Structure and ecological features of the Yeravninsky steppes flora (Western Transbaikalia)

The paper is devoted to the characteristics of the floristic diversity of steppe vegetation in the southern part of the Vitim plateau in Yeravninskaya and Uldurginskaya basins. There is a southern border of the permafrost. The flora of the steppes is characterized by a depleted composition in comparison with the steppes of the Selenga middle mountains. Some widespread plant species of the true steppes of the Central Asia are absent here. The basis of the ecological and phytocoenotic structure is the steppe group, which is dominated by mountain and forest-steppe plant species. There is less participation of the true steppe species; this fact indicates an insular nature of these steppes. A group of light-coniferous species is significant; they are the part of the cryoarid forest-steppe complexes of the Vitim plateau. In the ecological structure of the flora xeromesophyte and gemixerophyte species dominate. They have the most important coenotic role in the formation of the vegetation cover of these steppes. The cereals species are of high coenotic significance, there are indicators of the dry bunchgrass steppes of Southern Siberia (Poa botryoides (Trin. ex Griseb.) Roshev., Agropyron cristatum (L.) Gaertn., Koeleria cristata (L.) Pers.). The role of mesoxerophytic of East Asian and Daurian-Manchurian species is also high (Filifolium sibiricum (L.) Kitam., Stellera chamaejasme L., Bupleurum scorzonerifolium Willd.). They are typical for meadow steppes of the Central Asian sector of the Palearctic.