A key challenge of conservation management in seminatural grasslands is to find ecologically cost-effective management regimes which will maintain the ecological functionality and biodiversity of a community. We studied changes in the plant functional trait composition and diversity of the flooded meadow in the 6-year field experiment in Soomaa National Park, Estonia. Five management regimes were introduced: traditional (cutting with a scythe and hay removal), mowing (machine cutting and hay removal), mulching (machine cutting without hay removal), spring burning and unmanaged control. Unmanaged and burned plots differed from cut plots due to their higher percentage of grasses and sedges, and of C-strategists, and by lower percentage of trampling- and grazing-tolerant species, erosulate species, and vegetatively mobile guerrilla species. Removal of litter enhanced rosette species and winter-green species. Traditional management increased the compositional variability among plots. Species richness remained almost constant in burned plots, and fluctuated in unmanaged plots, while in all cut plots there was a significant increase in species richness. Within cutting treatments, richness increased relatively more in the plots that were cut by a machine. Results from the 6-year field experiment suggest that mulching is the most cost-effective management regime in floodplain meadows, but only in combination with mowing (cutting with removal of the hay crop) every second or third year, providing the best management practice in the long run.