Ontogenetic structure of Thymus baicalensis (Lamiaceae) coenopopulations in South Siberia

No information is available about the ontogenetic structure of T. baicalensis coenopopulations. The aim of this paper was to study the ontogenetic structure of T. baicalensis coenopopulations in the southern Siberia. In different regions of Tuva and Predbaikalye we studied 5 T. baicalensis coenopopulations. We used traditional methods (Uranov, 1975; Coenopopulations ..., 1976; Zaugolnova, 1994; Zhivotovsky, 2001). We found that under different environmental conditions (on hilltops and hill slopes of mountain steppes, on deflationary planes of sandy steppes) the studied coenopopulations were normal, mature and mainly incomplete. Their ontogenetic spectrum was central and coincided with the characteristic spectrum. The ontogenetic spectrum changing for the left-hand and bimodal spectrum types was temporary and due to the wave processes of their development. Ecological density of T. baicalensis coenopopulations depends on the substrate existence and nature. In mountain steppes, amid the large stone outcrop with a lack of the substrate, the ecological density of coenopopulations is the highest (more than 30 ind./m); on slopes in mountain steppes the parameter reduces sharply (up to 10 ind./m). In sandy steppes, the ecological density is rare (up to 3 ind./m). The similarity of the biological characteristics of T. baicalensis individuals in different habitats, types of coenopopulations and the ontogenetic spectrum with the characteristic spectrum indicates a stable condition of the studied coenopopulations in steppe communities in the southern Siberia.

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