We investigated sediments of three Sphagnum peatland-lake ecosystems located in Tuchola forest, both in moraine (Małe Leniwe near Rekowo) and outwash plain (Dury and Rybie Oko) landscape. Geological cross-sections were studied for each basin. Characteristic feature of these ecosystems is the presence of floating mats encroaching the lakes and deposition of highly hydrated sediments below the floating mat. Principal conditions favouring the development of peatland-lake ecosystems are (1) location of the lake in a sandy, non-calcareous catchment overgrown by coniferous forest, (2) steep ness of the lake basin, what prevents emerged macrophytes succession and (3) the depth of the basin significantly exceeding 10 m to avoid complete in filling of the lake basin. The developmental pathway in the Dury I basin indicates a shift in lake environment from neutral to acid one. After initial development of Charophytes, Potamogeton and Najas expanded, which later on, were succeeded by Sphagnum due to acidification of the lake water. Initial stages of the development of the lakes were determined mainly by allogenic factors, whereas in later stages autogenic factors (development of floating mat and peat acidifying the lake water) played fundamental role.

This paper presents the Late Glacial stage of the development of the Białe Ługi peatland in the southern Holy Cross Mountains, based on a comprehensive palaeoenvironmental data. A complex analysis of palynology, Cladocera, sed imentology, geochemistry and 14C dating were used. Organic deposition was initiated during the Oldest Dryas. The sedimentary record of the aquatic and terrestrial ecosystems reflects considerable difference between cooler (Oldest, Older and Younger Dryas) and warmer phases (Břlling and Allerřd). Periods of intensified interaction between aeolian processes and peatland are related to stages of disappearing vegetation and changes in aquatic invertebrate communities. We therefore suggest that peatlands were created as a result of local lithological-structural, tectonic, hydrogeological and morphological conditions, and the peatland development rate was largely influenced by changing climatic conditions, which determined local vegetation development, intensity of denudation processes and water level changes. The results validate significance of selection and use of several methods, as well as value of biogenic deposits from the Białe Ługi peatland as archives of past climate change in the Małopolska Upland. Relatively stable water conditions and uninter rupted biogenic sedimentation in the Late Glacial that were provided by the geological structure and relief suggest the studied peatland is a leading one in the region.