Population-based studies of endangered plant species are key methods for assessment of the status for these plants at any territory. Plant species of the Orchidaceae family are sensitive components in natural ecosystems. That is why determination of the status for their populations can be considered as indicators for the status of natural ecosystem position as a whole. Investigations of three Orchidaceae species populations (Orchis militaris L., Epipactis palustris (L.) Crantz, Malaxis monophyllos (L.) Swartz) were carried out in Central Russia (Republic of Mordovia). Abundance, density, structure and dynamics of populations of these species were studied. Species composition of accompanying flora was established for each rare species. Some morphometrical parameters of individuals for the studied species were measured. Features of ontogenetic spectrum for Orchis militaris and Epipactis palustris populations were shown.
There are 15 plant species included in the Russian Red Book, which occur in the Republic of Mordovia: Najas tenuissima, Koeleria sclerophylla, Stipa dasyphylla, S. pennata, S. pulcherrima, S. zalesskii, Fritillaria ruthenica, Iris aphylla, Cypripedium calceolus, Cephalanthera rubra, Epipogium aphyllum, Neottianthe cucullata, Orchis militaris, Neotinea ustulata, Thymus cimicinus. Of these, only C. calceolus is included in the Global Red List as Critically Endangered. Threat status for studied species in Mordovia was assessed, and their distribution dynamics in this region throughout 12 years was described. Recent floristic studies, inspections of herbariums and literature were used for searches all provided data. Grid mapping and IUCN criteria were used. Nine taxa were determined as Critically Endangered, three as Endangered, one as Vulnerable, one as Near Threatened and one as Data Deficient. The areas of occupancy and extent of occurrence in Mordovia were assessed for each taxon. All studied species should be included in the next edition of the Mordovian Red Book. F. ruthenica, E. aphyllum, N. ustulata, T. cimicinus require additional studies to confirm earlier observations.