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| Titel |
Carbon isotopic composition of branched tetraether membrane lipids in soils suggest a rapid turnover and a heterotrophic life style of their source organism(s) |
| VerfasserIn |
J. W. H. Weijers, Guido L. B. Wiesenberg, R. Bol, E. C. Hopmans, R. D. Pancost |
| 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 ; 7, no. 9 ; Nr. 7, no. 9 (2010-09-28), S.2959-2973 |
| Datensatznummer |
250004978
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| Publikation (Nr.) |
 copernicus.org/bg-7-2959-2010.pdf |
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| Zusammenfassung |
| Branched Glycerol Dialkyl Glycerol Tetraethers (GDGTs) are membrane spanning
lipids synthesised by as yet unknown bacteria that thrive in soils and peat.
In order to obtain more information on their ecological niche, the stable
carbon isotopic composition of branched GDGT-derived alkanes, obtained upon
ether bond cleavage, has been determined in a peat and various soils, i.e. forest, grassland and cropland, covered by various vegetation types, i.e.,
C3- vs. C4-plant type. These δ13C values are compared
with those of bulk organic matter and higher plant derived n-alkanes from the
same soils. With average δ13C values of −28‰, branched GDGTs in
C3 soils are only slightly depleted (ca. 1‰) relative to bulk organic
carbon and on average 8.5‰ enriched relative to plant wax-derived long-chain
n-alkanes ( nC29–nC33). In an Australian soil dominantly covered with
C4 type vegetation, the branched GDGTs have a δ13C value
of −18‰, clearly higher than observed in soils with C3 type vegetation.
As with C3 vegetated soils, branched GDGT δ13C values are
slightly depleted (1‰) relative to bulk organic carbon and enriched (ca. 5‰)
relative to n-alkanes in this soil. The δ13C values of branched
GDGT lipids being similar to bulk organic carbon and their co-variation with
those of bulk organic carbon and plant waxes, suggest a heterotrophic life
style and assimilation of relatively heavy and likely labile substrates for
the as yet unknown soil bacteria that synthesise the branched GDGT lipids.
However, a chemoautotrophic lifestyle, i.e. consuming respired CO2,
could not be fully excluded based on these data alone. Based on a natural
labelling experiment of a C3/C4 crop change introduced on one of
the soils 23 years before sampling and based on a free-air CO2
enrichment experiment with labelled CO2 on another soil, a turnover
time of ca. 18 years has been estimated for branched GDGTs in these arable
soils. |
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