LANDSCAPES AND CLIMATE OF THE BAIKAL REGIONIN THE LATE GLACIAL AND HOLOCENE(from results of complex studies of peat bogs)
E.V. Bezrukova, S.K. Krivonogov1, A.A. Abzaeva, K.E. Vershinin, P.P. Letunova, L.A. Orlova1, H. Takahara2, N. Miyoshi3, T. Nakamura4, S.M. Krapivina, and K. Kawamuro5
Limnological Institute, Siberian Branch of the RAS, 3 ul. Ulan-Batorskaya, Irkutsk, 664033, Russia
1United Institute of Geology, Geophysics and Mineralogy, Siberian Branch of the RAS,3 prosp. Koptyuga, Novosibirsk, 630090, Russia
2Kyoto Prefectural University, 1-5 Hangi-cho, Shimogamo, Sakyo-ku, Kyoto 606-8522, Japan
3Okayama University of Science, 1-1 Ridai-cho, Okayama, 700-0005, Japan
4Center for Chronological Research, Nagoya University, Chikusa, Nagoya 464-01, Japan
5Forestry and Forest Products Research Institute, Monoyama, Fushimi, Kyoto 612-0855, Japan
Keywords: Inshore peat bogs, Holocene, palynology, botanic composition of peat, short-term climatic changes, Holocene optimum, Baikal region
Pages: 20-33
Abstract
The paper presents results of complex studies of lacustrine and palustrine deposits from three boreholes drilled on the eastern and southern shores of Lake Baikal: data of palynological study and seeds and fruits analyses, botanic composition of peat, and AMS 14C age. The radiocarbon age is brought to conformity with the actual age by a calibration scale. The general features as well as the specifics of the vegetative-cover structure and climate at separate localities of the lake shore are considered for a period of >13 kyr, with a minuteness of 50-250 years. It is shown that from 13 to 9.3(8.5) kyr ago, the climate and vegetation underwent a series of short-term (200-1000 years) changes. In the first three periods of changes (13-10.3(9.5) kyr ago), the climate remained continental cold-temperature and insufficiently humid, and the vegetation was dominated by forest-tundra and tundra landscapes (mainly spruce, larch, and birch insular forests). In the next three periods (10.3-9.3(8.5) kyr ago), the continental climate became milder, and cedar pine and fir forests appeared. Later on, from 9.3(8.5) to ~6.9(5.5) kyr ago, the climate was continental humid-temperate, and the vegetation was dominated by dark-coniferous cedar pine and fir forests. The decrease in cyclone activity ~5.5 kyr ago might have been responsible for the reduction in the natural geographical range of dark-coniferous fir taiga. At the last stage of the vegetation evolution ~6.9(5.5)-0 kyr ago), the forests were dominated by cedar pine, larch, and pine. Analysis of the climatic and ecologo-edaphic factors determining forest plant spreading on different Baikal shores suggests the existence of two long-term optimal periods in the Holocene: humid (9.3(8.9)-6.9(5.5) kyr ago) and thermal (recent 5.5 kyr).
|
