Calciphilous communities with Thymus dubjanskyi Klokov et Des.-Shost. in the Samara region

Rare plant communities with the participation of Thymus dubjansky, an endemic of the Middle Volga region, were studied on the chalk slopes in the Samara region. Using the approach of J. Braun-Blanquet, a total of 30 relevés were processed with the JUICE software. The primary classification by the TWINSPAN algorithm revealed two distinctive communities. The DCA ordination was performed, and reliable correlations were found between the position of the phytocenoses and L.G. Ramensky’s environmental indicators. The identified communities differed in terms of their environmental indicators and exhibited floristic heterogeneity. They were represented by typical steppe taxa and calciphilous species, 30 % of which were rare. For the first time, two new associations were established in the сalciphilous vegetation of the Samara Pre-Volga region: Artemisio salsoloidis-Thymetum dubjanskyi ass. nov. hoc loco and Gypsophilо volgensis-Thymetum dubjanskyi ass. nov. hoc loco. Due to their narrow distribution range, the communities with Thymus dubjansky were classified only provisionally. The сalciphilous subshrub communities of the established associations correspond to the initial stages of overgrowth on the slopes and elevations of chalk massifs in the Samara region. Given the vulnerability of their substrate to natural and anthropogenic degradation, the phytocenoses with Thymus dubjansky should be considered rare.