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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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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


Interannual variation from diurnal to annual time scale in the northern America.

variability

in the rate of

accumulation

of atmospheric

CO2


Issues variation from diurnal to annual time scale in the northern America.

  • 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 variation from diurnal to annual time scale in the northern America.(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.


Respiration and temperature variation from diurnal to annual time scale in the northern America.

Northern OBS tower (NB)

Manitoba, Canada

Wofsy, Munger et al.

Boreal black spruce forest


Respiration and variation from diurnal to annual time scale in the northern America.

temperature

WLEF TV tower (WL)

Northern Wisconsin, USA

Davis, Bakwin et al.

Mixed forest/wetland mosaic


Respiration and variation from diurnal to annual time scale in the northern America.

temperature

Harvard Forest (HF)

Massachusetts, USA

Wofsy, Munger et al.

Deciduous forest


Respiration and variation from diurnal to annual time scale in the northern America.

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).


Soil carbon pool on annual time scales?

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


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


Season though temperature is similar between these two seasons.

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 though temperature is similar between these two seasons.(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.


NEE and precipitation though temperature is similar between these two seasons.

Northern OBS tower (NB)

Manitoba, Canada

Wofsy, Munger et al.

Boreal black spruce forest


NEE and precipitation though temperature is similar between these two seasons.

WLEF TV tower (WL)

Northern Wisconsin, USA

Davis, Bakwin et al.

Mixed forest/wetland mosaic


NEE and precipitation though temperature is similar between these two seasons.

Harvard Forest (HF)

Massachusetts, USA

Wofsy, Munger et al.

Deciduous forest


NEE and precipitation though temperature is similar between these two seasons.

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 though temperature is similar between these two seasons.(NB, WB, WL, HF)

NEE and net radiation

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


NEE and net radiation though temperature is similar between these two seasons.

Northern OBS tower (NB)

Manitoba, Canada

Wofsy, Munger et al.

Boreal black spruce forest


NEE and net radiation though temperature is similar between these two seasons.

WLEF TV tower (WL)

Northern Wisconsin, USA

Davis, Bakwin et al.

Mixed forest/wetland mosaic


NEE and net radiation though temperature is similar between these two seasons.

Harvard Forest (HF)

Massachusetts, USA

Wofsy, Munger et al.

Deciduous forest


NEE and net radiation though temperature is similar between these two seasons.

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 though temperature is similar between these two seasons.(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.


NEE and PAR though temperature is similar between these two seasons.

Northern OBS tower (NB)

Manitoba, Canada

Wofsy, Munger et al.

Boreal black spruce forest


NEE and PAR though temperature is similar between these two seasons.

WLEF TV tower (WL)

Northern Wisconsin, USA

Davis, Bakwin et al.

Mixed forest/wetland mosaic


NEE and PAR though temperature is similar between these two seasons.

Harvard Forest (HF)

Massachusetts, USA

Wofsy, Munger et al.

Deciduous forest


NEE and PAR though temperature is similar between these two seasons.

Walker Branch tower (WB)

Baldocchi, Wilson et al.

Tennessee, USA

Deciduous forest


Summary
Summary though temperature is similar between these two seasons.

  • 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.


Discontinuous permafrost exists though temperature is similar between these two seasons.

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


Across many sites though temperature is similar between these two seasons.

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)


Acknowledgements though temperature is similar between these two seasons.

  • 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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