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| Titel |
Modeling forest C and N allocation responses to free-air CO2 enrichment |
| VerfasserIn |
Kristina Luus, Martin De Kauwe, Anthony Walker, Christian Werner, Colleen Iversen, Heather McCarthy, Belinda Medlyn, Richard Norby, Ram Oren, Donald Zak, Sönke Zaehle |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250106283
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| Publikation (Nr.) |
 EGU/EGU2015-5946.pdf |
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| Zusammenfassung |
| Vegetation allocation patterns and soil-vegetation partitioning of C and N are predicted to
change in response to rising atmospheric concentrations of CO2. These allocation responses
to rising CO2 have been examined at the ecosystem level through through free-air CO2
enrichment (FACE) experiments, and their global implications for the timing of progressive N
limitation (PNL) and C sequestration have been predicted for ~100 years using a
variety of ecosystem models. However, recent FACE model-data syntheses studies
[1,2,3] have indicated that ecosystem models do not capture the 5-10 year site-level
ecosystem allocation responses to elevated CO2. This may be due in part to the
missing representation of the rhizosphere interactions between plants and soil biota in
models.
Ecosystem allocation of C and N is altered by interactions between soil and vegetation
through the priming effect: as plant N availability diminishes, plants respond physiologically
by altering their tissue allocation strategies so as to increase rates of root growth and
rhizodeposition. In response, either soil organic material begins to accumulate, which hastens
the onset of PNL, or soil microbes start to decompose C more rapidly, resulting in increased
N availability for plant uptake, which delays PNL.
In this study, a straightforward approach for representing rhizosphere interactions
in ecosystem models was developed through which C and N allocation to roots
and rhizodeposition responds dynamically to elevated CO2 conditions,Âmodifying
soil decomposition ratesÂwithout pre-specification of the direction in which soil
C and N accumulation should shift in response to elevated CO2. This approach
was implemented in a variety of ecosystem models ranging from stand (G’DAY),
to land surface (CLM 4.5, O-CN), to dynamic global vegetation (LPJ-GUESS)
models.
Comparisons against data from three forest FACE sites (Duke, Oak Ridge & Rhinelander)
indicated that representing rhizosphere interactions allowed models to more reliably capture
responses of ecosystem C and N allocation to free-air CO2 enrichment because they were
able to simulate the priming effect. Insights were therefore gained into between-site
differences observed in forest FACE experiments, and the underlying physiological and
biogeochemical mechanisms determining ecosystem C and N allocation responses to elevated
CO2.
References
1. De Kauwe, M. G., et al. (2014), Where does the carbon go? A model–data
intercomparison of vegetation carbon allocation and turnover processes at two temperate
forest free-air CO2 enrichment sites, New Phytologist, 203, 883–899.
2. Walker, A. P., et al. (2014), Comprehensive ecosystem model-data synthesis using
multiple data sets at two temperate forest free-air CO2 enrichment experiments: Model
performance at ambient CO2 concentration, Journal of Geophysical Research:
Biogeosciences, 119, 937–964.
3. Zaehle, S., et al. (2014), Evaluation of 11 terrestrial carbon–nitrogen cycle models
against observations from two temperate Free-Air CO2 Enrichment studies, New
Phytologist, 202 (3), 803–822. |
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