SUBREGIONAL VEGETATION FORMATION PATTERNS IN THE SOUTH OF EASTERN SIBERIA IN THE MID- TO LATE HOLOCENE
E.V. Bezrukova1, S.A. Reshetova1, E.V. Volchatova1, N.V. Kulagina2, A.A. Shchetnikov2, M.A. Krainov1, I.A. Filinov2
1Vinogradov Institute of Geochemistry, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
2Institute of the Earth’s Crust, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
Keywords: Holocene peatlands, lacustrine sediments, palynology, dated records of the natural environment, vegetation dynamics, Baikal region
Abstract
This article presents results from reconstructing vegetation in the south of Eastern Siberia along the meridional profile passing through paleogeographically poorly studied subregions: Khandinskaya depression, the south of the Angara-Lena plateau, and the middle mountain taiga belt of the Oka plateau (Eastern Sayan). Patterns and features of subregional and local vegetation development in the Mid- to Late Holocene have been established. The metachronism of maximum development of taiga vegetation, which underlines the determining role of subregional climatic factors in the transformation of the regional climate of the Holocene, has been revealed in the subregions under study. It is suggested that the depth of penetration of permafrost may be one of the determining factors limiting the synchronous spread of arboreal plants, delaying it for several centuries compared to subregions lying outside the permafrost zone. It is shown that in the subregions under study, the regularity in the reconstructed biome dynamics is a gradual expansion of the forest biome and a reduction of the tundra biome. The role of the steppe biome in the low-mountain subregions turned out to be insignificant, while in the middle-mountain subregions of the Oka plateau it is becoming more significant. Pollen records show the formation of secondary birch forests both in the Khandinskaya depression and in the south of the Angara-Lena plateau during the last millennium, which should be regarded as the onset of the anthropogenic influence of forest fires or deforestation on subregional vegetation. No distinct indicators of human activity within the watershed of Lake Sagan-Nur (Oka plateau) have been detected. A comparison of the reconstructed dynamics of the forest biome from the subregions under study with the climatic records of the northern hemisphere during the Mid- to Late Holocene showed that a gradual expansion of the forest biome followed a decrease in the continentality of the climate in the northern hemisphere, which is evidenced by a decrease in summer and an increase in winter insolation.
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