Impact of Canopy Decoupling and Subcanopy Advection on the Annual Carbon Balance of a Boreal Scots Pine Forest as Derived From Eddy Covariance

Abstract. We analyzed the dynamics of carbon balance components: gross primary production (GPP) and total ecosystem respiration (TER), of a boreal Scots pine forest in Southern Finland. The main focus is on investigations of environmental drivers of GPP and TER and how they affect the inter-annual variation in the carbon balance in autumn (September–December). We used standard climate data and CO2 exchange measurements collected by the eddy covariance (EC) technique over 11 years. EC data revealed that increasing autumn temperature significantly enhances TER: the temperature sensitivity was 9.5 gC m−2 °C−1 for the period September–October (early autumn when high radiation levels still occur) and 3.8 gC m−2 °C−1 for November–December (late autumn with suppressed radiation level). The cumulative GPP was practically independent of the temperature in early autumn. In late autumn, air temperature could explain part of the variation in GPP but the temperature sensitivity was very weak, less than 1 gC m−2 °C−1. Two models, a stand photosynthesis model (COCA) and a global vegetation model (ORCHIDEE), were used for estimating stand GPP and its sensitivity to the temperature. The ORCHIDEE model was tested against the observations of GPP derived from EC data. The stand photosynthesis model COCA predicted that under a predescribed 3–6 °C temperature increase, the temperature sensitivity of 4–5 gC m−2 °C−1 in GPP may appear in early autumn. The analysis by the ORCHIDEE model revealed the model sensitivity to the temporal treatment of meteorological forcing. The model predictions were similar to observed ones when the site level 1/2-hourly time step was applied, but the results calculated by using daily meteorological forcing, interpolated to 1/2-hourly time step, were biased. This is due to the nonlinear relationship between the processes and the environmental factors.

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Peer review report 1 On “Biometric and eddy covariance-based assessment of decadal carbon sequestration of a temperate Scots pine forest”

Agricultural and Forest Meteorology ◽

10.1016/j.agrformet.2015.07.199 ◽

2015 ◽

Vol 201 ◽

pp. 524

Author(s):

Nobuko Saigusa

Keyword(s):

Carbon Sequestration ◽

Peer Review ◽

Eddy Covariance ◽

Scots Pine ◽

Pine Forest ◽

Scots Pine Forest

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Biometric and eddy covariance-based assessment of decadal carbon sequestration of a temperate Scots pine forest

Agricultural and Forest Meteorology ◽

10.1016/j.agrformet.2013.02.008 ◽

2013 ◽

Vol 174-175 ◽

pp. 135-143 ◽

Cited By ~ 30

Author(s):

B. Gielen ◽

B. De Vos ◽

M. Campioli ◽

J. Neirynck ◽

D. Papale ◽

...

Keyword(s):

Carbon Sequestration ◽

Eddy Covariance ◽

Scots Pine ◽

Pine Forest ◽

Scots Pine Forest

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Autumn warming and carbon balance of a boreal Scots pine forest in Southern Finland

Biogeosciences Discussions ◽

10.5194/bgd-6-7053-2009 ◽

2009 ◽

Vol 6 (4) ◽

pp. 7053-7081 ◽

Cited By ~ 3

Author(s):

T. Vesala ◽

S. Launiainen ◽

P. Kolari ◽

J. Pumpanen ◽

S. Sevanto ◽

...

Keyword(s):

Environmental Factors ◽

Scots Pine ◽

Temperature Sensitivity ◽

Carbon Balance ◽

Pine Forest ◽

Time Step ◽

Late Autumn ◽

Photosynthesis Model ◽

Early Autumn ◽

Scots Pine Forest

Abstract. We analyzed the dynamics of carbon balance components: gross primary production (GPP) and total ecosystem respiration (TER), of a boreal Scots pine forest in Southern Finland. Our aim was to study how these dynamics are related to different environmental conditions and how they affect the inter-annual variation in the carbon balance in autumn (September–December). We used standard micrometeorological data and CO2 exchange measurements collected by the eddy covariance (EC) technique over 11 years. The intra-annual relationships between the carbon balance components and the environmental factors were studied by the correlation analysis. Two models, a stand photosynthesis model and a generic dynamic vegetation model (ORCHIDEE), were also applied in the analysis. EC data revealed that increasing autumn temperature significantly enhances TER: the temperature sensitivity was 9.5 gC m−2 °C−1 for the period September–October (early autumn when high radiation levels still occur) and 3.8 gC m−2 °C−1 for November–December (late autumn with suppressed radiation level). The cumulative GPP was practically independent of the temperature in early autumn. In late autumn, air temperature could explain part of the variation in GPP but the temperature sensitivity was very weak, less than 1 g C m−2 °C−1. The stand photosynthesis model predicted that under a predescribed 3–6°C temperature increase, the temperature sensitivity of 4–5 gC m−2 °C−1 in GPP may appear in early autumn. The TER and GPP sensitivities, produced by the ORCHIDEE model, were similar to observed ones when the site level ½ h time step was applied, but the results calculated by using daily meteorological forcing, interpolated to ½ h time step, were biased stemming from the nonlinear relationship between the processes and the environmental factors.

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