Ontogenetic structure features of natural coenotic populations of Medicago cancellata Bieb. (Fabaceae) in the Samara Zavolzhie

The paper deals with natural populations ontogenetic structure features of Medicago cancellata Bieb. (Fabaceae). It is considered to be a rare representative of Samara flora. The rarity of the species determines the legitimacy of inclusion in the Red Books of the Russian Federation and certain regions. In the Samara Region it is a vulnerable species with a small number of habitats. We studied ontogenetic structure features of the coenotic populations in the Samara Zavolzhie. A total of 33 coenotic populations were studied, population change tendencies and demographic structure features were revealed and a basic ontogenetic spectrum was obtained. It was found that most of the populations of M. cancellata include uneven-aged individuals, being full-term. The structure of species populations is affected by ecological and phytocoenotic conditions of the environment and anthropogenic load. Sprouts and other individuals in the early stages of ontogeny badly need favorable conditions for growth and development. The centered spectrum of populations is formed in conditions of moderate disturbances (grazing, recreation). In case of strong disturbances of communities with participation of a model species (overgrazing, steppe falcons) the maximum of the spectrum shifts to the right. Populations of the species in the Samara Region are very vulnerable, since its habitats are subject to significant anthropogenic press, even in specially protected natural areas.