Abstract. Vegetation and climate reconstruction in the forest–steppe of Mongolia is
still challenging regarding the pattern of forest and grassland distribution
during the Holocene. Different sediments containing paleosols and humic
layers provide geomorphological archives for landscape development in
Mongolia. n-Alkane and macro-charcoal ratios represent specific indicators to
distinguish the share between grasses and trees. In a preliminary study, we
investigated the applicability of these two paleo-proxies from soils for
vegetation reconstruction comparing different relief positions and site
conditions in the northern Khangai Mountains of Mongolia. n-Alkanes that are deposited from leaf waxes in the soil have the potential to indicate vegetation composition on a local scale. Depending on
site-specific environmental conditions, n-alkanes are subjected to different
degrees of microbiological decomposition, which is more intensive in soils
of dry steppe than of forests. Mongolian forests are often underlain by
permafrost that may reduce microbiological activity. In steppe soils, the
decomposition of n-alkanes increases the quantity of mid-chain n-alkanes that adulterate the biomarker proxy signal to indicate more forest share. Macro-charcoals in soils have a site-specific component, but additional eolian input of macro-charcoals from long-distance transport can provide a distinct proportion in
sediments. Thus, eolian influx of wood-derived macro-charcoal can dominate
the proxy signal at sites where trees were few or had never existed. Radiometric dating of several paleosols and humic layers has shown that
both proxies coincide as evidence for high grassland-to-forest ratios during the Early Holocene. By contrast, the proxy signals diverge for the Late Holocene.
For this period, n-alkanes generally indicate more grassland, whereas
macro-charcoals show increased wood-derived proportions. We imply that this
difference is caused by increased forest fires and simultaneously spreading
steppe area. A main portion of leaf waxes and charcoal particles in soils directly derive from the covering and nearby vegetation, whereas large lakes and glacier may receive these biomarkers from a larger catchment area. Thus, we conclude that soil archives provide proxies on a more local and site-specific scale than other archives do. Although the temporal resolution of soil archives is
lower than for the other ones, biomarker proxies for paleosols and humic
layer can be related to periods of distinct geomorphological processes.
Further investigations comparing the multi-proxy data of different
geomorphological archives are necessary to improve the paleo-ecological
reconstruction for landscape development in Mongolia.