Do hemicellulose biomarkers in soils reflect the 18O/16O isotopic composition of precipitation? Implications for a novel paleoclimate proxy

Mario Tuthorn1, Michael Zech1, Marc Ruppenthal2, Yvonne Oelmann2, Bruno Glaser3
1 LS Geomorphologie und Abt. Bodenphysik, Universität Bayreuth
2 Geographisches Institut, Eberhard Karls Universität Tübingen
3 Terrestrische Biogeochemie, Martin-Luther-Universität Halle-Wittenberg

P 2.13 in Loess and terrestrial archives

It is well known that δ18o of precipitation and of certain chemical compounds of plants depends on climate parameters. Therefore, we see large potential for a recently developed novel analytical method, the so-called compound-specific δ18o-analysis of monosaccharides for future paleoclimate studies (Zech, M. and Glaser, B., 2009. Rapid Communications in Mass Spectrometry 23, 3522–3532). In brief, the method is based on the extraction of plant-derived hemicellulose monosaccharide biomarkers (arabinose, fucose and xylose) from soils, derivatisation and finally δ18o analysis using gas chromatography-pyrolysis-isotope ratio mass spectrometry (GC-Py-IrMS).
In our here presented study we aim to answer the question “do hemicellulose biomarkers in soils reflect the 18o/16o isotopic composition of precipitation?”. We take advantage of an Argentinean climate transect, which reveals a systematic δ18o trend in precipitation ranging from –5‰ in the north to –11.7‰ in the south. Our results show that δ18o of soil hemicelluloses does not simply reflect the variability of precipitation. In fact, while δ18o of precipitation becomes more negative in the south, δ18o of all three investigated hemicellulose biomarkers become more positive. Given that the investigated climate transect is characterized by the transition from humid climate in the north to arid climate in the south (the so called “Arid Diagonal”), we conclude that hemicelluloses in soils do not simply reflect δ18o of precipitation but additionally are strongly influenced by the evaporative 18o enrichment of soil- and leafwater.

last modified 2012-07-26