Abstract
This paper presents the results of phytosociological research on scree vegetation of the Pamir and south-western Tian Shan. We collected 222 phytosociological relevés during field studies conducted in 2015–2019, applying the Braun-Blanquet approach. We identified 21 plant communities on mobile and stabilized screes of colluvial cones, aprons and fans, inhabiting mainly the montane and alpine belts in several ranges (e.g. Peter the First, Alichur, Shugnan, Shachdarian, Darvaz, Rushan, Vanch, Fergana, Kyrgyz and Terskey ranges). As a result we provide the first comprehensive hierarchical syntaxonomic synopsis of scree communities at montane and alpine elevations in the eastern Middle Asia. The collected vegetation relevés represent the majority of the variation among the phytocoenoses of gravel, pebble, cobble and rock block slides and screes in the montane and alpine belts. As a result of field studies and Twinspan analyses, nine associations were identified on screes of the Pamir and western Tian Shan. All these communities were assigned to the Sileno brahuicae-Lactucetalia orientalis Nowak et al. 2021. Additionally, within the nitrophilous compact gravel screes one subassociation of Corydalidetum kashgaricae trigonelletosum gontscharovii was distinguished. In the most arid zone two additional plant associations and one subassociation were identified in gravelly semi-deserts zone. The main factors determining the species composition of the studied associations are scree mobility, rock particle size, elevation above sea level and slope inclination. Our research revealed considerable diversity of scree habitats of montane and alpine belts what might be astonishing regarding harsh environment of this mountainous territory. However, a great number of lineages that evolved here and particularly rich species pool of this habitat in Middle Asia facilitate remarkable diversity among vegetation of taluses and screes. The distinctiveness of species composition is additionally enhanced by high degree of endemism of chasmophytic habitats in the eastern part of Middle Asia. Despite recent developments, the prominent chasmophytic vegetation of Middle Asia still needs thorough studies focused on its relationship to semi-desert, tall-forb and petrophytic communities of high mountains of the Pamir, Hindu-Kush, Kunlun and Central Tian Shan.
Highlights
The territory of Tajikistan encompasses a vast area of mountain ranges and highly elevated plateaus in the Pamir-Alai mountain system
Because of considerable phytogeographical differences between the Pamir-Alai and the Tian Shan Mts, the research aims at comparing the scree vegetation of both areas including Alai, Transalaian, Alichurian, Shachdarian, Shugnan, Sarikol, Yazgulem and Peter the First ranges in Pamir-Alai and
When analysing the possible class assignment of the particular associations, we considered mainly the Thlaspietea rotundifolii Br.-Bl. 1948, as a syntaxon comprising the alpine scree vegetation of Europe; the class Heldreichietea Parolly 1998, which is related to talus of the east Mediterranean region; the Lamio tomentosi-Chaerophylletea humilis Belonovskaya 2012 reported from screes in the Caucasus (Belonovskaya 2012) and Artemisio santolinifoliaeBerberidetea sibiricae, which has been proposed to include vegetation types of scree and rocky slopes of Central Asia (Ermakov et al 2006)
Summary
The territory of Tajikistan encompasses a vast area of mountain ranges and highly elevated plateaus in the Pamir-Alai mountain system ( called Hissaro-Alai). Located between the continental Asian deserts in the west and south, and the great mountain ranges of Tian Shan, Kunlun, Hindu-Kush and Karakorum in the north, east and south-east, having all vertical belts from hot to permafrost deserts, it offers an outstanding range of biotopes for plants and vegetation. This extraordinary complexity of climatic influences, phytogeographical divisions and diverse land geomorphology affect the floristic composition and richness of plant species of this country. Because of this considerable floristic richness, the mountains of Middle Asia have been recognized by Conservation International as one of the 35 so-called hotspots of biodiversity (Mittermeier et al 2005) and as one of the eleven most important focal points of scientific studies and conservation efforts (Giam et al 2010)
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