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| Titel |
Distribution of branched glycerol dialkyl glycerol tetraethers in surface soils of the Qinghai–Tibetan Plateau: implications of brGDGTs-based proxies in cold and dry regions |
| VerfasserIn |
S. Ding, Y. Xu, Y. Wang, Y. He, J. Hou, L. Chen, J.-S. He |
| 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 ; 12, no. 11 ; Nr. 12, no. 11 (2015-06-01), S.3141-3151 |
| Datensatznummer |
250117954
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| Publikation (Nr.) |
 copernicus.org/bg-12-3141-2015.pdf |
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| Zusammenfassung |
| The methylation index of branched tetraethers (MBT) and cyclization ratio of
branched tetraethers (CBT) based on the distribution of branched glycerol
dialkyl glycerol tetraethers (brGDGT) are useful proxies for the
reconstruction of mean annual air temperature (MAT) and soil pH. Recently, a
series of 6-methyl brGDGTs were identified which were previously co-eluted
with 5-methyl brGDGTs. However, little is known about 6-methyl brGDGTs in the
Qinghai–Tibetan Plateau (QTP), a critical region of the global climate
system. Here, we analyze 30 surface soils covering a large area of the QTP,
among which 6-methyl brGDGTs were the most abundant components (average
53 ± 17% of total brGDGT). The fractional abundance of 6-methyl
brGDGTs showed a good correlation with soil pH, while the global
MBT'5ME calibration overestimates MAT in the QTP. We therefore
proposed a MBT5/6 index including both 5- and 6-methyl brGDGTs,
presenting a strong correlation with MAT in QTP:
MAT = −20.14 + 39.51 × MBT5/6 (n = 27, r2
= 0.82; RMSE = 1.3 °C). Another index,
namely IBT (isomerization of branched tetraether), based on carbon skeleton
isomerization of the 5-methyl to 6-methyl brGDGTs, is dependent on soil pH:
pH = 6.77 − 1.56 × IBT (n = 27; r2 = 0.74,
RMSE = 0.32). Our study suggests that changing the position of
methyl group of brGDGTs may be another mechanism for some soil bacteria to
adapt to the ambient pH change in addition to the well-known cyclization. |
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