Coenopopulation vitality structure of Crassulaceae DC. species in the South Urals

The paper deals with results of vitality structure investigation in natural coenopopulations of Crassulaceae family 4 species: Hylotelephium triphyllum (L.) H. Ohba, Hylotelephium stepposum (Boriss.) Tzvel., Aizopsis hybridа (L.) Grub^ and Orostachys spinosa (L.) C.A. Mey in the South Urals in the Republic of Bashkortostan. These species belong to the leafy succulent group and grow in different ecological conditions: from river floodplains to dry rocky steppes. Vitality structure studying is important for understanding the stability mechanisms of Crassulaceae species in a broad ecological gradient. This analysis is highly informative because of its close interrelation with morphometric parameteres of plants. Investigations were carried out in 27 coenopopulations. Measuring of 25 middle-generative plants was conducted in every one. To characterize vitality by Yu. A. Zlobin method, a determined complex of key vegetative and generative sphere attributes was determined for every species using correlation and factor analysis. Depending on these attributes' meanings, all individuals were divided into vitality classes. Quality index of coenopopulation (Q-index) was determined based on proportion of plants individuals from different vitality classes. All coenopopulations were classified as thriving, equilibrium or depressive by Q-index meaning. According to the estimation of coenopopulation quality index 3 coenopopulations Hylotelephium triphillum, 1 coenopopulation Hylotelephium stepposum, 2 coenopopulations Aizopsis hybrida, 1 coenopopulation Orostachys spinosa were determined as thriving, 2 coenopopulations Hylotelephium stepposum, 1 coenopopulation Orostachys spinosa were detrmined as equilibrium, more than half of all coenopopulations were determined as depressive (7 coenopopulations Hylotelephium triphyllum, 3 coenopopulations Hylotelephium stepposum, 3 coenopopulations Aizopsis hybrida and 4 coenopopulations Orostachys spinosa). In consequence of vitality status estimation the most advantageous habitat characteristics could be suggested for species growing. For Hylotelephium triphillum, it is the slightly disturbed habitats with moderate humidity and presence of trees and a shrub layer in phytocoenosis. For Hylotelephium stepposum, moderate rocky soil is required in addition. Humidity plays a leading role in Aizopsis hybrida preferred habitats formation too, whereas for Orostachys spinosa the presence of strong competitors in phytocoenosis limiting its growth and development comes to the first place, as well as soil stoniness.

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