Сибирский лесной журнал (Oct 2018)
Genesis and history of the post-glacial evolution of forest bog in the valley of the Dubches river
Abstract
The results of palaebotanical and radiocarbon study of the forest-bog ecosystem in the lower Dubches river are given in this paper. It was established that the paludification process of this area started in the late-glacial period and the Holocene, in the period from 14.4 to 9.5 thousand calendar years ago. The stratigraphic analysis of peat deposit of five profiles with different peat thickness has shown that the bog massif has formed due to the emergence of different bog parts and each of them has developed differently at the initial period. The peat deposit of profiles was formed by low-mire, mesotrophic and Sphagnum peats of forest-swamp and swamp subtype. The contemporary bog ground vegetation is presented by pine-dwarf shrub-sphagnum phytocoenosis (riam) with a well-developed tree layer of bog pine. The detailed stratigraphic analysis of deposit of a sample profile in the central part of the profile has shown that the succession series of bog phytocoenoses beginning from the late glacial period until now embraces 18 stages of changes. It was also stated that these changes are related to changing hydrological regime (humidity index variation (HI) from 2.1 to 7.8 is noted). Five development stages of bog vegetation have been revealed, which are closely connected with the humidity regime. The first stage lasted a short time, 14 400–13 356 calendar years ago. It was characterized by humidity index 7.8 and by dominating hyperhydrophilic hypnophytocoenoses. The second and third stages – 13356–2866 calendar years ago are characterized by humidity index 5.7–2.1 and by the development of eutrophic birch-rich-in-herbs and also birch phytocoenoses. The humidity index 7.3, as well as development of swampy Scheuchzeria phytocoenoses are characteristic of the fourth stage, 2866–1868 calendar years ago. The fifth stage, 1868 calendar years ago, – present time is characterized by humidity index 4.5–3.3, and by dominating fuscum phytocoenoses. The botanic peat analysis has shown three contact layers formed by birch peat which can be the evidence of xerothermal periods of the Holocene in the Near-Yenisei Siberia and afforestation of bog by birch tree stands. It was found that the average rate of vertical peat growth varied from 0.16 to 0.39 mm/year, i. e. much lower than peat accumulation rate in riams of middle taiga in the West Siberia.
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