Vegetation of feather grass steppes in the western Pamir Alai Mountains (Tajikistan, Middle Asia)
Nowak, Arkadiusz; Nowak, Sylwia; Nobis, Agnieszka; Nobis, Marcin
Aims: To propose the first syntaxonomical scheme for the graminoid steppe vegetation of the montane and alpine zones in the Pamir-Alai Mts. in Tajikistan with some remarks on its environmental gradients. Location: Tajikistan. Methods: A total of 155 relevés were sampled in 2015 using the seven-degree cover-abundance scale of Braun-Blanquet and subsequently 148 of these relevés were selected and classified by the modified TWINSPAN method using the four step interval scale with cutoff levels of 0%, 5%, 10% and 25% and total inertia as a measure of cluster heterogeneity. Diagnostic species were identified using the phi coefficient as a fidelity measure. The detrended correspondance analysis was used to determine the relation between steppe, scree and rock plots and the major gradients in species composition. Results: Four associations – Stipetum drobovii, Stipetum lipskyi, Stipetum margellanicae and Stipetum jagnobicae – were distinguished, as well as two communities of Bromus tectorum-Stipa arabica comm. and Stipa turkestanica subsp. trichoides comm. Because of their floristic distinctiveness, all of these communities were assigned to the new alliance Poo bulbosae-Artemision persicae and the provisionary order Carici stenophylloidis-Stipetalia arabicae. The identified plant communities were included temporarily in the Irano-Turanian class of steppe vegetation – Astragalo microcephali-Brometea tomentelli Quézel 1973 em. Parolly 2004. The main factors determining the species composition of the studied associations are altitude and cover of organic top soil, which have a major influence on the development of the particular type of steppe vegetation. Conclusions: For the first time, we have initiated research on the diversity of steppe vegetation in Tajikistan and Middle Asia. The final assignment of the western Pamir Alai graminoid steppe phytocoenoses, particularly at the higher syntaxnomical rank with identification of relations between the Cleistogenetea squarrosae and the Astragalo-Brometea steppes, needs further detailed investigation in the surrounding areas of Middle and Central Asia.