Vegetation of taluses and screes of the high montane and alpine zone in the Pamir Alai Mountains (Tajikistan, Middle Asia)

This paper presents the results of phytosociological research on scree vegetation of the Pamir Alai Mts. In total, 128 phytosociological releves were made during field studies conducted in 2012-2014, applying the Braun-Blanquet method. Plant communities of mobile and fairly stabilised scree of colluvial cones, aprons and fans, inhabiting mainly the high montane and alpine zone in several ranges (e.g. the Zeravshan, Hissar, Hazratishoh, Darvaz, Rushan and Vanch Mts) are herein described. A hierarchical syntaxonomic synopsis of scree communities at montane and alpine elevations in the Pamir Alai Mts is provided. The collected vegetation samples represent the majority of the variations among the phytocoenoses of gravel, pebble, cobble and rock block slides and scree in the high montane and alpine zones. As a result of field studies and numerical analyses, nine associations - Anaphallidetum zeravschanicae, Angelicetum ternatae, Feruletum foetidissimae, Feruletum koso-poljanskyi, Feruletum sumbuli, Feruletum tenuisectae, Hedysaretum flavescentis, Stellarietum turkestanicae, and Tetrataenietum olgae - have been distinguished, as well as one subassociation, Feruletum foetidissimae mediasietosum macrophyllae. Because of their floristic distinctiveness, all of these communities have been assigned to a new alliance (Ferulo foetidissimae-Vicion kokanicae) and a provisional order (Sileno brahuicae-Scutellarietalia intermediae) within the central Asian class of scree vegetation Artemisio santolinifoliae-Berber-idetea sibiricae. The main factors determining species composition of the studied associations are the scree mobility, rock particle size, elevation above sea level and slope inclination. Rupicolous habitats in Tajikistan, probably because of their high degree of separateness and marginal position within the Irano-Turanian province, act as a refuge for many narrowly distributed plant taxa and present remarkable variability in terms of species composition and habitat requirements. A synopsis of the scree plant communities of the Pamir Alai is proposed.