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C. Yi, K.J. Davis, The Penn State University P.S. Bakwin, NOAA/CMDL - PowerPoint PPT Presentation


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The observed responses of ecosystem CO2 exchange to climate variation from diurnal to annual time scale in the northern America. C. Yi, K.J. Davis, The Penn State University P.S. Bakwin, NOAA/CMDL T. Zhou, Beijing Normal University D.D. Baldocchi and colleagues, UC Berkeley

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slide1

The observed responses of ecosystem CO2 exchange to climate variation from diurnal to annual time scale in the northern America.

C. Yi, K.J. Davis, The Penn State University

P.S. Bakwin, NOAA/CMDL

T. Zhou, Beijing Normal University

D.D. Baldocchi and colleagues, UC Berkeley

S. Wofsy and colleagues, Harvard University

slide3

Interannual

variability

in the rate of

accumulation

of atmospheric

CO2

slide4

Issues

  • What climatic factors control the interannual variability in NEE?
part i climate variables and nee at various time scales nb wb wl hf
Part I: Climate variables and NEE at various time scales(NB, WB, WL, HF)

Respiration and temperature

Correlation between nighttime tower flux and air temperature is very high on daily, monthly and seasonal time scales.

Correlation breaks down on interannual scales.

slide6

Respiration and temperature

Northern OBS tower (NB)

Manitoba, Canada

Wofsy, Munger et al.

Boreal black spruce forest

slide7

Respiration and

temperature

WLEF TV tower (WL)

Northern Wisconsin, USA

Davis, Bakwin et al.

Mixed forest/wetland mosaic

slide8

Respiration and

temperature

Harvard Forest (HF)

Massachusetts, USA

Wofsy, Munger et al.

Deciduous forest

slide9

Respiration and

temperature

Walker Branch tower (WB)

Baldocchi, Wilson et al.

Tennessee, USA

Deciduous forest

why does the temperature respiration relationship break down on annual time scales
Why does the temperature-respiration relationship break down on annual time scales?

Hypotheses:

  • Annual respiration is proportional to annual litter production which is a weak function of temperature?
  • Temperature sensitivity is limited at the seasonal extremes (summer, winter).
slide11

Soil carbon pool

Soil respiration Litter production (Ta, P, Rn, fertilizer, …)

slide12

Respiration in autumn is much higher than in spring even though temperature is similar between these two seasons.

slide13

Season

NB

B R2T

WL

B R2T

HV

B R2T

WB

B R2T

Spring

0.0351 0.47 -5.1

0.0844 0.50 5.2

0.0445 0.38 5.1

0.0632 0.60 13.3

Summer

0.0676 0.36 13.3

0.0526 0.23 16.2

0.0255 0.08 17.0

0.0283 0.10 22.3

Autumn

0.0603 0.83 -1.3

0.0801 0.45 7.8

0.0231 0.18 8.0

0.0547 0.66 14.1

Winter

0.0126 0.08 -21.8

0.0142 0.04 -7.0

0.0283 0.08 -3.3

0.0340 0.46 4.4

Seasonal distribution of temperature sensitivity B, (Re=AeBT ).

Spring B is the largest except at the NB site.

There is no correlation between T and respiration in winter except at the WB site.

climate variables and nee at various time scales nb wb wl hf
Climate variables and NEE at various time scales(NB, WB, WL, HF)

NEE of CO2 and precipitation

Correlation between NEE and precipitation is very poor on daily, monthly and seasonal time scales.

Correlation becomes strong for interannual time scales.

slide15

NEE and precipitation

Northern OBS tower (NB)

Manitoba, Canada

Wofsy, Munger et al.

Boreal black spruce forest

slide16

NEE and precipitation

WLEF TV tower (WL)

Northern Wisconsin, USA

Davis, Bakwin et al.

Mixed forest/wetland mosaic

slide17

NEE and precipitation

Harvard Forest (HF)

Massachusetts, USA

Wofsy, Munger et al.

Deciduous forest

slide18

NEE and precipitation

Walker Branch tower (WB)

Baldocchi, Wilson et al.

Tennessee, USA

Deciduous forest

climate variables and nee at various time scales nb wb wl hf1
Climate variables and NEE at various time scales(NB, WB, WL, HF)

NEE and net radiation

Correlation between NEE and net radiation is strong on all time scales.

slide20

NEE and net radiation

Northern OBS tower (NB)

Manitoba, Canada

Wofsy, Munger et al.

Boreal black spruce forest

slide21

NEE and net radiation

WLEF TV tower (WL)

Northern Wisconsin, USA

Davis, Bakwin et al.

Mixed forest/wetland mosaic

slide22

NEE and net radiation

Harvard Forest (HF)

Massachusetts, USA

Wofsy, Munger et al.

Deciduous forest

slide23

NEE and net radiation

Walker Branch tower (WB)

Baldocchi, Wilson et al.

Tennessee, USA

Deciduous forest

climate variables and nee at various time scales nb wb wl hf2
Climate variables and NEE at various time scales(NB, WB, WL, HF)

NEE and PAR

Correlation between NEE and PAR is good on short time scales, and becomes worse on annual time scale.

slide25

NEE and PAR

Northern OBS tower (NB)

Manitoba, Canada

Wofsy, Munger et al.

Boreal black spruce forest

slide26

NEE and PAR

WLEF TV tower (WL)

Northern Wisconsin, USA

Davis, Bakwin et al.

Mixed forest/wetland mosaic

slide27

NEE and PAR

Harvard Forest (HF)

Massachusetts, USA

Wofsy, Munger et al.

Deciduous forest

slide28

NEE and PAR

Walker Branch tower (WB)

Baldocchi, Wilson et al.

Tennessee, USA

Deciduous forest

summary
Summary
  • Dependence of NEE on climatic factors is not consistent across time scales.
  • Net radiation and precipitation become more correlated with NEE on annual time scale.
  • Dryness=Rn/(L*P) may be used as an annual controlling parameter on interannual variability of NEE of CO2.
slide30

Discontinuous permafrost exists

Water stress is not critical

Soil thaw is critical; this depends on Rn

Drought leads to more release of CO2

With abundant soil moisture, available energy is critical for CO2 uptake.

As dryness>0.95, water stress becomes critical.

1998 is the second year of drought. 1999 is the third year of drought. (?)

Drought has strong effect on interannual variability in NEE at WB.

NB

WL

HV

WB

slide31

Across many sites

Average per site over several years

HV-Harvard Forest (US,92-99)

TH-Tharandt (Germany, 97-99)

WL-WLEF (US, 97-99)

WB-Walker Branch (US,95-98)

NO-Norunda (Sweden,96-97)

LW-Little Washita (US,97-98)

LO-Loobos (Netherlands,97-98)

HL-Howland (US, 96-97)

HE-Hesse (France, 98-99)

slide32

Acknowledgements

  • Funding and personnel support:
    • DoE – NIGEC – Midwest and Great Plains
    • NOAA CMDL
    • NASA – EOS Validation
    • DoE – TCP/TECO
    • NSF/NCAR
    • USDA-FS
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