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| Titel |
Modelling microbial exchanges between forms of soil nitrogen in contrasting ecosystems |
| VerfasserIn |
M. Pansu, D. Machado, P. Bottner, L. Sarmiento |
| 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. 4 ; Nr. 11, no. 4 (2014-02-20), S.915-927 |
| Datensatznummer |
250117232
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| Publikation (Nr.) |
 copernicus.org/bg-11-915-2014.pdf |
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| Zusammenfassung |
| Although nitrogen (N) is often combined with carbon (C) in organic
molecules, C passes from the air to the soil through plant photosynthesis,
whereas N passes from the soil to plants through a chain of microbial
conversions. However, dynamic models do not fully consider the
microorganisms at the centre of exchange processes between organic and
mineral forms of N. This study monitored the transfer of 14C and
15N between plant materials, microorganisms, humified compartments, and
inorganic forms in six very different ecosystems along an altitudinal
transect. The microbial conversions of the 15N forms appear to be
strongly linked to the previously modelled C cycle, and the same equations
and parameters can be used to model both C and N cycles. The only
difference is in the modelling of the flows between microbial and inorganic
forms. The processes of mineralization and immobilization of N appear to be
regulated by a two-way microbial exchange depending on the C : N ratios of
microorganisms and available substrates. The MOMOS (Modelling of Organic Matter of Soils) model has already been
validated for the C cycle and also appears to be valid for the prediction of
microbial transformations of N forms. This study shows that the hypothesis
of microbial homeostasis can give robust predictions at global scale.
However, the microbial populations did not appear to always be independent
of the external constraints. At some altitudes their C : N ratio could be
better modelled as decreasing during incubation and increasing with
increasing C storage in cold conditions. The ratio of potentially
mineralizable-15N/inorganic-15N and the 15N stock in the
plant debris and the microorganisms was modelled as increasing with altitude,
whereas the 15N storage in stable humus was modelled as decreasing with
altitude. This predicts that there is a risk that mineralization of organic
reserves in cold areas may increase global warming. |
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