Pollen diagrams, based on sediments from four small mires on the eastern summits of the Jeseníky Mts (the Praděd-Altvater group) in the Sudetes, the Czech Republic, show the development of vegetation in the area since the Subboreal period (ca 4700 B.P.). Stands of Corylus avellana with Picea abies and some Tilia cf. platyphyllos covered the eastern summits of the Jeseníky Mts between ca 5000 and 3000 B.P. Corylus avellana probably played the same role as Pinus mugo, common at similar altitudes in other Sudetes ranges. Between ca 3000 and 500–400 B.P. Picea abies, Fagus sylvatica and Abies alba dominated the natural precultural forests at the present alpine forest limit. An admixture of Acer (cf. pseudoplatanus) and Ulmus (cf. glabra) is very probable. Human impact (mountain summer grazing, hay making, selective beech cutting) influenced the summit vegetation and lowered the natural forest line from the beginning of the 17th century. The planting of spruce started at the beginning of the 19th century and is well expressed in the pollen diagrams. No traces of Pinus mugo, documented by Pinus sylvestris type of pollen or macroscopic material, were found.
The occurrence of hazel dormice on some islands in the Baltic Sea raises the question about the origin of these long isolated populations. The spread of hazel dormice from their Pleistocene shelters in southern Europe to the north was facilitated by a rapid spread of hazel during the Boreal after 10800 cal. yr BP and subsequently hazel dominated woodlands in central Europe. The immigration of the hazel dormouse from central Germany to Ruegen is not supported by findings and seems to be unlikely due to habitat fragmentation in the north-eastern German mainland. This is indicated by areas of poor sandy soils with poor pine forests besides wide and sandy river valleys and wetlands. In contrast, immigration via Denmark is rather possible considering the post-glacial development of the south-western Baltic Sea region. Especially the Darss Sill could have been used as a land bridge between south-eastern Denmark and north-eastern Germany about 9800 to 8800 cal. yr BP. A further migration of the species towards the east, e.g. to Bornholm, might be prohibited by the existence of the vast Oder River valley.