Vegetation of hot semi-deserts, badlands and related ruderal vegetation in western Tajikistan (Middle Asia)

Aims: To complete the syntaxonomic conspectus of the vegetation of Tajikistan, hot semi-deserts and ruderal vegetation, mainly of the lowlands and montane belt, were surveyed with some remarks on their environmental predictors. Location: Tajikistan.

Methods: A total of 143 relevés were sampled in 2022 using the seven degree cover-abundance scale of Braun-Blanquet. All these samples were classified by unsupervised k-means analysis with cut-offs of 0%, 5%, 25% and Hellinger transformation. Diagnostic species were identified using the phi coefficient as a measure of fidelity. Non-metric multidimentional scaling analysis was used to show the relationship between groups in the dataset with passively plotted environmental variables, to identify the influence of key environmental factors.

Results: Four new associations - Artemisio annuae-Dittrichietum graveolens, Eminio albertii-Haloxyletum persici, Leptalaeo filifolii-Calligonetum grisei and Clematidi songaricae-Ephedretum intermediae were coined. In addition, two vegetation types already known from Eastern Europe were found: Sagino procumbentis-Bryetum argentei and Amarantho blitoidis-Tribuletum terrestris. Three plant communities were additionally identified: Alhagi kirghizorum-Chrozophora tinctoria, Halimocnemis hispida-Microcephala lamellata and Salsola montana-Halogeton glomeratus. A new alliance (Carici physodes-Haloxylion persici) was proposed for the hot semi-desert shrublands of the Irano-Turanian region, and for the vegetation of large rocky outcrops, screes and badlands in the subhumid zone of Pamir-Alai, the alliance of Ephedro intermediae-Spiraeion baldschuanicae was proposed. The main factors responsible for the species composition of the studied vegetation are altitude, mean annual temperature and annual precipitation.

Conclusions: The dryland and ruderal vegetation of Tajikistan as in the whole arid Middle Asia is species rich and diverse, and deserves further detailed studies. Our research provides a first insight into this anthropogenic and natural vegetation of lowland, warm and often deserted areas, which are undergoing strong changes due to climate warming, grazing and urbanisation.