Diversity, Distribution, and Classification of Chasmophytic Vegetation in the Central Asian Biodiversity Hotspot: Alpine Belt of the Eastern Pamir-Alai and Western Tian Shan Mountains

This paper presents the results of research conducted on chasmophytic vegetation occurring within the alpine belt (approx. 1,850-4,000 m a.s.l.) in the eastern part of Middle Asia. We specifically focused on the diversity and syntaxonomy of rock vegetation as well as on environmental variables determining its distribution. Altogether, 242 releves were sampled in rock fissures, ledges, and clefts during field surveys conducted in 2013-2019. The size of each recorded vegetation plot was 1 m(2). Five main groups of chasmophytic vegetation were distinguished in the studied area. Each group was confined to a specific combination of substrate type and climatic conditions. Altogether, 16 specific plant communities representing chasmophytic vegetation were defined in the study area. For each community diagnostic, constant and dominant species as well as its taxonomic composition and habitat characteristics are given. Seven communities were described: community of Androsace villosa var. dasyphylla, and associations of Crepidifolio tenuifolii-Stipetum tianschanicae, Parryetum schugnanae, Corydalideto bucharicae-Hippolytietum schugnanicae, Drabetum darvasicae, Acantholimonetum alexeenkoani, and Inuletum schmalhausenii are newly coined. Due to the extremely high endemism of the chasmophytic flora of the eastern part of Middle Asia, it is difficult to find strong relationships between the rock vegetation recorded in the region and that occurring in neighboring areas.