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| Titel |
A model using marginal efficiency of investment to analyze carbon and nitrogen interactions in terrestrial ecosystems (ACONITE Version 1) |
| VerfasserIn |
R. Q. Thomas, M. Williams |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 7, no. 5 ; Nr. 7, no. 5 (2014-09-12), S.2015-2037 |
| Datensatznummer |
250115719
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| Publikation (Nr.) |
 copernicus.org/gmd-7-2015-2014.pdf |
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| Zusammenfassung |
| Carbon (C) and nitrogen (N) cycles are coupled in terrestrial ecosystems
through multiple processes including photosynthesis, tissue allocation,
respiration, N fixation, N uptake, and decomposition of litter and soil
organic matter. Capturing the constraint of N on terrestrial C uptake and
storage has been a focus of the Earth System Modeling community. However,
there is little understanding of the trade-offs and sensitivities of
allocating C and N to different tissues in order to optimize the
productivity of plants. Here we describe a new, simple model of ecosystem
C–N cycling and interactions (ACONITE), that builds on theory related to
plant economics in order to predict key ecosystem properties (leaf area
index, leaf C : N, N fixation, and plant C use efficiency) based on the
outcome of assessments of the marginal change in net C or N uptake
associated with a change in allocation of C or N to plant tissues. We
simulated and evaluated steady-state ecosystem stocks and fluxes in three
different forest ecosystems types (tropical evergreen, temperate deciduous,
and temperate evergreen). Leaf C : N differed among the three ecosystem types
(temperate deciduous < tropical evergreen < temperature
evergreen), a result that compared well to observations from a global
database describing plant traits. Gross primary productivity (GPP) and net
primary productivity (NPP) estimates compared well to observed fluxes at the
simulation sites. Simulated N fixation at steady-state, calculated based on
relative demand for N and the marginal return on C investment to acquire N,
was an order of magnitude higher in the tropical forest than in the
temperate forest, consistent with observations. A sensitivity analysis
revealed that parameterization of the relationship between leaf N and leaf
respiration had the largest influence on leaf area index and leaf C : N. A parameter governing how photosynthesis scales
with day length had the largest influence on total vegetation C, GPP, and
NPP. Multiple parameters associated with photosynthesis, respiration, and N
uptake influenced the rate of N fixation. Overall, our ability to constrain
leaf area index and allow spatially and temporally variable leaf C : N can
help address challenges simulating these properties in ecosystem and Earth
System models. Furthermore, the simple approach with emergent properties
based on coupled C–N dynamics has potential for use in research that uses
data-assimilation methods to integrate data on both the C and N cycles to
improve C flux forecasts. |
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