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| Titel |
Hydrological conditions determine branched glycerol dialkyl glycerol tetraether distributions in soils of the Iberian Peninsula |
| VerfasserIn |
Carme Huguet, Johanna Menges, Susanne Fietz, Dirk Sachse, Antoni Rosell-Melé |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250074691
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| Zusammenfassung |
| Temperature is one of the key environmental factors driving climate change, but past
continental temperature records are constrained by the few proxies that can be applied in
these environments. The MBT-CBT proxy is based on the distribution of branched glycerol
dialkyl glycerol tetraethers (brGDGTs), bacterial membrane lipids in soils1.Since the degree
of cyclisation of the GDGTs (CBT) was found to corellate to soil pH, while tindex degree of
methylation (MBT) corellates to mean annual temperature and soil pH. a combination of
these two indices allows the estimation of mean annual temperature (MAT). However,
it has been suggested, that other factors such as the hydrological conditions can
also influence the MBT2, although it has never been testet directly. To asses the
effect of hydrological conditions on the MBT-CBT a set of 25 soil samples of the
Iberian Peninsula covering a temperature range from 10-18ºC and a wide range of
hydrological regimes was analysed (405 mm to 1455 mm per year) . We found that CBT
was significantly correlated to soil pH confirming it even at a regional scale as a
robust proxy for soil pH. The MBT was also shown to relate to soil pH, but the the
expected relation between MBT and MAT could not be established. In fact, the
correlation between MBT and MAT was inverse to the one expected according
to previous studies and presented large scatter (R2=0,2). Consequently the MAT
estimation using the MBT-CBT proxy leads to an underestimation of MAT, which
is most prominent at the dryest sites and reaches up to 24ºC. Instead we found a
significant correlation between MBT and annual mean precipitation as well as the
Aridity Index (AI)3, a parameter quantifying water availability in soils. This suggests
that in dry environments or under moisture shortage the influence of the degree of
methylation of branched GDGTs is not coupled to temperature but to the degree of water
availability.
1. Weijers, J.W.H. et al. 2007. GCA. 71, 703-713.
2. Peterse, F., et al. 2012, GCA. 96, 215, 229
3. Trabucco, A., and Zomer, R.J. 2009. http://www.csi.cgiar.org |
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