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| Titel |
Low vertical transfer rates of carbon inferred from radiocarbon analysis in an Amazon Podzol |
| VerfasserIn |
C. A. Sierra, E. M. Jimenez, B. Reu, M. C. Peñuela, A. Thuille, C. A. Quesada |
| 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 ; 10, no. 6 ; Nr. 10, no. 6 (2013-06-01), S.3455-3464 |
| Datensatznummer |
250018262
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| Publikation (Nr.) |
 copernicus.org/bg-10-3455-2013.pdf |
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| Zusammenfassung |
| Hydromorphic Podzol soils in the Amazon Basin generally support low-stature
forests with some of the lowest amounts of aboveground net primary production
(NPP) in the region. However, they can also exhibit large values of
belowground NPP that can contribute significantly to the total annual inputs
of organic matter into the soil. These hydromorphic Podzol soils also exhibit
a horizon rich in organic matter at around 1–2 m depth, presumably as a
result of eluviation of dissolved organic matter and sesquioxides of Fe and
Al. Therefore, it is likely that these ecosystems store large quantities of
carbon by (1) large amounts of C inputs to soils dominated by their high
levels of fine-root production, (2) stabilization of organic matter in an
illuviation horizon due to significant vertical transfers of C. To assess
these ideas we studied soil carbon dynamics using radiocarbon in two adjacent
Amazon forests growing on contrasting soils: a hydromorphic Podzol and a
well-drained Alisol supporting a high-stature terra firme forest.
Our measurements showed similar concentrations of C and radiocarbon in the
litter layer and the first 5 cm of the mineral soil for both sites.
This result is consistent with the idea that the hydromorphic Podzol soil has
similar soil C storage and cycling rates compared to the well-drained Alisol
that supports a more opulent vegetation. However, we found important
differences in carbon dynamics and transfers along the vertical profile. At
both soils, we found similar radiocarbon concentrations in the subsoil, but
the carbon released after incubating soil samples presented radiocarbon
concentrations of recent origin in the Alisol, but not in the Podzol. There
were no indications of incorporation of C fixed after 1950 in the illuvial
horizon of the Podzol. With the aid of a simulation model, we predicted that
only a minor fraction (1.7%) of the labile carbon decomposed in the
topsoil is transferred to the subsoil of the Podzol, while this proportional
transfer is about 30% in the Alisol. Furthermore, our estimates were 8
times lower than previous estimations of vertical C transfers in Amazon
Podzols, and question the validity of these previous estimations for all
Podzols within the Amazon Basin. Our results also challenge our previous
ideas about the genesis of these particular soils and suggest that either
they are not true Podzols or the podzolization processes had already stopped. |
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