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Eddy covariance - estimating ecosystem fluxes of carbon and water Asko Noormets, Jiquan Chen Dept. Earth, Ecological and Environmental Sciences The University of Toledo Ge Sun, Steve McNulty Southern Global Change Program, USDA FS

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Eddy covariance - estimating ecosystem fluxes of carbon and water Asko Noormets, Jiquan Chen Dept. Earth, Ecological and Environmental Sciences The University of Toledo Ge Sun, Steve McNulty Southern Global Change Program, USDA FS. Outline. Background - brief theory and history - PowerPoint PPT Presentation

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Page 1: Outline

Eddy covariance - estimating ecosystem fluxes of

carbon and water

Asko Noormets, Jiquan ChenDept. Earth, Ecological and Environmental Sciences

The University of Toledo

Ge Sun, Steve McNultySouthern Global Change Program, USDA FS

Page 2: Outline

Outline

1. Background - brief theory and history

2. What does it look like?

3. Carbon flux in a managed landscape

4. Significance

Page 3: Outline

Principle of operation

• 3-D wind speed and direction• CO2 and H2O concentration

How do they co-vary

GEP + R = NEE ?

day day & night

Page 4: Outline

Co-variance

-0.6

-0.3

0

0.3

0.6

12:21:45 12:21:46 12:21:48 12:21:50 12:21:52 12:21:53 12:21:55 12:21:57 12:21:58 12:22:00 12:22:02

u(z),

m s-1

583

583.75

584.5

585.25

586

[CO2], mg m

-3

Page 5: Outline

Theory

Page 6: Outline

History (Baldocchi 2003 GCB)

Theoretical framework - Sir Osborne Reynolds (1895)

First application - Scrase (1930), momentum transfer, analog instruments Also later, post WW II experiments, mostly focused on measuring the turbulent structure of atmospheric boundary layer rather than CO2 exchange.

First measurements of CO2 flux - Desjardins & Lemon (1974)

First measurements over forests - Baumgartner (1969), Denmead (1969), Jarvis (1976)

First application of open-path IRGA-s and sonic anemometers for CO2 flux measurements - Anderson et al. (1984), Anderson & Verma (1986), Ohtaki (1984), Desjardins (1985)

First yearlong study - Wofsy et al. (1993), started in 1990Flux measurement networks - Fluxnet, Ameriflux, CarboEuroflux etc.Current questions - sources of interannual variation, winter fluxes, separating

contribution from layers, separating soil heterotrophic and autotrophic R.

Page 7: Outline
Page 8: Outline
Page 9: Outline
Page 10: Outline
Page 11: Outline

Ecosystem C fluxes

-20

-10

0

10

4/24 6/13 8/2 9/21 11/10 12/30 2/18 4/9Date

Fc (g

CO

2 m-2 d

-1)

NEE – net ecosystem exchange of carbonR – ecosystem respirationGEP – gross ecosystem productivity

Page 12: Outline

Seasonal course - NEE, R, GEP

-250

-200

-150

-100

-50

0

50

100

150May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr

NE

E (

g C

m-2

mo

-1)

MHWMRPPBCCYMP

0

50

100

150

200

250

May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr

R (

g C

m-2

mo

-1)

-500-450-400-350-300-250-200-150-100

-500

May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr

GE

P (

g C

m-2

mo

-1)

NEE – net ecosystem exchangeR – ecosystem respirationGEP – gross ecosystem productivity

Page 13: Outline

Decomposing NEE

0

0.5

1

1.5

May Jun Jul Aug Sep

SRR/

R

-1

-0.5

0

0.5

1May Jun Jul Aug Sep

NEE/

GEP

MHWMRPPBCCYMP -2

-1.5

-1

-0.5

0May Jun Jul Aug Sep

R/GE

P

Page 14: Outline

Age effect on light response of GEP

-12

-6

0

60 20 40 60 80

-12

-6

0

60 20 40 60 80

PAR (mol m-2 d-1)PAR (mol m-2 d-1)

GEP

(g C

O2 m

-2 d

-1)

Mixed hardwood3 years & 63 years

Red pine8 years & 65 years

Page 15: Outline

Regression of residuals of AQ response

-2

-1

0

1

2

3

0 1 2 3

MHWMRPPBCCYMP

VPD (kPa)Res

id. (

µmol

CO

2 m-2 s-1

)

-4-202468

10

-100 0 100 200 300 400

MHWMRPPBCCYMP

Hs (W m-2 d-1)

Res

id. (

µmol

CO

2 m-2 s-1

)

Page 16: Outline

Significance• Narrows error margins for ecosystem C balance

estimates (“missing carbon”).

• Sensitivity analysis of fluxes to environmental drivers. Differences in magnitude and seasonality.

• Due to being a spatially integrative technique (footprint), it can be linked to RS, and used to model exchange in larger scales.

• Quantitation of anthropogenic effects.

Page 17: Outline