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Climate and human activity affected significantly the Eurasian on the forest vegetation zone through the Holocene. This paper presents new multi-proxy records of environmental changes at the southern boundary of the mixed coniferous-broadleaf forest zone in the eastcentral part of the East European Plain during the middle and late Holocene. Palaeoecological analyses of a peat core for pollen, charcoal, peat humification, plant macrofossils and testate amoebae with dating using radiocarbon have shown that climate appears to have been a dominant control on vegetation. There is strong evidence for a reduced precipitationevapotranspiration ratio and high fire frequency during the Holocene thermal maximum (6.9-5.3 ka BP), leading to dominance of Betula-Pinus forests. By contrast subsequent climatic cooling led to the expansion of broadleaf forests and establishment of Picea. Human activities influenced vegetation from the Neolithic onwards but played a role which was secondary to climate until the recent past. Over the last century human impacts considerably increased due to harvesting of broadleaf trees and contributed to the formation of the current mixed coniferous-broadleaf forests.

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Lateral expansion of floating vegetation mats over the surface of aquatic ecosystems (terrestrialization) is one of the ways of peatland development. This process was commonly studied in kettle-hole lakes, whereas karst ponds have received less attention. We used a suite of palaeoecological analyses at Karstovoe mire (Mordovia, Russia) to reconstruct the formation of a floating Sphagnum-dominated peat mat over the karst pond. The results show that the floating peat mat had covered the central part of the pond by ca. AD 1600. Remains of Scirpus sp. and Calamagrostis sp. in the basal layers indicate that these plants might form a framework on which Sphagnum mosses and sedges were established. The terrestrialization could be triggered by the ‘Medieval Warm Period’ (AD 950–1250) as droughts reduce water levels and allow the pioneering plants to colonize exposed bottom sediments on the margins of lakes. Later, the development of the mire was mainly driven by autogenic factors that could be explained by the relatively stable hydrological regime in freely floating or poorly attached vegetation mats. In the mid 19th century, the surface wetness of the mire started to decline that can be related to both increased human activity associated with fires and to a greater thickness of the mat so that autogenic and allogenic effects were difficult to disentangle. In less than a century after that, the fen transformed to a pioneer raised mire. Our results show complex and context-dependent effect of autogenic and allogenic factors on the development of floating peat mats.