 |
| Titel |
Relevance of mineral-organic associations in cryoturbated permafrost soils |
| VerfasserIn |
Norman Gentsch, Robert Mikutta, Jiří Bárta, Petr Čapek, Antje Gittel, Andreas Richter, Hanna Šantrůčková, Jörg Schnecker, Olga Shibistova, Tim Urich, Birgit Wild, Georg Guggenberger |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250095776
|
| Publikation (Nr.) |
 EGU/EGU2014-11248.pdf |
|
|
|
|
|
| Zusammenfassung |
| Enhanced microbial decomposition of deep buried organic matter (OM) increase the release
of CO2and CH4from high latitude ecosystems, thus being an uncertain but potentially crucial
positive feedback to global warming. The role of soil minerals as stabilization agents of OM
against microbial attack gain in importance as soon abiotic soil conditions will change in
permafrost soils. We investigated changes in storage and turnover of soil organic
carbon (OC) and total nitrogen (TN) associated with minerals in 27 cryoturbated
permafrost soils from the west to the east Siberian Arctic. Furthermore, we studied
the mineral composition and the potential of OM to interact with soil minerals
via different binding mechanisms. Mineral-associated organic matter (MOM) was
separated from particulate plant debris by density fractionation in sodium polytungstate
(density cut-off 1.6 g cm-3). Their apparent 14C ages were determined by accelerator
mass spectrometry and potential mineralization rates were analyzed in a 180 days
incubation experiments at 5 and 15°C. The mineral composition was analyzed
by X-ray diffraction and selective extractions. Desorption experiments (stepwise
extraction with KCl and NaH2PO4) using the permafrost soils as well as reference
soils from temperate regions (three Stagnolsols from Germany) were performed to
study OM sorbed to mineral surfaces or complexed with polyvalent metal ions.
The proportion of OC associated with minerals (MOC) ranged from 5.1 to 14.9
kg m-2 (average: 11.0 kg m-2), corresponding to ~55% from the total soil OC
storage (average: 20.2 ± 8.0 kg m-2) in the first meter of the Cryosols. In contrast
to temperate soils, where maximum MOC concentrations are present in topsoils,
cambic, or spodic horizons, cryoturbation in permafrost soils leads to high MOC
concentrations within the whole solum. Cryoturbated OM-rich pockets in the subsoil
store 18% (2.0 ± 1.3 kg m-2) of the MOC while another 34% (3.8 ± 3.5 kg m-2)
was located in the uppermost permafrost. In topsoil horizons, mineralization rates
showed a similar pattern for MOM and the bulk soil controls. In contrast, even
higher MOM respiration rates then the bulk control were found in the cryoturbated
OM-rich pockets and permafrost horizons. These findings deviate from temperate soil
environments where MOM is considered to contribute to a ’stabilized pool’ with
mean residence times from hundreds to thousands of years. Statistical analysis
indicated that mineral-organic interactions primarily occurred with poorly crystalline
Fe and Al phases and Fe/Al-OM complexes. However, the minor desorption of
organic polyelectrolytes by NaH2PO4 in permafrost soils indicated that significantly
lower amounts of OC were bound by ligand exchange to Fe and Al minerals or the
edges of clay minerals in permafrost soils compared to the temperate reference
soils. Therefore, stabilization of OM by mineral surfaces or polyvalent metal ions
appears to be of minor relevance in arctic environments compared to temperate soils. |
|
|
|
|
|
|