Quaternary pollen and DNA analysis

Holocene climate and vegetation dynamics

Enikő Magyari's research focuses on the last glacial and Holocene vegetation dynamics of Hungary and SE Europe. Current projects include the investigation of ecosystem response to rapid climate changes in the SE Carpathians and the palaeo-environmental record of Late Glacial and Holocene landscape transformations brought about by agriculture and pastoralism in two large river basins in Europe: the Tisza lowlands in E Hungary and the Maritsa lowlands in SE Bulgaria and NW Turkey. Research techniques include fossil pollen analysis, plant macrofossil analysis, microscopic charcoal analysis and ancient DNA analysis. In collaboration with other researchers the investigated lake and peat bog sediments are also subjected to radiocarbon, geochemical, testate amoebae, chironomid, cladocera and silicaceous algae analyses.

A new model of Holocene vegetation dynamics was developed for the Great Hungarian Plain, on the basis of a comprehensive study of palynological sections calibrated by 14C dating. Its key features are the following: 1) the central core of the Great Hungarian Plain was covered by wooded steppe throughout the entire Holocene, 2) a secular succession of cold and warm continental forest and steppe communities is now resolved at a millenial scale, and 3) new chronological boundaries are assigned to the traditional Holocene phases of vegetation history. Sampling and analytical work, 14C dating, and high-resolution multi-proxy analyses of palynomorphs and diatoms was focused on lake sediment profiles from two glacial lakes (Lake Bucura and Lake Taul dintre Brazi) in the Retezat Mts. (South Carpathians). Apart from the paleoecological studies, sediment samples were also prepared for planned oxygen isotope and other geochemical analyses, plant macrofossil and Cladocera studies. Paleotemperature reconstruction based on palynomorphs and chironomids yielded preliminary results.

Climate reconstruction based on research in the South Carpathians showed that glacial lakes experienced significant productivity increases at 14 500 and 11 600 ka, which follows warming events recorded in the Greenland ice cap by a lag time of 100–300 yr. The Younger Dryas cold event (12 800–11600 ka) exerted only negligible influence on the local cumulative heat flow. Tree line reconstructions allowed to infer a prominent increase in summer mean temperature in the Early Holocene.

Paleo-DNA analysis

In 2009, DNA samples from fossil and modern spruce were analysed to study the Holocene population genetics of and refugia for this tree. 11 000 year old pollen and cones were shown to contain characteristic chloroplast sequences, some of which no longer occur in modern populations. During the last glacial maximum, several smaller refugia of spruce (nunataks) may have existed in the Retezat Mts. Through multiple cycles of population growth and decrease, genetic drift led to the disappearance of rare alleles. Modern populations are not direct descendants of the refugium populations. Ecosystem response to rapid Late Pleistocene and Early Holocene warming phases were studied in the South Carpathians. A quantitative climate reconstruction showed no lag time in the regional vegetation response, which was proved to be coeval with the warming episodes at 14500 and 11550 cal BP, as established from the oxygen isotope signal in the Greenland ice core record. The response of lacustrine productivity and pedogenesis, however, is delayed by 200–300 yr, possibly due to the cooling effect of the ice sheet. The shift of the tree line immediately followed the warming, thus spruce forests were established in the alpine zone already in the late glacial period.

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