In this paper, the evaluation of long-term stationary research (1990 – 2016) on a floodplain forest stand Čunovo, near Bratislava, is described. The area is affected by hydropower water structure Gabčíkovo on the Danube river. In the first years of monitoring, the crop of Salici–Populetum was degradated due the presence of nitrophilous and mesophilous species. A dynamic changes in species composition, diversity, live forms and physiognomy have taken place affected by changed hydrological regime, an increase of groundwater level surrounding the Čunovo reservoir. During the quarter the softwood floodplain forest changed to a wetland-type permanet marsh.