Butomus umbellatus-community in the Czech and Slovak Republics

Stands of Butomus umbellatus L. and their habitat characteristics were studied in the Czech and Slovak Republics in order to distinguish the Butomus umbellatus-community from other littoral vegetation and clarify the ecological causes of its formation and development. Ward's method of cluster analysis was used as a basis for phytosociological classification or the stands with dominant B. umbellatus; the chemical soil characteristics of habitats of Butomus umbellatus-community we retreated by PCA. Cyclic changes or water level are the main factor encouraging the development of the community. Stands of B. umbellatus are usually species-poor and may be classified as Butomus umbellatus-community in a broad sense. A great proportion of the phytosociological relevés obtained represent heterogeneous stands formed by a mixture of species; they are transitional types of open water communities and littoral vegetation. This reflects the situation in natural habitats or B. umbellatus: the changes in vegetation follow those in water level and numerous stands occur in man-influenccd or disturbed habitats.