Elena M. Volkova

A multi-proxy record of Holocene environmental change, peatland development and carbon accumulation from Staroselsky Moch peatland, Russia:

Despite their huge extent, the peatlands of Russia are an under-exploited source of data on palaeoenvironmental change. We investigated the Holocene history of Staroselsky Moch, an ombrotrophic peatland in the Tver Region of European Russia by analysis of testate amoebae, peat physical properties, plant macrofossils and pollen. The peatland developed through a classic hydroseral succession in the early Holocene with a sharp decline in mineral input to 6200 cal. BC followed by an abrupt transition from fen to bog vegetation around 5500 cal. BC. Through the Holocene, the peatland has accumulated carbon at a mean apparent rate of 21.5 g C m−2 yr−1 suggesting that carbon accumulation rates in peatlands of European Russia lie close to the global average, and contrasting with a short sequence of eddy-covariance data which implies a net loss of carbon. The testate amoeba record shows considerable variability which may be driven by climate, but changes are not well replicated in the macrofossil or pollen data. We tentatively infer (1) a phase of early Holocene warming commencing around 7200 cal. BC, (2) dry peatland surface conditions c. 3700–3900 cal. BC, (3) a shift to wetter conditions from c. 3900 cal. BC, and (4) drier conditions from c. 400 cal. BC onwards. More robust and precise hydroclimatic reconstructions for this region will require the development of a regional transfer function and the replication of results between cores and sites.

Growing season variability of net ecosystem CO2 exchange and evapotranspiration of a sphagnum mire?in?the?broad-leaved forest zone of European?Russia

The spatial and temporal variability of net ecosystem exchange (NEE) of CO2 and evapotranspiration (ET) of a karst-hole sphagnum peat mire situated at the boundary between broad-leaved and forest‐steppe zones in the central part of European Russia in the Tula region was described using results from field measurements. NEE and ET were measured using a portable measuring system consisting of a transparent ventilated chamber combined with an infrared CO2/H2O analyzer, LI-840A (Li-Cor, USA) along a transect from the southern peripheral part of the mire to its center under sunny clear-sky weather conditions in the period from May to September of 2012 and in May 2013. The results of the field measurements showed significant spatial and temporal variability of NEE and ET that was mainly influenced by incoming solar radiation and ground water level. The seasonal patterns of NEE and ET within the mire were quite different. During the entire growing season the central part of the mire was a sink of CO2 for the atmosphere. NEE reached maximal values in June‐July. 6:8 4:2 mol m 2 s 1 /. The southern peripheral part of the mire, due to strong shading by the surrounding forest, was a sink of CO2 for the atmosphere in June‐July only. ET reached maximal values in the well-lighted central parts of the mire in May (0:34 0:20 mm h 1 ) mainly because of high air and surface temperatures and the very wet upper peat horizon and sphagnum moss. Herbaceous species made the maximum contribution to the total gross primary production (GPP) in both the central and the peripheral parts of the mire. The contribution of sphagnum to the total GPP of these plant communities was relatively small and ranged on sunny days of July‐August from 1:1 1:1 mgC g 1 of dry weight (DW) per hour in the peripheral zone of the mire to 0:6 0:2 mgC g 1 DW h 1 at the mire center. The sphagnum layer made the maximum contribution to total ET at the mire center.0:25 0:10 mm h 1 / and the herbaceous species on the peripheral part of the mire (0:03 0:03 mm h 1 ).

Vegetation dynamics and fire history at the southern boundary of the forest vegetation zone in European Russia during the middle and late Holocene

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 broadleaved forest zone in the east-central 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 precipitation–evapotranspiration 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 broadleaved 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 because of harvesting of broadleaved trees and contributed to the formation of the current mixed coniferous broadleaved forests.

Autogenic and allogenic factors affecting development of a floating Sphagnum-dominated peat mat in a karst pond basin

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.

Holocene Dynamics of Vegetation and Ecological Conditions in the Center of the East European Plain

Changes in the vegetation and fire regimes in the central East European Plain during the second half of the Holocene have been reconstructed based on the results of paleobotanical analysis and radiocarbon dating of material from a section of peat deposit in the Mordovia State Nature Reserve. It has been shown that birch–pine forests were widespread in the region between 7000 and 5000 yr BP, with the frequency of fires in that period being high (the fire return interval ranged from 10–20 to 100 years). Beginning from 5000 yr BP and to the early 20th century, broadleaf forests were dominant, with the fire return interval increasing to 300–500 years or longer.