Classification of alpine grasslands in the western Tian Shan Mountains (Kyrgyzstan, Middle Asia)

Abstract

In this paper, we present the first syntaxonomic classification of alpine grasslands in the western Tian Shan Mountains (Kyrgyzstan) with some remarks on its environmental gradients. A total of 251 relevés were sampled in 2015-2022 using the seven-degree cover-abundance scale of the Braun-Blanquet approach. These were classified using the agglomerative hierarchical Ward’s method employing the Euclidean distance measure. Diagnostic species were identified using the phi coefficient as a fidelity measure. NMDS was used to explore the relationships between the distinguished groups. Our classification revealed 13 ecologically meaningful clusters corresponding to 12 associations and one rankless unit of alpine grasslands in Middle Asia. The new communities have been included in three new alliances: Aconito rotundifolii-Potentillion pamiroalaicae – subalpine and alpine mesic forb meadows and pastures in the western Tian Shan and shrubby subalpine chionophilous heaths of Middle Asia, Stipo regelianae-Ptilagrostion malyschevii – Kobresia mats and Artemision dracunculi – subalpine forb steppe vegetation. The main climatic factors differentiating the species composition of the researched vegetation are temperature seasonality, mean diurnal temperature range and a sum of annual precipitation. Among the soil factors the most important are pH, cation exchange capacity and nitrogen availability. Our study has expanded the knowledge of the alpine grasslands on the borderland between vegetation influenced by Irano-Turanian climate in Pamir-Alai and grassland vegetation of the alpine belt in Tian Shan. Their final classification certainly still requires further studies and comparisons, especially with the Alpine grasslands in the Altai region and some of the vegetation units closely related to Karakorum-Himalayan ranges.