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Evaluation of 11 terrestrial carbon-nitrogen cycle models against observations from two temperate Free-Air CO2 Enrichment studies.

Zaehle S, Medlyn BE, De Kauwe MG, Walker AP, Dietze MC, Hickler T, Luo Y, Wang YP, El-Masri B, Thornton P, Jain A, Wang S, Warlind D, Weng E, Parton W, Iversen CM, Gallet-Budynek A, McCarthy H, Finzi A, Hanson PJ, Prentice IC, Oren R, Norby RJ - New Phytol. (2014)

Bottom Line: Nonetheless, many models showed qualitative agreement with observed component processes.The results suggest that improved representation of above-ground-below-ground interactions and better constraints on plant stoichiometry are important for a predictive understanding of eCO2 effects.Improved accuracy of soil organic matter inventories is pivotal to reduce uncertainty in the observed C-N budgets.

View Article: PubMed Central - PubMed

Affiliation: Biogeochemical Integration Department, Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, D-07745, Jena, Germany.

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Total change in ecosystem carbon (ΔCorg) as a result of elevated atmospheric [CO2] (eCO2) at the Duke (a) and Oak Ridge National Laboratory (ORNL) (b) Free-Air CO2 Enrichment (FACE) sites resulting from changes in the total organic ecosystem nitrogen (N) store (ΔNorg), and vegetation and soil C : N ratios (ΔC : Nveg and ΔC : Nsoil), as well as changes in the fractionation of total ecosystem N between vegetation and soil, measured as the fraction of total ecosystem N in vegetation (fveg = Nveg/Norg). The error bars denote ± 1SE.
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fig09: Total change in ecosystem carbon (ΔCorg) as a result of elevated atmospheric [CO2] (eCO2) at the Duke (a) and Oak Ridge National Laboratory (ORNL) (b) Free-Air CO2 Enrichment (FACE) sites resulting from changes in the total organic ecosystem nitrogen (N) store (ΔNorg), and vegetation and soil C : N ratios (ΔC : Nveg and ΔC : Nsoil), as well as changes in the fractionation of total ecosystem N between vegetation and soil, measured as the fraction of total ecosystem N in vegetation (fveg = Nveg/Norg). The error bars denote ± 1SE.

Mentions: The large observed increase in vegetation biomass at Duke Forest was supported mostly by a redistribution of N from soil to vegetation, as soil N stocks in the upper soil layers have probably declined over the course of the experiment (Fig.9a). However, there were significant differences in the magnitude of the transfer and vegetation C : N changes among the plots, causing large uncertainty in the attribution of the observed vegetation C increase. Although fNup also increased in ORNL FACE, there was not a sustained increase in biomass N and C, because the rapid turnover of leaves and roots did not lead to a sustained increase in biomass N and C, which instead caused C and N sequestration in SOM (within the detection limit; Fig.9b). At both sites, bulk vegetation C : N decreased slightly with eCO2, despite the larger C : N in foliage, because of the larger contribution of foliage and root biomass to total biomass.


Evaluation of 11 terrestrial carbon-nitrogen cycle models against observations from two temperate Free-Air CO2 Enrichment studies.

Zaehle S, Medlyn BE, De Kauwe MG, Walker AP, Dietze MC, Hickler T, Luo Y, Wang YP, El-Masri B, Thornton P, Jain A, Wang S, Warlind D, Weng E, Parton W, Iversen CM, Gallet-Budynek A, McCarthy H, Finzi A, Hanson PJ, Prentice IC, Oren R, Norby RJ - New Phytol. (2014)

Total change in ecosystem carbon (ΔCorg) as a result of elevated atmospheric [CO2] (eCO2) at the Duke (a) and Oak Ridge National Laboratory (ORNL) (b) Free-Air CO2 Enrichment (FACE) sites resulting from changes in the total organic ecosystem nitrogen (N) store (ΔNorg), and vegetation and soil C : N ratios (ΔC : Nveg and ΔC : Nsoil), as well as changes in the fractionation of total ecosystem N between vegetation and soil, measured as the fraction of total ecosystem N in vegetation (fveg = Nveg/Norg). The error bars denote ± 1SE.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4288990&req=5

fig09: Total change in ecosystem carbon (ΔCorg) as a result of elevated atmospheric [CO2] (eCO2) at the Duke (a) and Oak Ridge National Laboratory (ORNL) (b) Free-Air CO2 Enrichment (FACE) sites resulting from changes in the total organic ecosystem nitrogen (N) store (ΔNorg), and vegetation and soil C : N ratios (ΔC : Nveg and ΔC : Nsoil), as well as changes in the fractionation of total ecosystem N between vegetation and soil, measured as the fraction of total ecosystem N in vegetation (fveg = Nveg/Norg). The error bars denote ± 1SE.
Mentions: The large observed increase in vegetation biomass at Duke Forest was supported mostly by a redistribution of N from soil to vegetation, as soil N stocks in the upper soil layers have probably declined over the course of the experiment (Fig.9a). However, there were significant differences in the magnitude of the transfer and vegetation C : N changes among the plots, causing large uncertainty in the attribution of the observed vegetation C increase. Although fNup also increased in ORNL FACE, there was not a sustained increase in biomass N and C, because the rapid turnover of leaves and roots did not lead to a sustained increase in biomass N and C, which instead caused C and N sequestration in SOM (within the detection limit; Fig.9b). At both sites, bulk vegetation C : N decreased slightly with eCO2, despite the larger C : N in foliage, because of the larger contribution of foliage and root biomass to total biomass.

Bottom Line: Nonetheless, many models showed qualitative agreement with observed component processes.The results suggest that improved representation of above-ground-below-ground interactions and better constraints on plant stoichiometry are important for a predictive understanding of eCO2 effects.Improved accuracy of soil organic matter inventories is pivotal to reduce uncertainty in the observed C-N budgets.

View Article: PubMed Central - PubMed

Affiliation: Biogeochemical Integration Department, Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, D-07745, Jena, Germany.

Show MeSH
Related in: MedlinePlus