Vegetation effects on the isotope composition of oxygen in atmospheric CO2

Farquhar, Graham D.; Lloyd, J.; Taylor, John A.; Flanagan, Lawrence B.; Syvertsen, James P.; Hubick, Kerry T.; Wong, Sherman; Ehleringer, James R.

doi:10.1038/363439a0

Cited by 393 publications

(410 citation statements)

References 22 publications

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“…All the models, except the Ball-Berry explained more than 50% of the variations in measured A. The hybrid, Leuning, and Farquhar models as well as the Farquhar et al (1993) version of the Cowan-Farquhar model had the lowest RMSE when contrasted with the other models.…”

Section: Model Assessment With Independent Parametersmentioning

confidence: 95%

“…Hence, the WUE approximation leads to a linear dependence of C i /C a on D. In Farquhar et al (1993) and Lloyd & Farquhar (1994), it was suggested that coupling the Cowan-Farquhar approximation of constant ∂E/∂A with a linearized relationship between carboxylation efficiency and C i leads to (3b) which leads to C i /C a µ rather than linear, and G is the leaf CO 2 compensation point.…”

Section: The Norman Modelmentioning

confidence: 99%

“…Interestingly, Norman's constant C i /C a model, the hybrid approach, and the Leuning models all yielded the lowest RMSE in this case despite differences in the closure assumptions (Table 1). Additionally, the Farquhar et al (1993) version of the Cowan-Farquhar model is a major improvement over the constant water use efficiency approximation. This improvement, in part, is due to the fact that C i /C a a D in the constant WUE approach whereas the Farquhar et al (1993) Modelling assimilation and intercellular CO 2 from measured conductance 1321 version leads to C i /C a a ÷D thereby reducing the sensitivity of modelled A on D, analogous to Norman's model.…”

Section: Model Assessment With Independent Parametersmentioning

confidence: 99%

“…For the Farquhar et al (1993) version of the model, l cf can also be estimated from d 13 C measured and using…”

Section: Cowan-farquhar Modelmentioning

confidence: 99%

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Modelling assimilation and intercellular CO₂ from measured conductance: a synthesis of approaches

Katul

Ellsworth

Lai

2000

Plant Cell & Environment

145

129

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A spectrum of models that estimate assimilation rate A from intercellular carbon dioxide concentration (Ci) and measured stomatal conductance to CO2 (gc) were investigated using leaf‐level gas exchange measurements. The gas exchange measurements were performed in a uniform loblolly pine stand (Pinus taeda L.) using the Free Air CO2 Enrichment (FACE) facility under ambient and elevated atmospheric CO2 for 3 years. These measurements were also used to test a newly proposed framework that combines basic properties of the A–Ci curve with a Fickian diffusion transport model to predict the relationship between Ci/Ca and gc, where Ca is atmospheric carbon dioxide concentration. The widely used Ball–Berry model and five other models as well as the biochemical model proposed by Farquhar et al. (1980) were also reformulated to express variations in Ci/Ca as a function of their corresponding driving mechanisms. To assess the predictive capabilities of these approaches, their respective parameters were estimated from independent measurements of long‐term stable carbon isotope determinations (δ13C), meteorological variables, and ensemble A–Ci curves. All eight approaches reproduced the measured A reasonably well, in an ensemble sense, from measured water vapour conductance and modeled Ci/Ca. However, the scatter in the instantaneous A estimates was sufficiently large for both ambient and elevated Ca to suggest that other transient processes were not explicitly resolved by all eight parameterizations. An important finding from our analysis is that added physiological complexity in modeling Ci/Ca (when gc is known) need not always translate to increased accuracy in predicting A. Finally, the broader utility of these approaches to estimate assimilation and net ecosystem exchange is discussed in relation to elevated atmospheric CO2.

