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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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Cumulative plant nitrogen (N) uptake as a result of elevated atmospheric [CO2] (eCO2) over the length of the experiment, and its assignment to different mechanisms according to Eqns 4 and 5 at the Duke (a) and Oak Ridge National Laboratory (ORNL) (b) Free-Air CO2 Enrichment (FACE) sites. Positive values indicate an increase in plant N uptake, and negative values a decline. (c–e) Exemplary time courses of the net N balance for Duke forest, as predicted by CABLE (c), CLM4 (d) and OCN (e). ΔfNup, plant nitrogen uptake; , change in net N mineralization caused by a change in the soil organic N turnover time relative to the soil organic C turnover time; ΔNSOM, change in net N mineralization caused by a change in the organic N pool; ΔNNE, change in the ecosystem N balance (sum of N increases from biological N fixation and atmospheric N deposition and N losses to leaching and gaseous emissions); ΔNinorg, changes in the inorganic N pool. The error bars on the observations denote ± 1SE.
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fig08: Cumulative plant nitrogen (N) uptake as a result of elevated atmospheric [CO2] (eCO2) over the length of the experiment, and its assignment to different mechanisms according to Eqns 4 and 5 at the Duke (a) and Oak Ridge National Laboratory (ORNL) (b) Free-Air CO2 Enrichment (FACE) sites. Positive values indicate an increase in plant N uptake, and negative values a decline. (c–e) Exemplary time courses of the net N balance for Duke forest, as predicted by CABLE (c), CLM4 (d) and OCN (e). ΔfNup, plant nitrogen uptake; , change in net N mineralization caused by a change in the soil organic N turnover time relative to the soil organic C turnover time; ΔNSOM, change in net N mineralization caused by a change in the organic N pool; ΔNNE, change in the ecosystem N balance (sum of N increases from biological N fixation and atmospheric N deposition and N losses to leaching and gaseous emissions); ΔNinorg, changes in the inorganic N pool. The error bars on the observations denote ± 1SE.

Mentions: In SDGVM, fNup was driven with observations and therefore this model is not considered further in this section. Among the other models, there are two alternative implementations of the processes that allow for a preferential increase in fNup compared with microbial N immobilization under eCO2, leading to contrasting predictions (Fig.8a,b).


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)

Cumulative plant nitrogen (N) uptake as a result of elevated atmospheric [CO2] (eCO2) over the length of the experiment, and its assignment to different mechanisms according to Eqns 4 and 5 at the Duke (a) and Oak Ridge National Laboratory (ORNL) (b) Free-Air CO2 Enrichment (FACE) sites. Positive values indicate an increase in plant N uptake, and negative values a decline. (c–e) Exemplary time courses of the net N balance for Duke forest, as predicted by CABLE (c), CLM4 (d) and OCN (e). ΔfNup, plant nitrogen uptake; , change in net N mineralization caused by a change in the soil organic N turnover time relative to the soil organic C turnover time; ΔNSOM, change in net N mineralization caused by a change in the organic N pool; ΔNNE, change in the ecosystem N balance (sum of N increases from biological N fixation and atmospheric N deposition and N losses to leaching and gaseous emissions); ΔNinorg, changes in the inorganic N pool. The error bars on the observations denote ± 1SE.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig08: Cumulative plant nitrogen (N) uptake as a result of elevated atmospheric [CO2] (eCO2) over the length of the experiment, and its assignment to different mechanisms according to Eqns 4 and 5 at the Duke (a) and Oak Ridge National Laboratory (ORNL) (b) Free-Air CO2 Enrichment (FACE) sites. Positive values indicate an increase in plant N uptake, and negative values a decline. (c–e) Exemplary time courses of the net N balance for Duke forest, as predicted by CABLE (c), CLM4 (d) and OCN (e). ΔfNup, plant nitrogen uptake; , change in net N mineralization caused by a change in the soil organic N turnover time relative to the soil organic C turnover time; ΔNSOM, change in net N mineralization caused by a change in the organic N pool; ΔNNE, change in the ecosystem N balance (sum of N increases from biological N fixation and atmospheric N deposition and N losses to leaching and gaseous emissions); ΔNinorg, changes in the inorganic N pool. The error bars on the observations denote ± 1SE.
Mentions: In SDGVM, fNup was driven with observations and therefore this model is not considered further in this section. Among the other models, there are two alternative implementations of the processes that allow for a preferential increase in fNup compared with microbial N immobilization under eCO2, leading to contrasting predictions (Fig.8a,b).

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