ИСТИНА

The reconstruction of peatland developing processes is based on radiocarbon dating of lowermost peat horizons and plant macrofossil analysis of peat samples from 40 mires in the Meshchera lowlands (the central part of the East European Plain). The landscape of this region are formed on thick fluvio-glacial sands and characterized by flat relief, high level of ground water and large areas of pine forests and numerous mires. This area is belongs to so-called Polessye-type of landscapes. All studied peatlands are located on watersheds and high river terraces and formed by forest paludification. Phases of peatland initiation were compared with Holocene fire regime revealed from macro-charcoal data and climatic reconstructions available for this area. The obtained results showed that the peatland developing process of these areas took place throughout the Holocene. The ages of basal peat samples showed that the majority of the studied peatlands formed between 9000 and 6000 cal yr BP, during the Holocene thermal maximum. The highest number of mires formed between 7600 and 6000 cal yr BP. The second period of active paludification ranged between 3700 and 3200 cal yr BP. According to climatic reconstruction this period was characterized by increased temperatures and driest conditions entire the Holocene and high fire frequencies. The last phase of peatland initiation was between 1500 and 1700 cal yr BP and was coincided with increase of human induced forest fires during occupation of the area during the Early Iron Age. During the climatic cooling and increase of humidity in periods between 5000 and 4000 cal yr BP and 3000 and 2000 cal yr BP the lowest number initiated. In contrast to the areas located in the taiga zone, where the active peatland growth correlated with wetter and cooler epochs, in the Meshchera lowlands the stages of paludification coincided with phases of dry and warm climatic conditions and the increase in the frequency and intensity of fires. Obviously, the peatland formation process in these areas was influenced by the fire regime of the territory. After severe forest fires, accompanied by the death of the forest stand, the water balance of the study area was changed by reducing evaporation and increasing surface runoff, which led to the waterlogging of the territory. According to the plant macrofossil analysis of peat, all studied peatlands were in the eutrophic stage of development during the entire Holocene. The transition to mesotrophic conditions in different mires ranged from 1400 to 400 cal yr BP. It is possible that periodic fires and burning of peat deposits contributed to the supply of nutrients to the peatland ecosystems and provided eutrophic habitat conditions.