Perennial vegetation is one of the most valuable ecological components when forming healthy living environments, natural and cultural landscape values, and general ecological stability, especially in protected areas. In various countries, increasing attention is being paid to research into biodiversity of meadow phytocenoses. Research in Western Lithuanian meadows was conducted from 2003 to 2006 with the aim to determine how the regime of management and different ecological conditions over several years influences floristic composition, frequency, and stability of meadow sward. Field sampling plots were set up on two semi-natural floodplain meadows in protected areas: in the meadow of the Minija mid-river banks (used for agricultural activities – grazing and cutting), and in the Veiviržas landscape reserve in the flood-meadow land (with no farming activities for the last ten years). The article discusses the relevance of the dominant species on the stability of phytocenoses. Each habitat was estimated for ecological conditions, i.e. soil moisture and vascular plant species indicating soil acidity.