Vegetation of rock clefts and ledges in the Pamir Alai Mts, Tajikistan (Middle Asia)

Abstract

The paper presents the results of phytosociological research conducted on the vegetation of rock clefts and ledges in the Pamir-Alai Mountains (Tajikistan, Middle Asia). During the field studies, done in 2010-2012, 101 phytosociological relevés were taken. Plant species were recorded according to the Braun-Blanquet cover-abundance scale. Communities of calcareous rock clefts and ledges with small soil amounts from several ranges (Zeravshan Mts, Hissar Mts, Hazratishokh Mts, Darvaz Mts, Rushan Mts and Vanch Mts), inhabiting mainly the alpine and subnival zone, have been described. A synopsis of the rock communities of the Pamir-Alai is proposed. In the examined vegetation plots 77 vascular plant and 6 moss species were noted. The most frequent were: Achoriphragma pinnatifidum, Artemisia rutifolia, Asperula albiflora, Campanula incanescens, C. lehmanniana, Parietaria judaica, Pentanema albertoregelia, Poa relaxa and Stipa zeravshanica among vascular plants and Brachythecium albicans and Bryum caespiticum among mosses. Most of them are narrow endemics of Tajikistan or Middle Asia. The collected material presents most of the variability among the phytocoenoses of large crevices and rock ledges in limestone massifs in the alpine and subnival zones. As a result of field research and numerical analyses, 7 associations have been distinguished: Achoriphragmetum pinnatifidi, Asperulo albiflorae-Stipetum zeravshanicae, Inuletum glaucae, Paraquilegietum anemonoidis, Pentanemetum albertoregeliae, Rhinactinidietum popovii and Saussureaetum ovatae. The distinctiveness of habitat and species composition of Middle Asiatic rock communities makes it necessary to distinguish a new suballiance, Pentanemenion albertoregeliae, within the Asperulo albiflorae-Poion relaxae alliance. The main factors determining the species composition of classified associations seem to be the elevation above sea level and exposition. Alpine rock communities are one of the most unique and interesting plant formations in the moutainous areas of Pamir-Alai. Despite not being species-rich they often harbour many specialists adapted to harsh and extreme environments, especially in areas of Mediterranean-like climate