Rare plants of the mykhailivs'ka tsilyna nature reserve.
The Mykhail ivs a tsilyna Nature Reserve is located in the Lebedinsky district of Sumy region on the riverside of the Grun and Sula rivers. In 1928, the Reserve received the status of a local important object of Nature Reserve Fund. In 1947, on its basis was created a Reserve of national importance " Mykhailivs'ka tsilyna ". From 1961 to 2009, this object was a part of the Ukrainian Steppe Reserve. In 2009 he regained his independence. Presently, the reserve has an area of 882.9 hectares, the share of absolute reserveterritori is 202.4 hectares. The reserve preserves a unique placor forbs-grasses step dominated by steppe turf grasses. A geobotanica l survey in 1956 showed that the reserve was dominated by phytoceonoses with turf grasses, in particular, Stipa capillata L ., Festuca valesiaca Schleich. ex Gaudin were dominance species. In small areas phytoceonoses dominated by Stipa pennata L. or Stipa tirsa Steven . These types of vegetation has unique natural value. There are noticeable transformations in the flora of the M y khail ivs'ka Tsilyna Nature Reserve . Some species of steppe plants disappear. There is quite a significant inclusion in the steppe p hytocenoses of the invasive plant species. There is a general mesophytization of the flora, manifested by the displacement of the steppe species and their replacement by meadow species of plants. R are plant species and their populations are an important b ioindicators of flora and phytocenoses . That is why our research has focused on their study. To estimate the ecological amplitudes and ecological optima of the rare plant species of the M y khail ivs ' ka Tsilyna Nature Reserve, we used ecological scales of Ya . P . Diduch. The overall resistance of a particular plant species to one or another group of environmental factors was assessed using the tolerance index. In general, Pulsatilla patens (L.) Mill, Bulbocodium versicolor (Ker Gawl.) K. Perss., Adonis vernalis L. and Stipa tirsa Steven . are the most sensitive to changes in environmental factors due to the narrow range of ecological niches within the territory of the M y khail ivs ' ka Tsilyna Nature Reserve . These types of plants may fall out of its flora first. In general, rare plants in their relation to climate - edaphic factors are form ing three groups: stenobionts, hemostenobionts, mesobionts. In the conditions of increasing mesophytization of the vegetat ion of the M y khail ivs ' ka Tsilyna Nature Reserve, three types of stenobiont plants may be in greatest danger. Bulbocodium versicolor, Adonis vernalis and Stipa tirsa are the most vulnerable in the hemistenobionts group.