ИСТИНА

Fire frequency was reconstructed on the base of macro- and micro-charcoal concentration in peat cores from five key areas, located in different landscape zone of European Russia: Ustyanskoe plateau in Archangelsk region (middle taiga), southern part of Valdai Upland (the Central Forest Biosphere Reserve, south taiga), Meshchera lowlands and Mordovia State Natural Reserve (Polessie-type landscape, mixed coniferous-broadleaf forests) and Mid-Russian Upland (Kaluzhskie Zaseki State Natural Reserve, broadleaf forests). The obtained results showed that the beginning of human occupation of the areas is clearly marked by increased fire activity. Medieval time (at about 1000 cal yr BP) and Modern Period (the last 300 years) were marked by high fire frequencies allover the East European Plain. In the model area "Kaluzhskie Zaseki" a significant increase in fire frequency was revealed around 2000 cal yr BP (Early Iron Age) and the maximum frequency of fires (8 fires per 1000 years) was reconstructed for the last millennium. However, periods of increased fire activity occurred prior to the occupation of these areas by human. The highest frequency of fire in all model areas was determined for the periods 9000-6000 cal yr BP and 3500 – 2500 cal yr BP. Acceding to data available, the influence of anthropogenic factor during these time interval was low. Archeological findings were not revealed in vicinity of the peat cores and no pollen or plant macrofossil indicators of human impact were detected. Evidently forest fires were coursed by climatic reason. According to regional climatic reconstruction inferred from pollen and testate amoebae data these periods were characterized by high temperatures and dry summer conditions. Even in the areas of spruce taiga forests (Ustyanskoe plateau and Valdai Upland) where fire events were rare entire the Holocene until the Modern Period, most of them occurred in 9000-6000 and 3500-2500 cal yr BP. In contract to the taiga area the Polesie-type landscapes (Meshchera lowlands, Mordovia, vast fluvioglacial plains with pine forests) were affected by repeated fires throughout the Holocene, nevertheless fire frequencies increased during the same periods as in other model areas. Fire-free interval determined for the periods 9000-6000 cal yr BP and 3500 – 2500 cal yr BP ranged from 15- 20 to 120 years.