The ontogeny and the demographic structure of the coenopopulations of the species Oxytropis chakassiensis (Fabacaea) in the steppe communities of Khakhassia (Russian Federation)

The article presents the results of the analysis of the demographic structure of ten coenotic populations of Oxytropis chakassiensis in near-Yenissei steppes (Khakassia and Krasnoyarsk krai). Most part of studied species coenopopulations are not complete and definitive, normal, mature, have a bimodal developmental spectrum with peaks at g1 (v)- and g3-individuals. Changes in the structure of the ontogenetic spectrum (increasing the share of young plants) depend mainly on the environmental conditions and the degree of human disturbance of habitats: rocky slopes and decrease in pasture digression create more favorable conditions for the survival of juveniles. The ontogeny of O. chakassiensis (the rare species of near-Yenissei steppes) was studied and its life- form was described. Four periods and nine ontogenic stages were distinguished. The results of our study showed that O. chakassiensis is was a petrophyte steppe species with strict ecological and cenotic propensity to petrophytic steppe with the prevalence Koeleria cristata , Festuca valesiaca, Arctogeron gramineum, Hedysarum turczaninovii, Alyssum obovatum and Thymus minussinensis . Due to long generative period O. chakassiensis is successfully renewed and is stable during long periods of extreme conditions of petrophytic steppes with high pasture digression.