Pseudosteppes and related grassland vegetation in the Pamir-Alai and western Tian Shan Mts – the borderland of the Irano-Turanian and Euro-Siberian regions

The aim of our study was to complete the syntaxonomical scheme for grassland vegetation of the lowland, montane and alpine zones in the Pamir-Alai and western Tian Shan Mts in Tajikistan and Kyrgyzstan with some remarks on its environmental predictors. A total of 198 relevés were sampled in 2013–2018 using the seven-degree cover-abundance scale of the Braun-Blanquet approach. They were classified with k-means algorithm with tranforming cover values to three level scale of the following intervals 0%, 5% and 25% and total inertia as a measure of cluster heterogeneity. Diagnostic species were identified using the phi coefficient as a fidelity measure. Non-metric Multidimensional Scaling (NMDS) was used to explore the relationships between the distinguished groups. A total of 7 pseudosteppe, three typical steppe and three meadow communities were distinguished in the study area, grouped in four orders. Seven of them are established as new associations: Brayo pamiricae-Stipetum glareosae, Eremuretum bucharici, Hordeo bulbosi-Astragaletum retamocarpi, Potentillo orientalis-Eremuretum fusci, Achnathero caraganae-Delphinietum semibarbati, Eremuro tianschanici-Delphinietum biternati and Cryptosporo falcatae-Brachypodietum distachyi. The pseudosteppes were included in a new alliance – the Vulpio persicae-Caricion pachystylidis. The meadows have been divided into three communities: Ligularia alpigena-Euphorbia alatavica comm., Euphorbia lamprocarpa comm. and Carum carvi-Hordeum turkestanicum comm. The main factors differentiating the species composition of the researched vegetation are altitude, share of annual vs. perennial species, proportion of Euro-Siberian to Irano-Turanian plants and latitudinal position. We have completed the vegetation survey of the dry and mesic grasslands in the middle and western part of Middle Asia and have fostered the progress in finding the borderland between the boreo-temperate and mediterranean-like (Irano-Turanian) grasslands of the western Asian and central Asian subregions of the Irano-Turanian region.