Holocene environmental events in the Viitna area, north Estonia

Abstract

Holocene vegetation dynamics of the Viitna kame field is discussed. Replacement of birch woods which dominated in the area at the beginning of the Holocene by mixed and broadleaved forest took place at c7600 BP, showing some delay in comparison with the other newly studied sites of Estonia. The elm decline at 4700 BP occurred earlier than the general opening up of the area and possible pastoral farming which began c4000 BP. AT 3300 BP, the first cereal pollen appears and the arable farming is suggseted in the surroundings of the kame field. The kame field differs from the other parts of coastal Estonia in a low share of pine trees in forests. Hence, these forests were less vulnerable to fires, especially in the Early Holocene. Pine became and important component in the forest composition rather late, during the alst 1500 yr. Lake-level fluctuations in four investigated lakes (Viitna Lina- and Pikkjarv, Nabudi, and Vohnja Koverjarv) were reconstructed mostly on the basis of changes in the sediment composition at least on one transect and aquatic pollen. All the studied lakes had the lowest water level between 5400-3700 BP, which was 3-4.5m lower than at present. This regional lowering was caused by the groundwater table drop due to the formation of the Loobu Riber. The pollen-based climate reconstruction shows a rapid warming and an increase in humidity at the end of the Pre-Boreal. Climate deteriorated between 8700-8500, 7900-7700, 2000-1000, and 500-300 BP. Shifts to wetter conditions appeared at 9200-8800, 7800-7600, 6500-6300, 5800-5200, 4600-3900, 2400-1600 and 800-600 BP.