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.
Białowieża in Poland is a very famous region in Europe (because of its primeval forest and bison population), but its environmental history is poorly known. This article shows the results of palynological analysis, macrofossil analysis and geological settings of two mires in the Białowieża Forest. The pollen diagrams show changes of the vegetation cover from the younger part of the Late Glacial until the present time. The relative time scale is based on palynostratigraphy and comparison to published results of other sites from the adjacent regions. During the Late Glacial two stages of the vegetation succession were revealed: steppe and forest during the Alleröd period and tundra-like vegetation during the Younger Dryas. The Holocene history consists of five stages of plant cover development. The special features of the Białowieża Forest are conditioned by two main factors: low degree of anthropogenic impact and influences of continental climate and boreal zone, stronger than in the other regions of Poland.