Features of the composition and structure of communities with Acomastylis glacialis in the area border (Subpolar Urals)
Vegetation of the west macroslope in the highest part of Subpolar Urals that includes Barkova Mountain is understudied. Acomastylis glacialis is rare plant species in the Komi Republic of Russia living here at its border of distribution area. It was found in the rocky mountain belt of several peaks upstream the Kozhim River and the Schugor River. Vegetation of the Barkova Mountain was studied in 2012 and 2015. Rocky mountain deserts are mixed here with mountain tundra communities including herb-lichen ones where Acomastylis glacialis is relevant. 132 species (48 vascular plants, 25 mosses and 59 lichens) were revealed in the model community type Carex arctisibirica - Acomastylis glacialis - Alectoria ochroleuca located in the rocky mountain belt at the terrace on the top of the mountain and border slopes (1272-1321 m above sea level). Species richness is high (41-60 species). This is 1.5-2 times higher than in other bordering regions. Diagnostic species besides Acomastylis glacialis are presented by taxa with high (Carex arctisibirica, Poa arctica, Cladonia mitis, Rhytidium rugosum, Lagotis minor, Cladonia coccifera, Valeriana capitata, Solorina crocea, Rhodiola quadrifida, Myosotis asiatica, Bryoria nitidula, Salix numullaria, Stellariapeduncularis, Hylocomium splendens and Ptilidium ciliare) and average (Lusula nivalis, Polemonium boreale, Tephroseris atropurpurea, Politrichum juniperinum and Eritrichium villosum) abundance that occur rarely in the bordering regions. Total projective cover varied from 50 to 98%; vegetation plots are mixed with stones. Groups of Acomastylis glacialis are mixed with sites covered by lichens and Carex arctisibirica. Height of herbal plants is 15 cm, lichens - 5 cm. Specific feature of the studied communities is an occurrence of 21 vascular plant species protected in the Komi Republic. The data on composition and structure of communities Carex arctisibirica - Acomastylis glacialis - Alectoria ochroleuca add current information about mountain tundra vegetation of the Subpolar Urals are important for preservation these unique regional ecosystems. Classification of the community in the system of highest syntaxonomic units is still under discussion.