Vegetation features and cenopopulation condition of Oxytropis spicata (Pall.) O. et B. Fedsch at the northern border of their occurrence (Sverdlovsk region)

In Sverdlovsk region there are several endemic and relict plant species that are at the border of their occurrence, often in isolation from the main area, constituting the most vulnerable part of the local flora. Oxytropis spicata (Pall.) O. et B. Fedsch. Is a mountain-steppe endemic of the South Urals that scarcely spreads in the Middle Urals. The basic part of the species area is located in the Bashkortostan Republic and Chelyabinsk region (See Figure 1). In Sverdlovsk region the species reaches the north border of its range and is only localized at 5 points now. As a vulnerable species, it is included in the regional Red Book. Special investigations of Oxytropis spicata population condition have never been conducted earlier. The aim of the research was to study the ontogenetic structure and to reveal the laws of changes in individual morphometric features in O. spicata marginal populations in the Urals. We studied three localities (cenopopulations) of the species in Sverdlovsk region, two of them are hills situated in the forest-steppe zone: "Bol'shaya" (56°43'N, 57°47'E) and "Ostren'kaya" (56°43'N, 57°47'E), and one is a bank slope in the subzone of south taiga "Rezhevskaya" (57°25'N, 61°29'E). In each locality, we identified the species coenotic confinement and studied the largest of available cenopopulations. The basic ecotopic and phytocenotic parameters are shown in Table 1. The age structure of all studied cenopopulations is normally distributed. In the ontogenetic spectrum of the cenopopulation "Ostren'kaya" all ontogenetic groups are present. The cenopopulations "Bol'shaya" and "Rezhevskaya" have no post-generative individuals. We revealed that to the north border of O. spicata occurence the humidification of its habitats increases. In the most northern habitats O.spicata changes its confinement to steppe cenosis and occurs under the canopy of steppificated pine forests with thinned grass cover. The analysis of morphometric features variability demonstrates that all the features in the populations, except numbers of generative and vegetative shoots, are characterized by low and medium variation rate (CV < 20%). Also, we established the relation of both individual and population indices with geographic position (See Table 2). The most northern cenopopulation has significantly fewer flowers in an inflorescence, as well as generative and vegetative shoots. The two southern cenopopulations are indistinguishable by the number of generative shoots and flowers in an inflorescence, but are dissimilar significantly to the northern cenopopulation. The species cenopopulation in the boreal zone are dissimilar to cenopopulations in the forest-steppe zone by low values of its basic demographic parameters, i.e. abundance, density, vitality and viability indices, and also by contagious distribution of its individuals in a plant community (See Table 3, Figure 2). The highest population indicators are attributed to the cenopopulation "Ostren'kaya" which is located under ecological-coenotic conditions close to those found in the Central part of the species area. The article contains 2 Figures, 3 Tables, 39 References.

Keywords

Authors

References