 |
| Titel |
Storage and turnover of organic matter fractions along a Siberian Arctic soil transect |
| VerfasserIn |
Norman Gentsch, Robert Mikutta, Olga Shibistova, Georg Guggenberger |
| Konferenz |
EGU General Assembly 2013
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250082387
|
|
|
|
|
|
| Zusammenfassung |
| Recent observation and climate models demonstrate that arctic ecosystems are already
affected by climate warming, as revealed by continuous permafrost degradation
and increase of active layer depths. Variations of organic matter (OM) storage in
different soil horizons and the OM quality are likely the major drivers of trace gas
emissions to the atmosphere. A better understanding of the biogeochemical cycling
of OM in permafrost environments is the key to predict future climate changes
and the role of terrestrial arctic regions. This study investigates the storage and
turnover patterns of OM in functionally different pools, i.e., in particulate plant debris,
extractable-water-soluble OM, and mineral-associated OM in permafrost soils along a
West-East Siberian transect in the Russian Arctic. We quantified the stocks of total soil
organic C (OC) and the respective OM fractions for the first soil meter. Furthermore, we
estimated their apparent 14C ages by accelerator mass spectrometry, and determined the
mineralization rates and bioavailability of particulate, mineral-bound, and bulk
OM in a 90-day incubation experiment. Particulate OM was separated from the
mineral-associated OM fraction by density fractionation with sodium polytungstate
(density cut-off 1.6 g cm-3) and the OM liberated by this treatment was quantified.
Considerable differences in OM storage existed from the West- to the East Siberian Arctic.
Cryosols of the Central- and East Siberian sampling sites stored on average 56%
more OC than those in West Siberia (25 ± 7 kg m-2versus 11 ± 4 kg m-2 to 1 m
soil depth). However, the proportion of the three OM fractions to total OM was
similar among the sites. In mineral soil horizons, on average, 17 ± 5% of the total
OM was particulate OM, 61 ± 10% was associated with minerals, and 21 ± 3%
could be mobilized in dissolved forms during density fractionation. Except for West
Siberian soils, ~30% of the OM of the first soil meter was stored in permafrost while
another 13-30% was located in cryoturbated horizons. In contrast to temperate soils,
where particulate OM turns over much faster than the mineral-associated OM, the
differences in apparent 14C ages of the fractions in comparable soil horizons from our
study sites were minor. Moreover, the incubation experiment showed only slight
differences in total mineralization rates among the fractions and the bulk soil. In
the cryoturbated horizons the total respiration rates of the mineral-associated OM
fraction exceeded even those of particulate OM. Therefore, we hypothesize that in
arctic environments, stabilization of OM by mineral surfaces or metal ions is of
minor relevance compared to temperate soils. External constraints such as high
moisture, low soil temperature, and the annual or perennial frozen stage are probably
more important in controlling the persistence of OM in permafrost-affected soils. |
|
|
|
|
|
|