Leaf wax n-alkane patterns and compound-specific δ13C of plants and topsoils from semi-arid and arid Mongolia

Struck, Julian; Bliedtner, Marcel; Strobel, Paul; Schumacher, Jens; Bazarradnaa, Enkhtuya; Zech, Roland

Leaf wax inline-formulan-alkane patterns and their compound-specific inline-formulaδ13C signatures are valuable proxies for paleoenvironmental reconstructions. So far, their potential has not been investigated in semi-arid to arid Mongolia. We have therefore analysed the leaf wax inline-formulan-alkanes and their compound-specific inline-formulaδ13C signature of five plant species (Poaceae, Cyperaceae, Artemisia spp., Caragana spp. and Larix sp.) and topsoils (0–inline-formula5 cm) along two transects in central and southern Mongolia.

Grasses show a distinct dominance of the inline-formulan-Cinline-formula31 homologue, whereas the shrubs Caragana spp. and Artemisia spp. are dominated by inline-formulan-Cinline-formula29. Larix sp. is characterised by the mid-chain inline-formulan-alkanes inline-formulan-Cinline-formula23 and inline-formulan-Cinline-formula25. From plant to topsoil, inline-formulan-alkane patterns show the potential to differentiate between grass-covered sites from those covered by Caragana spp. inline-formulan-Alkane concentrations and odd-over-even predominance (OEP) of the topsoils are distinctly influenced by mean annual temperature, mean annual precipitation and aridity, likely reflecting the degree of inline-formulan-alkane degradation and biomass production. In contrast, the average chain length (ACL) and the inline-formulan-alkane ratio (inline-formulan-Cinline-formula31n-Cinline-formula29+n-Cinline-formula31) are not affected by climatic parameters and, thus, are not biased by climate. The compound-specific inline-formulaδ13C signatures are strongly correlated to climate, showing a significant enrichment with increasing aridity, indicating the effect of water use efficiency. Our calibration results suggest that long-chain inline-formulan-alkanes and their compound-specific inline-formulaδ13C signatures have great potential to reconstruct paleoenvironmental and paleoclimatic conditions when used in sediment archives from Mongolia.

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Struck, Julian / Bliedtner, Marcel / Strobel, Paul / et al: Leaf wax n-alkane patterns and compound-specific δ13C of plants and topsoils from semi-arid and arid Mongolia. 2020. Copernicus Publications.

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