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| Titel |
A new chamber method for the simultaneous determination of δ¹³C and δ¹⁸O in soil derived CO2 |
| VerfasserIn |
Nils Prolingheuer, Harry Vereecken, Jens-Arne Subke |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250047649
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| Zusammenfassung |
| Stable carbon (C) isotopes have been instrumental in constraining current estimates of the
terrestrial C balance. Recently, Wingate et al. (2010; Global Change Biology, 16, 3048-3064)
have shown a strong disequilibrium in δ18O between leaf and soil derived CO2, raising hopes
that different respiratory sources (e.g. plant vs. soil) can be distinguished using the
atmospheric abundance of CO18O at larger spatial scales. However, uncertainty remains
about the role of carbonic anhydrase (CA), an enzyme that efficiently catalyzes the exchange
of O during CO2 hydration in soils. The activity of CA determines the degree to
which soil derived CO2 carries the isotopic signature of soil surface water (e.g.
in the litter layer). Experimental work is needed to clarify this exchange of 18O
in the soil, and the potential to identify root and rhizosphere-derived CO2 using
18O.
In order to constrain ecosystem C exchange estimates on the basis of 18O abundance in
atmospheric CO2, we now require new measuring systems that allow simultaneous capture of
δ18O and δ13C signatures of soil derived CO2. To date, many laser absorption methodologies
require considerable electric power and frequent calibration. However, a new generation of
analysers based on a cavity enhanced laser absorption spectroscopy technique has recently
become available and has considerable potential to deliver fast isotopic measurements with
dramatically reduced power consumption and calibration requirements. We present first
results from a new analytical set-up based on such a fast isotope analyser (model CCIA-36d,
Los Gatos Research) coupled to a dynamic soil chamber. We use the changes in isotopic
abundance (of both 13C and 18O) as CO2 concentrations build up during chamber
closure to determine soil 13CO2 and CO18O fluxes. Using a series of replicated soil
microcosms, we assess the role of (1) rooted vs. un-rooted soil, (2) simulated rain
events, and (3) soil warming on the δ18O and δ13C signatures of soil derived CO2. |
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