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| Titel |
The influence of soil carbonic anhydrase on the partitioning of gross CO2 fluxes using the oxygen isotopes of CO2 and water. |
| VerfasserIn |
L. Wingate, J. Ogée, M. Cuntz, U. Seibt, P. Peylin, B. Genty, I. Reiter, J. Grace |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250021015
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| Zusammenfassung |
| Measuring terrestrial gross CO2 fluxes at large scales presents one of the main challenges in
global carbon cycle research. The oxygen isotopic composition (δ18O) of atmospheric CO2
offers the possibility to partition net CO2 fluxes into photosynthesis and respiration at
ecosystem, regional and global scales. This approach relies on a detailed knowledge of the
δ18O signature of the terrestrial gross CO2 fluxes. The latter reflects the δ18O of leaf and soil
water because CO2 exchanges isotopically with water. This exchange can be accelerated by
the enzyme carbonic anhydrase (CA). The high CA content in leaves of plants amplifies the
impact of leaf photosynthesis on the δ18O of atmospheric CO2 (δa) by enhancing the
equilibration of atmospheric CO2 with isotopically enriched leaf water. Here, we report that
the accelerated isotopic exchange between CO2 and water due to CA activity may be a
widespread phenomenon in soils as well. Across a range of ecosystems, we found that
CO2 hydration was 10 to 300 times faster than the uncatalysed rate, with highest
values in the hottest ecosystems. 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. At a time when new laser technologies are poised
to deliver more extensive data coverage of variations in δa, our finding indicates
that δa signals should enable us to constrain CO2 gross fluxes in regions where
this information has been particularly difficult to obtain, such as in the tropics. |
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