The vegetation cover response in the Eastern Sayan Foothills to the Holocene climate extremes (the Bolshoye Peat Bog case study)

Article provides the results of palaeoecological reconstruction of vegetation cover changes and climatic conditions at the foot of the Eastern Sayan northwestern macroslope over the past 6600 years. The results are based on radiocarbon AMS dating, pollen, macrofossils, NPP, macrocharcoal and testate amoebae analyses of peat deposits from Bolshoe bog situated on the Yenisei River right bank. It was established that the waterlogging process was initiated by the pyrogenic factor. During the last approximately 6000 cal. a BP dark coniferous forests with a dominant position of Pinus sibirica were common in the foothills. The change in climatic conditions towards decreased moisture availability 4050–3600 cal. a BP contributed to the lower border of dark conifers rise and the strengthening of forest-steppe communities with Betula sect. Albae. This period is characterized by the most dramatic transformations. Less prolonged periods of forest lightening occurred in 3170–3080, 1850–1720, 490–400 and 310–220 cal. a BP, when the taiga and cold deciduous forest biomes were of almost equal importance. The most significant expansion of the dark conifers range began 1600 cal. a BP and reached a maximum 1350–1230 cal. a BP, which can be correlated with Dark Ages Cold Period. Based on the macrocharcoal analysis results six stages of increased fire activity were identified: 6500–6300, 4300–3600 (includes 4 fire episodes, characterized by the shortest fire intervals), 3400–2800, 1800–1550, 1200–1000, and from 150 cal. a BP to present. Based on a multy-proxy analysis, periods of increased moisture were established: 6300–5320, 4700–4200, 3080–2900, 2820–2390, 1720–1230, 400–310 and 130–70 cal. a BP. The decreased moisture was characteristic of the intervals 5320–4960, 4050–3600, 2390–2220, 1000–700 and 30–10 cal. a BP.

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