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| Titel |
Optimal plant nitrogen use improves model representation of vegetation response to elevated CO2 |
| VerfasserIn |
Silvia Caldararu, Melanie Kern, Jan Engel, Sönke Zaehle |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250144276
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| Publikation (Nr.) |
 EGU/EGU2017-8084.pdf |
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| Zusammenfassung |
| Existing global vegetation models often cannot accurately represent observed ecosystem
behaviour under transient conditions such as elevated atmospheric CO2, a problem that can
be attributed to an inflexibility in model representation of plant responses. Plant optimality
concepts have been proposed as a solution to this problem as they offer a way to represent
plastic plant responses in complex models. Here we present a novel, next generation
vegetation model which includes optimal nitrogen allocation to and within the canopy as well
as optimal biomass allocation between above- and belowground components in response to
nutrient and water availability. The underlying hypothesis is that plants adjust their use
of nitrogen in response to environmental conditions and nutrient availability in
order to maximise biomass growth. We show that for two FACE (Free Air CO2
enrichment) experiments, the Duke forest and Oak Ridge forest sites, the model
can better predict vegetation responses over the duration of the experiment when
optimal processes are included. Specifically, under elevated CO2 conditions, the
model predicts a lower optimal leaf N concentration as well as increased biomass
allocation to fine roots, which, combined with a redistribution of leaf N between the
Rubisco and chlorophyll components, leads to a continued NPP response under high
CO2, where models with a fixed canopy stoichiometry predict a quick onset of
N limitation.Existing global vegetation models often cannot accurately represent
observed ecosystem behaviour under transient conditions such as elevated atmospheric
CO2, a problem that can be attributed to an inflexibility in model representation
of plant responses. Plant optimality concepts have been proposed as a solution to
this problem as they offer a way to represent plastic plant responses in complex
models. Here we present a novel, next generation vegetation model which includes
optimal nitrogen allocation to and within the canopy as well as optimal biomass
allocation between above- and belowground components in response to nutrient
and water availability. The underlying hypothesis is that plants adjust their use of
nitrogen in response to environmental conditions and nutrient availability in order to
maximise biomass growth. We show that for two FACE (Free Air CO2 enrichment)
experiments, the Duke forest and Oak Ridge forest sites, the model can better predict
vegetation responses over the duration of the experiment when optimal processes
are included. Specifically, under elevated CO2 conditions, the model predicts a
lower optimal leaf N concentration as well as increased biomass allocation to fine
roots, which, combined with a redistribution of leaf N between the Rubisco and
chlorophyll components, leads to a continued NPP response under high CO2, where
models with a fixed canopy stoichiometry predict a quick onset of N limitation. |
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