Features of the ontogenetic structure of Helichrysum arenarium L. (Asteraceae) coenopopulations in the different phytocoenosis under the conditions of the Shostka district, Sumy region (Ukraine)

The paper contains the characteristics of Helichrysum arenarium L. plants of various ontogenic stages and their percentage in six cenopopulations. On the ground of obtained results, conclusions are made regarding considering the ontogenic structure of H. arenarium cenopopulations in the conditions of Shostka geobotanical district, Sumy region (Ukraine). Complex assessment of the ontogenic structure of populations using a specialized software and conventional methodologies, showed that the majority of populations are represented by plants of 4–8 ontogenic stages. Most constant are the generative and old individuals present in all investigated cenopopulations. Based on the ratio of the age index and the efficiency index (values of Δ / ω), it was determined that majority cenopopulations are ageing. The value of the age index (by the method of Kovalenko I. M. [9]) is bigger than 1 in all investigated cenopopulations, suggesting the prevalence of degradation processes. According to the classification of T. O. Rabotnov, all investigated populations belong to the category of “normal”. All main characteristics of populations indicate their potential for sustainable existence in the study region. However, their viability appears to be different, with the most evident imitations being faced by the populations under the pine forest canopy (populations are incomplete as to the presence of various ontogenetic states). In contrast the populations growing in Pineto (sylvestris)–Aceretum (platanoiditis) helichryosum (arenarium) and Helichrysetum (arenarium) phleosum (pratense), аs well as Achilletum (millefolium) helichryosum (arenarium) is community distinguished by the most complete ontogenic structure. As a result of radical changes in natural ecosystems, there is a decrease in the populations of many species, which prompts us to find directions and ways of regulating the mechanisms of development of natural phytocenoses. As a promising scientific direction, the application of the morphometric and vital analyzes to the investigated cenopopulations for evaluation of sustainability parameters of the H. arenarium individuals in the studied area.