Succession and the Development of Alluvial Communities After a Flood in 1997

This paper details a ten-year period in the development of floodplain biotopes after a disastrous flood in 1997 at three sites on along the Spojená Be va River in the Zlín and Olomouc regions, Czech Republic. Two of the sites are located on gravel bars, whilst the third site is located on a bank characterized as bare bed flysch sediments uncovered after a flood in 1997. After the flood, the previously homogeneous alluvial environment changed into a varied mosaic of biotopes with renewed conditions for the development of willows (Saliceta fragilis inferiora) and stands of Ulmi-fraxineta carpini superiora and Alni glutinosae-saliceta superior. A detailed study of the vegetation at the selected sites was conducted annually from 1998-2002, and in 2008, using 10 m wide transects oriented perpendicular to the river. The obtained data, including phytocoenological records, were compared with the vegetation communities ten years earlier and during the examined time interval. The dependence of particular types of biotopes on site conditions was described. In total, we identified and located 14 types of biotopes, completed 58 relevés, and found 245 species. The results show that succession is faster at moist sites with fine sediment in Rybá e and slower at drier sites without fine sediment in Lhotka nad Be vou and Choryně. The flooding of the floodplain forest was not destructive for most species outside the flood channel. Between 2004 and 2006, short-lived and segetal species retreated. The dominant species are Phalaris arundinacea, Urtica dioica, Echium vulgare, and Artemisia vulgaris. Invasive neophytes included Reynoutria japonica, Solidago canadensis, Impatiens glandulifera and Robinia pseudoacacia. The results obtained through this project can serve as a valuable foundation for decisions regarding nature conservation.