Impoverishment of recent floodplain forest mollusc fauna in the lower O hře R iver ( C zech R epublic) as a result of prehistoric human impact

Analyses of fossil mollusc successions have rarely been used to study the development of floodplain forests during the H olocene. The O hře R iver, located in a prehistorically settled chernozem area in the C zech R epublic, is partly situated in C retaceous marlstones, yielding sediments suitable for fossilization directly in floodplain deposits. We analysed five fossil mollusc successions situated in the lower stretch of the O hře R iver and compared the results with recent mollusc assemblages studied along the entire 256 km of the river. Fossil samples were composed mostly of open‐country species throughout the H olocene or the whole preserved succession. Only some samples also contained woodland assemblages, but these were always greatly impoverished, with a very low frequency of strictly woodland species. Although the natural‐looking appearance of the present‐day floodplain forests of the lower river stretch has resulted in its being declared a nature reserve, modern floodplain forest mollusc assemblages there are also impoverished. This reduction in the distribution of strictly woodland species compared with modern assemblages in the upper stretch of the river seems to be the result of an ancient human settlement and continuous disturbances of the floodplain forest development since the N eolithic. Thus, fully developed floodplain forest assemblages occur recently only in the upper non‐impacted stretch of the river. Based on the studied fossil successions we can conclude that the lower O hře R iver floodplain was probably a mosaic of open and disturbed forest habitats throughout the H olocene. This area is part of a central E uropean landscape island, where forests probably never fully developed and open patches from the early H olocene continually developed into an agricultural landscape.