Soyanskiy regional-level biological nature reserve is located in the north of the Arkhangelsk Region mainland, in the center of the White Sea - Kuloy Plateau. The plateau is made up of sedimentary rocks: limestones, dolomites and marls of the Carboniferous and Permian geological periods. The most typical karst landscape feature in the reserve is karst-glacial valleys. In 2011, the study of the vegetation of these valleys was initiated and the diversity of treeless communities and the composition of their partial floras were identified. The partial flora composition of karst heaths and grasslands was studied based on 31 geobotanical relevés from karst-glacial valleys. The plant communities were classified into four types: heaths, dry meadows, low grasslands and high meadows. In total, 139 species of vascular plants of 98 genera and 32 families were identified in the meadows, grasslands and heaths. Boreal species prevailed in the partial flora of the studied treeless communities. The proportion of species of more northern (arcto-alpine, hypoarctic, hypoarctic-alpine) and more southern (boreal-nemoral, nemoral, forest-steppe) latitudinal groups was low. Seven species (Dracocephalum ruyschiana, Epipactis atrorubens, Gentiana verna, Koeleria grandis, Paeonia anomala, Pulsatilla patens, Salix arbuscula) are rare for the Arkhangelsk Region.