Leaf wax <i>n</i>-alkanes in modern plants and topsoils from eastern Georgia (Caucasus) – implications for reconstructing regional paleovegetation
<p>Long-chain <i>n</i>-alkanes originate from leaf waxes of higher terrestrial plants, they are relatively resistant against physical and chemical degradation and are preserved in sediment archives for at least millennial timescales. Since their homologue patterns discriminate b...
Main Authors: | , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2018-06-01
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Series: | Biogeosciences |
Online Access: | https://www.biogeosciences.net/15/3927/2018/bg-15-3927-2018.pdf |
Summary: | <p>Long-chain <i>n</i>-alkanes originate from leaf waxes of higher terrestrial
plants, they are relatively resistant against physical and chemical
degradation and are preserved in sediment archives for at least millennial
timescales. Since their homologue patterns discriminate between vegetation
forms, they were increasingly used for paleovegetation reconstructions during
the last years. However, before any robust interpretation of the long-chain
<i>n</i>-alkane patterns in sediment archives, reference samples from modern
vegetation and topsoil material should be investigated at a regional scale.
Apart from some temperate and tropical regions, such systematic regional
studies on modern plant and topsoil material are still largely lacking.</p><p>To test the potential of leaf wax-derived <i>n</i>-alkane patterns for
paleoenvironmental studies in the semi-humid to semi-arid central southern
Caucasus region, we investigated the influence of different vegetation forms
on the leaf wax <i>n</i>-alkane signal in modern plants and topsoil material
(0–5 cm) from eastern Georgia. We sampled (i) sites with grassland/herbs
that included steppe, cultivated grassland and meadows, and (ii) sites that
are dominated by deciduous hornbeam forests.</p><p>The results show that long-chain <i>n</i>-alkanes originate from leaf waxes of
higher terrestrial plants and that their homologue pattern allow to
discriminate between different vegetation forms: <i>n</i>-Alkanes derived from
sites with grassland/herbs are mainly dominated by C<sub>31</sub>, while
<i>n</i>-alkanes derived from sites with deciduous trees/shrubs show high
abundances of C<sub>29</sub>. Thus, long-chain <i>n</i>-alkanes have a great
potential when used for regional paleovegetation reconstructions. Moreover,
the <i>n</i>-alkane distributions of the topsoils do not show correlations with
mean annual temperatures and precipitation along the investigated transect.
As degradation of organic matter can affect the leaf wax <i>n</i>-alkane
distribution, we further present an updated end-member model that includes
our results, accounts for degradation effects and enables semi-quantitative
reconstructions of past vegetation changes in the central southern Caucasus
region.</p> |
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ISSN: | 1726-4170 1726-4189 |