Morphological variations of Thymus in the vegetation belts of the Tien Shan mountains (Central Asia)

Abstract

This study demonstrated the correlation between Thymus life-forms and conditions in the Tien Shan mountains, in which different vegetation belts can be located at different altitudes depending on a particular ridge. We selected four species of Thymus that are widespread in Tien Shan mountains (Thymus diminutus Klokov, Thymus dmitrievae Gamajun, Thymus karatavicus Dmitrieva, and Thymus seravschanicus Klokov). Eco-morphological and phytocenotic approaches were used to study the life-forms and biomorphs within the genus Thymus in this region. The module structure and sympodial axis were analyzed according to the slope steepness and stone and (or) herbaceous covering. Acrotonic and basitonic module branching types are characteristics of dwarf shrub and dwarf subshrub life-forms, respectively. The dwarf shrub develops in open spaces in the steppe and forest, and the dwarf subshrub develops in different vegetation belts from steppe to alpine. Thymus dwarf shrub and dwarf subshrub life-forms were characterized by an implicitly polycentric biomorph type (mature plant comprising several closely located growth centers). Thymus species in the Tien Shan mountains exhibited morphological variability. We propose that the branching of Thymus plants can be used as an indicator of a specific vegetation belt in the Tien Shan mountains, and can be used to predict the behavior of other species with similar morphology.