CONFERENCEFloating Lake Nut (Trapa natans) - A Witness of Natural and Human History in Latvia
Laimdota Kalnina
University of Latvia, Faculty of Geography and Earth Sciences
Aija Cerina
University of Latvia, Faculty of Geography and Earth Sciences
Iveta Zvagina
University of Latvia, Faculty of Geography and Earth Sciences
Ineta Grine
University of Latvia, Faculty of Geography and Earth Sciences
DOI: 10.22364/fg.16.1
Keywords: Interglacial period, Holocene, Trapa natans, Pollen, Stone Age
Abstract
Floating Water-nut Trapa natans in the territory of Latvia grows in the area of its northern distribution and is a protected plant. At the beginning of the 40s of 20th century were known 10 deposits of Water-nut fossil fruit, now their number with fossil fruit and pollen deposits has grown to 27. Fossils Trapa natans have been found not only in the Holocene but also in the Pleistocene interglacial sediments. Map of the current distribution of floating Water-nut and sites of fossil finds in Latvia has been prepared. Palaeobotanical studies of lake sediments allow to conclude that floating Water-nut has grown in many lakes since the second part of the Holocene climatic optimum. In the Pokrata Lake and Priekulanu Lake the floating Water-nut still grows and the number of pollen and fossil fruit finds is variable, but nowadays number of them is similar to what it was shortly after its introduction into the lake. Research on Pokrata Lake indicates that a significant reduction or even disappearance of floating Water-nut pollen has occurred several times, but the latter may be attributed to the "Little Ice Age" during the Middle Ages. In different years observations of the existing sites have been repeated, which allows to conclude that the population of Trapa natans in Pokrata and Priekulanu lakes is not on the verge of extinction, but on the contrary - it is improving.