|
|
Changes in nutrient availability imprinted in long-term diatom succession in lakes
Tichá, Anna ; Kuneš, Petr (advisor) ; Magyari, Enikő Katalin (referee) ; Catalan, Jordi (referee)
An examination of primary production in lakes shows regular trends during the Late Glacial and the Holocene periods: an increase ('eutrophication') and a decrease ('oligotrophication') usually connected with the input of terrestrial organic matter ('dystrophication'). Although nutrient availability usually influences production, other abiotic and biotic factors enter lakes' complex ontogeny, such as light availability, mixing regime, pH level, mechanical disturbance, predation or competition. Consequently, the past relationship between nutrient availability and primary production contains important information about the drivers of ecosystem functioning in the past. The reconstruction of past processes relies on the sensitive response of aquatic organisms to environmental changes. Their subfossil remains record the dynamic processes in the sediments and reveal both the local lacustrine history and more global events. Among other organisms, diatoms fulfil their function as a valuable proxy of past physical and chemical properties of water bodies. Whereas the record of planktonic diatom species dynamics represents the general ecosystem condition, variations in species-rich littoral periphytic diatoms add necessary insight into finer environmental fluctuations. The presented research combines...
|
|
|
Environmental gradients during Late Glacial in Central Europe
Petr, Libor ; Sádlo, Jiří (advisor) ; Magyari, Eniko (referee) ; Roleček, Jan (referee)
The Lateglacial and Early Holocene are key periods with respect to the understanding of the present-day vegetation and environment. An interdisciplinary approach is important for the study of these changes. Only by interlinking biological and geoscience evidence can we obtain a more comprehensive picture of this key period. It is not possible to interpret any pollen spectrum in the sedimentary record without knowledge of the history of the locality and its vicinity. Rapid climate changes had a crucial effect on the environment and vegetation. Continentality of the climate and a deficit of precipitation amplify the effect of local conditions. Vegetation, as in the case of vertebrates and molluscs, comprises a combination of species of a continental steppe, mountain biotopes and disturbed habitats. This facilitated contact among species and populations that are biogeographically separated at present. Vegetation of the Lateglacial period in the Czech Republic ranges in character from frost barrens in the mountains, through steppe-tundra vegetation at medium altitudes to a continental steppe in the lowlands and pine woodlands constrained to a moist floodplain. The Western Carpathians were covered by a taiga. In the Pannonian Lowland, there were open forests with conifers and broadleaved woody plants....
|
guest ::
