Leaf waxes in litter and topsoils along a European transect

Abstract

Abstract. Lipid biomarkers are increasingly used to reconstruct past environmental and climate conditions. Leaf-wax-derived long-chain n-alkanes and n-alkanoic acids may have great potential for reconstructing past changes in vegetation, but the factors that affect the leaf wax distribution in fresh plant material, as well as in soils and sediments, are not yet fully understood and need further research. We systematically investigated the influence of vegetation and soil depth on leaf waxes in litter and topsoils along a European transect. The deciduous forest sites are often dominated by the n-C 27 alkane and n-C 28 alkanoic acid. Conifers produce few n-alkanes but show high abundances of the C 24 n-alkanoic acid. Grasslands are characterized by relatively high amounts of C 31 and C 33 n-alkanes and C 32 and C 34 n-alkanoic acids. Chain length ratios thus may allow for distinguishing between different vegetation types, but caution must be exercised given the large species-specific variability in chain length patterns. An updated endmember model with the new n-alkane ratio (n-C 31 + n-C 33 ) / (n-C 27 + n-C 31 + n-C 33 ) is provided to illustrate, and tentatively account for, degradation effects on nalkanes.

Late Quaternary climate and environmental reconstruction based on leaf wax analyses in the loess sequence of Möhlin, Switzerland

“…They analyzed samples from litter and two depths of the uppermost soil horizon. The results of the Schäfer et al (2016a) study are that (1) the chain lengths correlate significantly along the transect with the grassland and deciduous vegetation, (2) nalkanes from conifer forests show the understorey and (3) a correction for degradation of the n-alkanes is needed to get reliable information about the vegetation. n-Alkane patterns are thus a particularly valuable tool for the reconstruction of paleovegetation when pollen are absent, which is often the case in loess-paleosol sequences (LPS).…”

“…Nevertheless, grasses produce also n-alkanes in their leafs (Gao et al, 2012) and also show evaporative enrichment to some degree. In older publications, it has been stated that nC 29 is mainly produced by deciduous trees (Cranwell, 1973;Zech et al, 2010); the publication of Schäfer et al (2016a) shows that both nC 29 and nC 31 are more or less equally produced by grasses and shrubs. However, relative to nC 31 , Schäfer et al (2016b) state that deciduous trees produce more nC 29 .…”

“…Their homologue pattern depends on the type of vegetation (Cranwell, 1973;Marseille et al, 1999;Schwark et al, 2002) and can provide information about whether deciduous trees or grasses were dominant in the research area, whereas deciduous trees produce mainly n-C 27 and grasses predominantly n-C 31 and n-C 33 (Zech et al, 2010;Schäfer et al, 2016b;Schwark et al, 2002). Although controversy exists as to whether this approach can be used universally to reconstruct paleovegetation (Bush and McInerney, 2013;Wang et al, 2015), there is good evidence that leaf wax patterns can be used on a local (Schwark et al, 2002) and regional (Schäfer et al, 2016a) scale in Europe. Schwark et al (2002) investigated n-alkanes in a lake in southern Germany and found a remarkable accordance of pollen records and nalkanes.…”

“…Schwark et al (2002) investigated n-alkanes in a lake in southern Germany and found a remarkable accordance of pollen records and nalkanes. Schäfer et al (2016a) measured leaf wax patterns along a transect from southern to northern Europe in grasslands, deciduous forests and coniferous forests. They analyzed samples from litter and two depths of the uppermost soil horizon.…”

“…The odd-over-even predominance (OEP; Eq. 1) was calculated after Hoefs et al (2002) and is an indicator for degradation: values smaller than 5 are considered to be strongly degraded (Zech et al, 2010;Schäfer et al, 2016a) …”