Long-Term Carbon Dioxide Fluxes from a Very Tall Tower in a Northern Forest: Flux Measurement Methodology

Berger, Bradford W.; Davis, K. J.; Yi, Chuixiang; Bakwin, Peter S.; Zhao, C.

doi:10.1175/1520-0426(2001)018<0529:ltcdff>2.0.co;2

Cited by 139 publications

(106 citation statements)

References 39 publications

(39 reference statements)

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“…All three sites are part of the Chequamegon Ecosystem Atmosphere Study (ChEAS; http://cheas.psu.edu). The sites are also affiliated with the Ameri-Flux Network ) and measurements and processing are consistent with standard Ameri-Flux/Flux-Net protocols (Berger et al, 2001;Baldocchi, 2003). (Strack and Waddington, 2007 (Cook et.…”

Section: Site Descriptionsmentioning

confidence: 84%

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Contrasting carbon dioxide fluxes between a drying shrub wetland in Northern Wisconsin, USA, and nearby forests

et al. 2009

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Abstract. Wetland biogeochemistry is strongly influenced by water and temperature dynamics, and these interactions are currently poorly represented in ecosystem and climate models. A decline in water table of approximately 30 cm was observed at a wetland in Northern Wisconsin, USA over a period from 2001-2007, which was highly correlated with an increase in daily soil temperature variability. Eddy covariance measurements of carbon dioxide exchange were compared with measured CO 2 fluxes at two nearby forests in order to distinguish wetland effects from regional trends. As wetland water table declined, both ecosystem respiration and ecosystem production increased by over 20% at the wetland, while forest CO 2 fluxes had no significant trends. Net ecosystem exchange of carbon dioxide at the wetland was not correlated with water table, but wetland evapotranspiration decreased substantially as the water table declined. These results suggest that changes in hydrology may not have a large impact on shrub wetland carbon balance over inter-annual time scales due to opposing responses in both ecosystem respiration and productivity.

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Section: Site Descriptionsmentioning

confidence: 84%

“…Turbulent fluxes of momentum, heat, water vapour, and CO 2 were calculated at half-hourly intervals for all sites using the methodology described in Berger et al (2001), basically identical to that applied in Desai et. al.…”

Section: Flux Calculationmentioning

confidence: 99%

Contrasting carbon dioxide fluxes between a drying shrub wetland in Northern Wisconsin, USA, and nearby forests

et al. 2009

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“…These measurements are used to calibrate the fast-response infrared gas analyzers and to calculate the rate of change of storage for CO 2 (Davis et al, 2003). The eddy covariance instrumentation and methodology is described in detail in Berger et al (2001) and Davis et al (2003). Davis et al (2003) developed an algorithm for preferred NEE that combines measurements at the three levels to maintain a large footprint while avoiding the influence of the clearing around the tower.…”

Section: Eddy Covariance Flux Datamentioning

confidence: 99%

The imprint of surface fluxes and transport on variations in total column carbon dioxide

et al. 2012

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Abstract. New observations of the vertically integrated CO 2 mixing ratio, CO 2 , from ground-based remote sensing show that variations in CO 2 are primarily determined by large-scale flux patterns. They therefore provide fundamentally different information than observations made within the boundary layer, which reflect the combined influence of large-scale and local fluxes. Observations of both CO 2 and CO 2 concentrations in the free troposphere show that large-scale spatial gradients induce synoptic-scale temporal variations in CO 2 in the Northern Hemisphere midlatitudes through horizontal advection. Rather than obscure the signature of surface fluxes on atmospheric CO 2 , these synopticscale variations provide useful information that can be used to reveal the meridional flux distribution. We estimate the meridional gradient in CO 2 from covariations in CO 2 and potential temperature, θ, a dynamical tracer, on synoptic timescales to evaluate surface flux estimates commonly used in carbon cycle models. We find that simulations using Carnegie Ames Stanford Approach (CASA) biospheric fluxes underestimate both the CO 2 seasonal cycle amplitude throughout the Northern Hemisphere midlatitudes and the meridional gradient during the growing season. Simulations using CASA net ecosystem exchange (NEE) with increased and phase-shifted boreal fluxes better fit the observations. Our simulations suggest that climatological mean CASA fluxes underestimate boreal growing season NEE (between 45-65 • N) by ∼40 %. We describe the implications for this large seasonal exchange on inference of the net Northern Hemisphere terrestrial carbon sink.

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“…However, with a careful system design and the correct field installation, most errors are generally small. Based upon our own experience, errors related to gas analyzer calibration and signal dampening in tubes are both typically within 2-3 %, while errors due to sensor separation are less than 2 % (Berger et al, 2001). Errors in EC measurements are generally considered to be less than 7 % during daytime and less than 12 % during nighttime as summarized by Baldocchi (2003).…”

Section: Approach 1: Quantification Of the Nee By Eddy Covariancementioning

confidence: 99%

A fertile peatland forest does not constitute a major greenhouse gas sink

et al. 2013

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Abstract. Afforestation has been proposed as a strategy to mitigate the often high greenhouse gas (GHG) emissions from agricultural soils with high organic matter content. However, the carbon dioxide (CO 2 ) and nitrous oxide (N 2 O) fluxes after afforestation can be considerable, depending predominantly on site drainage and nutrient availability. Studies on the full GHG budget of afforested organic soils are scarce and hampered by the uncertainties associated with methodology. In this study we determined the GHG budget of a spruce-dominated forest on a drained organic soil with an agricultural history. Two different approaches for determining the net ecosystem CO 2 exchange (NEE) were applied, for the year 2008, one direct (eddy covariance) and the other indirect (analyzing the different components of the GHG budget), so that uncertainties in each method could be evaluated. The annual tree production in 2008 was 8.3 ± 3.9 t C ha −1 yr −1 due to the high levels of soil nutrients, the favorable climatic conditions and the fact that the forest was probably in its phase of maximum C assimilation or shortly past it. The N 2 O fluxes were determined by the closed-chamber technique and amounted to 0.9 ± 0.8 t C eq ha −1 yr −1 . According to the direct measurements from the eddy covariance technique, the site acts as a minor GHG sink of −1.2 ± 0.8 t C eq ha −1 yr −1 . This contrasts with the NEE estimate derived from the indirect approach which suggests that the site is a net GHG emitter of 0.6 ± 4.5 t C eq ha −1 yr −1 . Irrespective of the approach applied, the soil CO 2 effluxes counter large amounts of the C sequestration by trees. Due to accumulated uncertainties involved in the indirect approach, the direct approach is considered the more reliable tool. As the rate of C sequestration will likely decrease with forest age, the site will probably become a GHG source once again as the trees do not compensate for the soil C and N losses. Also forests in younger age stages have been shown to have lower C assimilation rates; thus, the overall GHG sink potential of this afforested nutrient-rich organic soil is probably limited to the short period of maximum C assimilation.

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Long-Term Carbon Dioxide Fluxes from a Very Tall Tower in a Northern Forest: Flux Measurement Methodology

Cited by 139 publications

References 39 publications

Contrasting carbon dioxide fluxes between a drying shrub wetland in Northern Wisconsin, USA, and nearby forests

Contrasting carbon dioxide fluxes between a drying shrub wetland in Northern Wisconsin, USA, and nearby forests

The imprint of surface fluxes and transport on variations in total column carbon dioxide

A fertile peatland forest does not constitute a major greenhouse gas sink

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