maize maize
Irrigated Continuous
Maize
maize
P H
-10
-5
0
5
10
15
20
25
5/1/01 8/29/01 12/27/01 4/26/02 8/24/02 12/22/02 4/21/03 8/19/03 12/17/03 4/15/04 8/13/04 12/11/04 4/10/05
Dai
ly N
EE
(g
C m
-2 d
-1)
Site 2
P P P HHH
maize maizesoybean
IrrigatedMaize-Soybean
Rotation
soybean
P
H
-10
-5
0
5
10
15
20
25
5/1/01 8/29/01 12/27/01 4/26/02 8/24/02 12/22/02 4/21/03 8/19/03 12/17/03 4/15/04 8/13/04 12/11/04 4/10/05
Dai
ly N
EE
(g
C m
-2 d
-1)
Site 3
P P PH H H
maizemaize soybean
RainfedMaize-Soybean
Rotation
soybean
P
H
Daytime CO2 Uptake and Night Emissions
Ecosystem
Peak daytime
CO2 uptake
(mg m-2s-1)
Peak night
CO2 emission
(mg m-2s-1)
Leaf Area Index
(LAI)
Irrigated maize 2.8 – 3.0 0.6 – 0.7 5.6 – 6.0
Rainfed maize 2.6 0.4 – 0.5 4.0
Irrigated soybean 1.7 0.7 5.7
Rainfed soybean 1.5 0.4 3.0
Grassland (tallgrass prairie)
1.2 0.4 – 0.5 3.0
Temperate forest 0.9 0.2 – 0.3 4.9
Reday = NEEnight * Q 10 (Ta,day - Ta,night)/10
GPP = NEE - Re
Ecosystem Respiration (Re) and Gross Primary Productivity (GPP)
Annually Integrated NEE
(g C m-2 y-1)Maize, NE 300 to 500 (Verma et al., 2005)
Harvard Forest, MA 200 (Barford et al., 2003)
Howland Forest, ME 174 (Hollinger et al., 2004)
Univ. of Michigan Biological St 80 to 170 (Schmid et al., 2003)
Wind River, WA -50 to 200 (Pers. Comm.)
Douglas Fir, B.C. 270 to 420 (Morgenstern et al., 2004)
Tallgrass Prairie, OK 50 to 275 (Suyker et al., 2003)
Northern Temperate Grassland, Alberta
-18 to 20 (Flanagan et al., 2002)
Mediterranean, Annual Grassland, CA
-30 to 130 (Xu and Baldocchi, 2003)
Soybean, NE -10 to -75 (Verma et al., 2005)
4.0
-1.0
0.0
1.0
2.0
3.0
0 500 1000 1500 2000
Incoming PAR (mol m-2 s-1)
NE
E (
mg
m-2
s-1
)
June 13-19: V6-V7: 0.4<LAI<1.3
July 4-10: V11-V12: 4.4<LAI<5.6
July 18-24: V19-VT: 6.2<LAI<6.3
Aug 29-Sept 4: R5: 3.7<LAI<4.3
Daytime CO2 Flux Irrigated Maize
Night CO2 Flux
Tallgrass Prairie, Manhattan, KS, 1987
Energy Partitioning
Daytime
Energy Partitioning
Tallgrass Prairie7/31/97
-500
-250
0
250
500
750
0 600 1200 1800 2400
Local Time, Hrs
Flu
x, W
m-2
RnGHLE
Shidler, Oklahoma
Tallgrass Prairie, Manhattan, KS, 1987
Checks and Balances• Data Quality Control
– Foken and Wichura, 1996, Agric. For. Meteorol., 78, 83-105
– Aubinet et al., 2000, Advances in Ecol. Res., 30, 113-175
• Energy Budget Closure: LE + H vs. Rn + G
• NEE – Biomass Relationship
Day Night
NEEday NEEnight
Rg Rr Rc
Daily net gain of CO2 by crop
Rg Rr
Rc
Gain of CO2 by cropduring day
= NEEday – RgdayD
D
=Net canopy photosynthesis
in 24 hours
= ( NEEday + NEEnight ) – ( Rgday + Rg night ) D
N
= Daily NEE + Daily Rg
Loss of CO2 by cropat night
= Rc + Rr
= NEEnight – Rg night N
N
N
D
N
=( NEEday – Rgday) + ( NEEnight – Rg night )
DD
N
N
N Rc + Rr + Rg = NEEnight
(Biscoe et al; 1975. J. Applied Ecology, 12, 269-291)
NEE-Biomass Relationship
Daily net gain of CO2 by crop = Daily NEE + Daily Rg
(Biscoe et al., 1975, J. Applied Ecology, 12, 269-291)
NEE = Net ecosystem CO2 exchangeRg = Respiration by soil organisms
Estimating Microbial Respiration (Rg)
• Soil surface CO2 flux measurements (Fs)– Two different kinds of chambers:
Model LI-6200, Li-Cor, Lincoln, NEHutchinson & Mosier (1981) type chamber
– Used data from field measurements of maize soil respiration in root excluded and non-root excluded soil to estimate Rg
• Night NEE data– Adjusted for plant respiration based on leaf gas
exchange measurements– Adjusted for night/day temperatures– Applied measurements of root-excluded vs. non-root
excluded soil to estimate Rg as mentioned above
Challenges• Insufficient mixing at night
• Filling in data gaps
• Complex terrain
N2O and CH4 Fluxes
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