Population status of Bupleurum aureum (Apiaceae), a Critically Endangered plant species in a region of European Russia

Abstract

Protected Areas are considered as an important and widely applied tool for biodiversity conservation. They are especially relevant for conservation of threatened species populations. This paper presents study aimed to investigate population status and suitability of habitat conditions of a regionally Critically Endangered plant species, Bupleurum aureum (Apiaceae). Our research has been conducted in National Park “Smolny” (European Russia). The field studies were carried out in 2008, 2013–2018 in two study sites (Plot1, Plot2). In each study sites, square plots (1×1 m) were established to cover the most number of B. aureum individuals. The population status was assessed on the basis of the morphometric traits of individuals (height of generative individuals, number of umbellulas per umbella, number of schizocarpiums per umbellula), number of individuals per population, age structure of populations, composition of accompanying flora. We analysed relationships between environmental conditions (shadiness, soil moisture, salt regime of soil, soil nitrogen, soil pH, soil moisture variability) and morphometric and population traits of B. aureum to reveal the most influencing environmental factors. We found that at the north-western limit of the range, B. aureum has relatively low abundance and height of individuals in compare to available data from other parts of its range. The population age structure indicated higher habitat suitability in Plot1 due to presence of both vegetative and generative individuals. At the same time, in Plot2, B. aureum population is under serious threat due to a lack of vegetative individuals noted during almost whole study period. We suppose a forthcoming threat of probable loss of this B. aureum population. Environment data obtained in both habitats of B. aureum populations in National Park “Smolny” (Russia) indicated high relationships between soil moisture and the number of inflorescences formed by plants. We suppose a threat of extinction of the B. aureum population due to the building activity of Castor fiber inhabiting the small river Bakhmustika located nearby of study area. If the small river will be dammed, it could lead to decrease in B. aureum population in both studied sites due to the increase in ground water level.