Origin and development of mire formation process in West-Siberian plain
The researches date the origin and development of mire formation in West-Siberian Plain back to the Holocene and, according to M.I. Neyshtadt, it is 10-12 thousand years old. The most ancient peatland on the territory of Western Siberia is 9900±100 years old. M.I. Neyshtadt traced the rate of mire formation process by example of the peat moss mire Bakcharskoe. According to this result the reduction of mire formation area is noted for the last 2000 years. It is connected with the spreading of most mires on the adjoining territory. Originally, Bakcharskoe mire was a system of small independent mires, which in the Holocene became a single mire with the area of about 2.3 thousand km <sup>2</sup>. Such regularity is typical for the whole territory of West-Siberian plain. The peat gain for the entire period of the Holocene by the results of absolute dating of the lower and upper bounds of layers of peat deposits of the corresponding power is considered. The maximum size of linear speed of peat accumulation in the Holocene is established for mire systems of subtaiga (1.1 mm/year). In the southern, which belongs to the zone of excess moistening, the intensive peat accumulation is caused by more favorable climatic indicators and rather high biological efficiency of biogeocenoses of pine suffruticous-sphagnous type (raised bogs). In the southern taiga the exception is only low indicators of linear speed of peat accumulation (0.3-0.36 mm/year) in buried Holocene peat bogs in valleys of the rivers where there was a strong pressing of peat thickness. Comparison of results of activity of peat accumulation with the climate of Western Siberia in the Holocene is carried out. Natural evolution of mires is considered. Now mire formation process as a whole has slowed down. Processes of natural bogging are most active on the periphery of mire systems. As S.V. Vasilyev notes, during the modern period the minimum peat accumulation is observed in the North and maximum - in the south. In Western Siberia its speed can be higher - 0.9 mm/year.