Analysis of the distribution and populations structure of Hedysarum grandiflorum Pall. (Fabaceae) in the southern part of the Volga Upland

For the first time in the southern part of the Volga Upland, a detailed study of the population distribution and structure of rare and protected species Hedysarum grandiflorum Pall., listed in the Red Books of the Russian Federation (2008) and the Saratov Region (2021), was carried out. The study was conducted in 2007–2021. To identify the distribution, data from routine observations and information from herbarium specimens, literary data and oral reports were used. The determination of the abundance and density was carried out in all encountered cenopopulations (CP), and for a detailed description of structure, 23 CP were studied with the laying of more than 600 discount areas and with a description of more than 3600 individuals of the average generative state of the sweetvetch. It was revealed that all CP in study area occupy a total area of about 30.8 ha, on which there are at least 2.068 million individuals of the sweetvetch, of which about 1.305 million are generative. The average density of individuals ranges from 4.6 to 18.4, and of generative from 2.8 to 11.4 ind./m2. From the northeast to the southwest of the southern part of the Volga Upland, the number of individuals and the density of CP of the sweetvetch decrease, and the areas of CP decrease. The basic ontogenetic spectrum of CP in the study area is unimodal, centred, with a maximum at the mature generative state, but due to small temporal shifts of the ontogenetic spectra to the left, the type of dynamics of the age composition is fluctuating. CP are, as a rule, normal complete, transitional and mature, with an average level of vitality and are in a stable state. A comparison is made with data from other regions. The results obtained can be used in organizing and maintaining SPNR, compiling floristic lists, introducing and reintroducing H. grandiflorum and similar species, and selecting initial material when introduced into culture.