Ecological-coenotic features of rare flora species of pine-oak stands of Volyn Polissya

Anthropogenic influence on the natural vegetation of Volyn Polissya threatens the existence of habitats of rare and endangered species of flora. Therefore, the region, unique in botanical and geographical terms, is gradually losing its specific vegetation characteristics. Having analyzed the literature data, herbarium data and materials of our own field studies in 2016-2019, we have compiled a list of rare and endangered species of pine-oak stands. In the habitat of pine-oak stands 89 rare species were found, 29 of which are listed in the Red Data Book of Ukraine, while Silene lithuanica is included in the European Red List. 3 species (Cypripedium calceolus, Trapa natans та Caldesia parnassifolia) are included into appendices of “The Convention on International Trade in Endangered Species of Wild Fauna and Flora”. 10 species are subject to protection according to the appendix of “Convention on the Conservation of European Wildlife and Natural Habitats” 56 species are regionally rare species for the flora of the Volyn region, 4 species are rare species of pine-oak stands. In our research we have analyzed the age range, density and recovery index for the species studied. The study found that for 63 rare species the dynamics of species abundance and distribution are satisfactory. The area of distribution and the number of 7 species is increasing: Allium ursinum, Galanthus nivalis, Platanthera chlorantha, Anemone sylvestris, Campanula persicifolia, Corydalis cava, Isopyrum thalictroides In the study area 14 species grow sporadically: Juniperus communis, Potentilla alba, Digitalis grandiflora, Gymnocarpium dryoptheris, Daphne mezereum, Neottia nidus-avis, Epipactis helleborine, Scorzonera purpurea, Asparagus officinalis, Iris sibirica, Adonis vernalis, Cephalanthera damasonium, Gentiana cruciate, Gentiana pneumonanthe. Dissemination information for Caldesia parnassifolia, Succisella inflexa, Genistella sagittalis, Salix myrtilloides, Ophioglossum vulgatum is insufficient for establishing species dynamics and needs further investigation. The conservation of pine-oak stands in Volyn Polissya will help to create the conditions for the growth of rare and endangered species of flora.


Introduction
Anthropogenic influence on the natural vegetation of Volyn Polissya threatens the existence of habitats of rare and endangered species of flora. Therefore, the region, unique in botanical and geographical terms, is gradually losing its specific vegetation characteristics. Information about the rare species of the flora of Volyn Polissya is given in the works of researchers, which mainly covered information about their geographical distribution (Vandas, 1986;Pachoski, 1900;Macko, 1937;Andrienko, et al., 2004Andrienko, et al., , 2009. The current status of rare flora species of pine-oak stands of Volyn Polissya has not been sufficiently investigated, there are no satisfactory data on the geographical location of the localities and the state of the populations of the species, there is no general analysis of the horological patterns. The purpose of the research is to establish ecological-coenotic features of rare flora species of pine-oak stands of Volyn Polissya.
To achieve this goal, the following objectives were set: -To compile a list of rare and endangered species of flora; -To conduct a sozological analysis of rare species; -To establish dynamic trends in the geographical distribution of rare flora species. Therefore, studying the features of the current distribution of rare flora species, monitoring their status and population structure is an urgent and important task, without which there are risks of the extinction of some rare species from the natural flora of the region.

Objectives and Research Methods
Field studies of rare and endangered species were conducted from 2016 to 2019. During this time, locations known for literary and herbarium data were checked and new rare species were found. Field surveys were carried out annually using forwarding methods in the territory of the Lopatyn, Ozersk, and Zviriv Nature Conservation Departments of Kivertsi National Natural Park "Tsumanska Pushcha". For each botanical permanent sampling area (BA) a passport was established, a geobotanical description was made, and the age spectrum of the population was analyzed. Phytocoenotic descriptions were performed by the method (Rabotnov, 1978). Population age structure and their types by age composition have been studied by methods (Uranov, 1975;Rabotnov, 1978). The analysis of 56 Ecological-coenotic features of rare flora species of pine-oak stands of Volyn Polissya Ukrainian Journal of Ecology, 10(1), 2020 the coenopopulations of rare species of flora was carried out on the basis of the quantitative ratio of plants of different ontogenetic states in permanent sampling areas. The study identified four age groups: juvenile (j), immature (im), virginal (v) and generative (g). For the analysis of the dynamics of self-sustaining population, the RI -renewal index was used as the ratio of the number of preregenerative specimens to the number of generative plants.

Results of the research
Information on the distribution of rare species of flora is given in the works of researchers of Volyn Polissya.
Having analyzed the literature, herbarium data and materials of our own field studies Shtokalo et al. 2017Shtokalo et al. , 2018, we have compiled a list of rare and endangered species of pine-oak stands. The list was based on the species listed in the "Red Data Book of Ukraine" and the dominant species of the "Green Data Book of Ukraine", in the Appendices of "The Convention on International Trade in Endangered Species of Wild Fauna and Flora", "Convention on the Conservation of European Wildlife and Natural Habitats" and other international rare plant lists, at "List of rare and endangered plant species in the Volyn region" (Table 1).  BA -17 -Ozersk NCRB SE "Kivertsi Forestry" Trostianets forestry, quarter 58. Population age range, density, and renewal index (RI) were analyzed for the species studied (Table 2).   Studies have found that the highest population density recorded was the following: Allium ursinum -4052 specimens/100 m 2 ; Anemone sylvestris -1606 specimens/100 m 2 ; Dentaria bulbifera -1289 specimens/100 m 2 ; Galanthus nivalis -1088 specimens/100 m 2 ; Dentaria glandulosa -606 specimens/100 m 2 . Populations of Orchidaceae have low quantity and density, rightsided spectra of ontogenetic states dominated by generative individuals: Cephalanthera damasonium -18-42 specimens/100 m 2 ; Epipactis helleborine -7-32 specimens/100 m 2 ; Dactilorhiza majalis -10-45 specimens/100 m 2 ; Dactilorhiza incarnata -6-8 specimens/100 m 2 ; Platanthera bifolia -26-35 specimens/100 m 2 . Population Betula obscura consist of 1 tree about 80 years old, seed reproduction is not observed. In January 2019, three trees were killed as a result of the storm.