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| Titel |
Terrestrial cycling of 13CO2 by photosynthesis, respiration, and biomass burning in SiBCASA |
| VerfasserIn |
I. R. van der Velde, J. B. Miller, K. Schaefer, G. R. van der Werf, M. C. Krol, W. Peters |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 23 ; Nr. 11, no. 23 (2014-12-01), S.6553-6571 |
| Datensatznummer |
250117702
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| Publikation (Nr.) |
 copernicus.org/bg-11-6553-2014.pdf |
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| Zusammenfassung |
We present an enhanced version of the SiBCASA terrestrial biosphere model
that is extended with (a) biomass burning emissions from the SiBCASA carbon
pools using remotely sensed burned area from the Global Fire Emissions
Database (GFED), (b) an isotopic discrimination scheme that calculates
13C signatures of photosynthesis and autotrophic respiration, and (c) a
separate set of 13C pools to carry isotope ratios into heterotrophic
respiration. We quantify in this study the terrestrial exchange of CO2
and 13CO2 as a function of environmental changes in humidity and
biomass burning.
The implementation of biomass burning yields similar fluxes as CASA-GFED both
in magnitude and spatial patterns. The implementation of isotope exchange
gives a global mean discrimination value of 15.2‰, ranges
between 4 and 20‰ depending on the photosynthetic pathway in the
plant, and compares favorably (annually and seasonally) with other published
values. Similarly, the isotopic disequilibrium is similar to other studies
that include a small effect of biomass burning as it shortens the turnover of
carbon. In comparison to measurements, a newly modified starch/sugar storage
pool propagates the isotopic discrimination anomalies to respiration much
better. In addition, the amplitude of the drought response by SiBCASA is
lower than suggested by the measured isotope ratios. We show that a slight
increase in the stomatal closure for large vapor pressure deficit would
amplify the respired isotope ratio variability. Our study highlights the
importance of isotope ratio observations of 13C to assess and improve
biochemical models like SiBCASA, especially with regard to the allocation and
turnover of carbon and the responses to drought. |
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