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| Titel |
Seasonal variations in soil carbonic anhydrase activity in a pine forest ecosystem as inferred from soil CO18O flux measurements |
| VerfasserIn |
Jerome Ogee, Lisa Wingate, Alexandre Bosc, Regis Burlett |
| 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 |
250105776
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| Publikation (Nr.) |
 EGU/EGU2015-5342.pdf |
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| Zusammenfassung |
| Quantifying terrestrial carbon storage and predicting the sensitivity of ecosystems to climate
change relies on our ability to obtain observational constraints on photosynthesis and
respiration at large scales (ecosystem, regional and global). Photosynthesis (GPP), the largest
CO2 flux from the land surface, is currently estimated with considerable uncertainty (1-3).
Robust estimates of global GPP can be obtained from an atmospheric budget of
the oxygen isotopic composition (δ18O) of atmospheric CO2, provided that we
have a good knowledge of the δ18O signatures of the terrestrial CO2 fluxes (1,4).
The latter reflect the δ18O of leaf and soil water pools because CO2 exchanges
“isotopically” with water [CO2+H218O/H2O+CO18O]. This exchange can be
accelerated by the enzyme carbonic anhydrase (CA). In leaves, where CA is present
and abundant, this isotopic equilibrium is reached almost instantaneously. As a
consequence, and because soil and leaf water pools have different δ18O signatures,
CO2 fluxes from leaves and soils carry very distinct δ18O signals and can thus be
tracked from the fluctuations in the δ18O of atmospheric CO2 (δa). There is growing
evidence that the accelerated isotopic exchange between CO2 and water due to
CA activity is a widespread phenomenon in soils as well (4). At the global scale,
accounting for soil CA activity dramatically shifts the influence of soil and leaf
fluxes on δa, thus changing the estimates of terrestrial gross CO2 fluxes (1,4). In this
talk we will briefly present the current state of understanding of the environmental
and ecological causes behind the variability in CA activity observed in soils and
illustrate, using field data from a temperate pine forest, how soil CA activity varies
over a single growing season and how it responds to soil surface environmental
variables.
References
1. L. R. Welp et al., Interannual variability in the oxygen isotopes of atmospheric CO2 driven
by El Niño, Nature 477, 579–582 (2011).
2. C. Beer et al., Terrestrial Gross Carbon Dioxide Uptake: Global Distribution and
Covariation with Climate, Science 329, 834–838 (2010).
3. C. Frankenberg et al., New global observations of the terrestrial carbon cycle from
GOSAT: Patterns of plant fluorescence with gross primary productivity, Geophys. Res. Lett.
38 (2011), doi:10.1029/2011GL048738.
4. L. Wingate et al., The impact of soil microorganisms on the global budget of δ18O in
atmospheric CO2, Proceedings of the National Academy of Sciences 106, 22411–22415
(2009). |
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