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Titel |
Isotopic composition of soil CO2 to evaluate microbial availability of organic carbon |
VerfasserIn |
J. Pausch, Y. Kuzyakov |
Konferenz |
EGU General Assembly 2012
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 14 (2012) |
Datensatznummer |
250069028
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Zusammenfassung |
The production of CO2 in soil strongly depends on microbial availability of organic carbon
(C). It is obvious, that C that entered the soil recently is more easily available for
microorganisms in comparison to older C: However, only very few approaches allow for a
quantitative estimation of microbial availability of C in relation to the time it is entering the
soil. We hypothesized that δ13C values of CO2 and of soil organic matter (SOM) after a C3 to
C4 vegetation change will enable us to calculate the relative availability of younger and
older C sources for microorganisms. Soil CO2 was sampled over one vegetation
period at depths of 10, 40-50 and 60-70 cm at three treatments: a C3 reference
(wheat), a C4/fallow (fallow after one year of maize cropping), and a C4/C4 (two
years of maize cropping). Based on the δ13C of CO2 purified from the admixture of
atmospheric CO2 by the Miller/Tans model and on the δ13C values of SOM, the
contributions of younger (C4) and older (C3) C sources to CO2 and SOM were
assessed. Depending on soil depth and the presence of living roots, the contribution
of C4-C to soil CO2 ranged from 20 to 60 %, but that of C4-C to SOM was less
than 5 %. By comparing the contributions of C3-C and C4-C to CO2 and SOM,
we found that the relative availability of organics recently introduced into the soil
was about 10 times higher than the availability of C stabilized in soil for longer
than one year. We concluded that simultaneous analysis of the δ13C values of both
SOM and of CO2 allows not only for the quantification of the CO2 sources, but
also for the estimation of the microbial availability of soil C pools of different age. |
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