Influence of water availability in the distributions of branched glycerol dialkyl glycerol tetraether in soils of the Iberian Peninsula
Menges, J. (Universität Potsdam. Institut für Erd- und Umweltwissenschaften)
Alcañiz, Josep M. (Josep Maria) (Universitat Autònoma de Barcelona. Departament de Biologia Animal, de Biologia Vegetal i d'Ecologia)
Fietz, Susanne (Stellenbosch University. Department of Earth Sciences)
Sachse, D. (Universität Potsdam. Institut für Erd- und Umweltwissenschaften)
Rosell Melé, Antoni (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)

Data:	2014
Resum:	The combined application of the MBT (degree of methylation) and CBT (degree of cyclization) indices, based on the distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in soils, has been proposed as a paleoproxy to estimate mean annual temperature (MAT). CBT quantifies the degree of cyclization of brGDGTs and relates to soil pH. MBT and the simplified version MBT' quantify the degree of methylation of brGDGTs and relate to MAT and soil pH. However, other factors such as soil water availability have also been suggested to influence MBT' and possibly restrict the combined application of the MBT' and CBT indices as a paleotemperature proxy. To assess the effect of hydrological conditions on MBT' and CBT, a set of 23 Iberian Peninsula soil samples, covering a MAT range from 10 to 18°C and a mean annual precipitation (MAP) range of 405mm to 1455 mm, was analyzed. We found that the CBT was indeed significantly correlated with soil pH in our sample set. In contrast, MBT' was not correlated with MAT but had a significant correlation with the aridity index (AI), a parameter related to water availability in soils. The AI can explain 50% of the variation of the MBT', and 70% of the residuals of MAT estimated with the MBT/CBT proxy as compared to instrumentally measuredMAT. We propose that, in arid settings, where water may be an ecologically limiting factor, MBT' is influenced by hydrological conditions rather than temperature. Thus, our results suggest that the combination of MBT' and CBT indices should be applied with caution in paleotemperature reconstructions in soils from dry subhumid to hyperarid environments.
Ajuts:	European Commission 252659 Ministerio de Ciencia e Innovación CGL2010-15000
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	Iberian Peninsula ; Soils ; MBT ; CBT ; Brgdgts
Publicat a:	Biogeosciences, Vol. 11 No. 10 (May 2014) , p. 2571-2581, ISSN 1726-4189

DOI: 10.5194/bg-11-2571-2014

11 p, 1.1 MB

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