Lake Records of the Vegetational and Climatic History of Southwestern Siberia

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This proposal requests support for a study of a large cluster of lakes of glacial origin occurs north of Aktash (50 20' N, 87 35' E) in the Altai Mountains of southwestern Siberia. They are located in large unforested areas at elevations of about 2000 m with conifer forest extending on adjacent ridges up to tree line above 2200 m. The lake sediments will be cored to determine by pollen analysis the vegetational and climatic history of this little known area. Included in the study will be cores from two other lakes in the mountains and one in the plain near Tomsk, obtained during exploratory field work in 1998. The focus in both the mountains and the plain is on the history of the steppe/forest border, an ecotone of proven sensitivity to climatic change as revealed by pollen analysis. In a second area northeast of the Altai Mountains in the steppe region of Khakassia (55 N, 90 E), at elevations about 200 m in a basin of the Yenesei River, the bordering ridges contain forest steppe characterized by birch and larch, with taiga conifers at elevations above about 750 m in the adjacent mountains. Fluctuations of these major ecotones will he determined by stratigraphic pollen analysis of lake sediments. Lake waters in the steppe range from fresh to saline, and their salinity history as determined by diatom analysis of their sediments will supplement pollen analysis for the reconstruction of the climatic history, for diatoms can sensitively record changes in salinity over time, as has been shown especially by extensive studies in the North American Great Plains.