The ecological and coenotic features of plant communities containing Colchicum bulbocodium subsp. versicolor (Colchicaceae) in the Lower Volga region

The article presents a phytocoenotic description of 23 plant communities with Colchicum bulbocodium subsp. versicolor studied during the period of mass flowering in 2014–2018. It was found that, across the Lower Volga region, the studied communities with C. bulbocodium subsp. versicolor are mostly confined to the slopes of south- and east-facing arroyos and more seldom to the southern and northern hill slopes, plains, arroyo and liman bases, and floodmeadows. During the period of mass flowering, 207 vascular plants were detected in the studied communities. Every community description included 9 to 36 species. Biological diversity was assessed with the Shannon index and polydominance index; the degree of dominance was measured with the Simpson index. The species similarity of the communities was evaluated through pairwise comparison with the Jaccard coefficient. It was revealed that C. bulbocodium subsp. versicolor occurs in communities varying in diversity and species composition. The subspecies is not confined to specific phytocoenoses. It usually grows on rich and, more seldom, fairly rich and slightly saline soils. Their alluviality is more often weak rather than moderate. Watering usually corresponds to the dry steppe or semi-desert climate type, rarely to the middle steppe type, being moderately variable and in some cases highly variable. The impact of grazing is usually weak, but it is either moderate or strong in some communities. The communities with C. bulbocodium subsp. versicolor are dominated by hemicryptophytes: mostly tap-root, short-rhizome and long-rhizome herbaceous perennials. In phytocoenotic terms, most species belong to the zonal type of vegetation, namely steppe vegetation. The participation of meadow species is prominent. The share of weed species is rather high, which indicates a significant anthropogenic load on the studied communities.