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Section: Model Assessment With Independent Parametersmentioning

confidence: 95%

Section: The Norman Modelmentioning

confidence: 99%

Section: Model Assessment With Independent Parametersmentioning

confidence: 99%

“…For the Farquhar et al (1993) version of the model, l cf can also be estimated from d 13 C measured and using…”

Section: Cowan-farquhar Modelmentioning

confidence: 99%

See 2 more Smart Citations

Modelling assimilation and intercellular CO₂ from measured conductance: a synthesis of approaches

Katul

Ellsworth

Lai

2000

Plant Cell & Environment

145

129

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“…For example, with data on the various isotopes of C in the atmosphere and soil [e.g., Perruchoud et al, 1999;Trumbore, 1993;Trumbore et al, 1995;Van Dam et al, 1997;Wang et al, 1999, Ciais et al, 1995Francey et al, 1995;Bird et al, 1996;Keeling et al, 1996;Bernoux et al, 1998;Randerson et al, 1998;Ciais et al, 1999] and by 18 O measurements of atmospheric CO 2 [Farquhar et al, 1993;Luz et al, 1999]. These ''top-down'' techniques exploit rapid mixing by the atmosphere to smooth considerable heterogeneity at the land surface.…”

Section: Introductionmentioning

confidence: 99%

Steady state turnover time of carbon in the Australian terrestrial biosphere

Barrett¹

2002

Global Biogeochemical Cycles

119

127

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[1] The turnover time of terrestrial carbon was estimated using a multiobjective parameterization method that combined data sets of plant production, biomass, litter and soil-C observations in the calibration of a C-cycle model for the Australian continent (VAST1.1; Vegetation and Soil carbon Transfer). The method employed a genetic algorithm to minimize model-data deviations and maximize consistency between estimated model parameters and all available data. Based on the parameterization, the turnover time of biosphere C for Australia was estimated to be 78 years which is longer than global C-turnover estimates (of 26-60 years) due entirely to slower turnover of C in the upper 20 cm of soil. Turnover times of litter and deeper soil-C were similar to global values. By splitting total C in the upper 20 cm between labile and nonlabile fractions (based on published data) the turnover time of the labile pool was at least 44 years which is still longer than global estimates (9-25 years). Longer C-turnover in Australian surface soils was attributed to (1) limited soil moisture slowing decomposition more than net primary production, (2) frequent fires leading to a large fraction of nonlabile charcoal C in soil, and (3) strong adsorbing capacity for organic-C in these highly weathered soils. It was found that >89% of the C flux to the atmosphere from decomposition of organic matter originated from fine litter, coarse woody debris and the upper 20 cm of soil in all biomes.

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Decadal Δ¹⁷O record of tropospheric CO₂: Verification of a stratospheric component in the troposphere

2014

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Vegetation effects on the isotope composition of oxygen in atmospheric CO2

Cited by 393 publications

References 22 publications

Modelling assimilation and intercellular CO₂ from measured conductance: a synthesis of approaches

Modelling assimilation and intercellular CO₂ from measured conductance: a synthesis of approaches

Steady state turnover time of carbon in the Australian terrestrial biosphere

Decadal Δ¹⁷O record of tropospheric CO₂: Verification of a stratospheric component in the troposphere

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Vegetation effects on the isotope composition of oxygen in atmospheric CO2

Cited by 393 publications

References 22 publications

Modelling assimilation and intercellular CO2 from measured conductance: a synthesis of approaches

Modelling assimilation and intercellular CO2 from measured conductance: a synthesis of approaches

Steady state turnover time of carbon in the Australian terrestrial biosphere

Decadal Δ17O record of tropospheric CO2: Verification of a stratospheric component in the troposphere

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Product

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Modelling assimilation and intercellular CO₂ from measured conductance: a synthesis of approaches

Modelling assimilation and intercellular CO₂ from measured conductance: a synthesis of approaches

Decadal Δ¹⁷O record of tropospheric CO₂: Verification of a stratospheric component in the troposphere