Evaluation of 11 terrestrial carbon-nitrogen cycle models against observations from two temperate Free-Air CO2 Enrichment studies.
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.
Affiliation: Biogeochemical Integration Department, Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, D-07745, Jena, Germany.Show MeSH
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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.
Affiliation: Biogeochemical Integration Department, Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, D-07745, Jena, Germany.