| Summary: | Seslerio uliginosae-Scorzoneretum purpureae is the only xerothermic community of the Festuco-Brometea class, where a rare species known as Sesleria uliginosa occurs in Poland. A couple of sites hosting this association in the Nida Basin were described in the 1920s and 1950s. All these stands are now situated in the areas designated as xerothermic nature reserves. The study aimed at describing the present-day characteristics of this rare association, the most likely being endemic in Poland, as well as the changes that have occurred in it. The species diversity and the contribution of xerothermic plants have decreased significantly in terms of their number and cover coefficient. Some of the diagnostic species of the association have become extremely rare. Sesleria uliginosa is the only one without visible changes in their dominant position in the community. Mosses, that have played a significant role before, were among the vanished species. At the same time, an increase in number and cover of mesophilous meadows species was observed. Mesophilous grasses belong to the group of species growing in significance in the phytocoenoses. The observed changes in species composition were reflected in a statistically significant increase of nitrogen indicator value. The slow process of succession observed in the Seslerio-Scorzoneretum purpureae could be attributed to the lack of appropriate land use, e.g. mowing and grazing that have been ceased in the nature reserves.
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