Last glacial vegetation reconstructions in the extreme-continental eastern Asia: Potentials of pollen and n-alkane biomarker analyses


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Bernhard.Diekmann [ at ] awi.de

Abstract

The current study presents quantitative reconstructions of tree cover, annual precipitation and mean July temperature derived from the pollen record from Lake Billyakh (65°17'N, 126°47'E, 340 m above sea level) spanning the last ca. 50 ka (ca. 50,000 cal yrs). The reconstruction of tree cover suggests presence of woody plants through the entire analyzed time interval, although trees played only a minor role in the vegetation around Lake Billyakh prior to 14 ka BP (<5%). This result corroborates low percentages of tree pollen and low scores of the cold deciduous forest biome in the PG1755 record from Lake Billyakh. The reconstructed values of the mean temperature of the warmest month 8-10 °C do not support larch forest or woodland around Lake Billyakh during the coldest phase of the last glacial between 32 and 15 ka BP. However, modern cases from northern Siberia, ca. 750 km north of Lake Billyakh, demonstrate that individual larch plants can grow within shrub and grass tundra landscape in very low mean July temperatures of about 8 °C. This makes plausible the hypothesis that the western and southern foreland of the Verkhoyansk Mountains could provide enough moist and warm microhabitats and allow individual larch specimens to survive climatic extremes of the last glacial. Reconstructed mean values of annual precipitation are about 270 mm during the last glacial interval. This value is almost 100 mm higher than modern averages reported for the extreme-continental north-eastern Siberia east of Lake Billyakh, where larch-dominated cold deciduous forest grows at present. This suggests that last glacial environments around Lake Billyakh were never too dry for larch to grow and that the insufficient summer warmth was the main factor, which limited tree growth during the last glacial interval. The nalkane analysis of the Siberian plants presented in this study demonstrates rather complex alkane distribution patterns, which challenge the interpretation of the fossil records. In particular, extremely low n-alkane concentrations in the leaves of local coniferous trees and shrubs suggest that their contribution to the litter and therefore to the fossil lake sediments might be not high enough for tracing the Quaternary history of the needleleaved taxa using the n-alkane biomarker method.



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Scopus/ISI peer-reviewed
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Published
Eprint ID
30553
DOI 10.1016/j.quaint.2012.04.007

Cite as
Tarasov, P. E. , Müller, S. , Zech, M. , Andreeva, D. , Diekmann, B. and Leipe, C. (2013): Last glacial vegetation reconstructions in the extreme-continental eastern Asia: Potentials of pollen and n-alkane biomarker analyses , Quaternary International, 290-29 , pp. 253-263 . doi: 10.1016/j.quaint.2012.04.007


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