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The article focuses on the original approaches to the division of woody plant populations into individual structural groups-cohorts: seedlings, plantlets, small undergrowth, medium undergrowth, large undergrowth, young and generative trees of the tree layer. It is shown that the peculiarities of the natural reforestation process are indicative of the six generalizing models. One of them (Isp-Usml-Tym) corresponds to the renewal, which begins with the formation of seedlings of forest-forming species under the forest canopy that gradually reach the level of forest stand and generative ontogenetic state, gaining the ability to form the next cycle of natural reforestation. The other five (І-Usml-Ty, І-Usml, І-Usm, І-Us, І) characterize the situation where natural reforestation is not cyclical due to the fact that individuals of young generation cease to develop and exist before their transition to a generative ontogenetic state. The expediency of application of the vitality analysis to evaluate cohorts is justified. The authors' approaches to the study of the dynamics of vitality structure of cohorts by the stages of natural reforestation are proposed. The vitality structure of Pinus sylvestris L. cohorts formed in different forest site conditions of Left-Bank Polissia of Ukraine and its change by the stages of natural reforestation are described in detail. It is proved that in various models of natural reforestation the vitality cohort structure acts as a separate and very dynamic characteristic. The change in the characteristic features of the vitality structure by the stages of natural reforestation in P. sylvestris is very diverse. Despite the fact that the P. sylvestris cohorts of different groups of associations vary significantly by vitality parameters, there are clearly defined patterns in change in values of the quality index and vitality Chapter «Biological sciences» structure on simple gradients of the major ecological-coenotic factors. The vitality parameters of P. sylvestris cohorts are a response to the influence of a number of ecological and coenotic factors inherent in a particular habitat. The dynamics of vitality structure is manifested in the wide-scale implementation of its spatial and temporal variability and flexibility. On the territory of the Left-Bank Polissia of Ukraine, Pinus sylvestris is mainly dominated by the models of incomplete natural reforestation.

According to the results of the field researches, the state of the natural complexes of the territory (about 140 hectares) within the Yampil administrative district of Sumy region is characterized, the expediency of creation of a landscape reserve of the local value "Govorunovsky" in the studied territory is determined. Based on the analysis of flora and vegetation, it has been established that most of the territory of the proposed reserve is occupied by peaty meadows dominated by Deschampsia caespitosa (L.) Beauv and a number of typical meadow and meadow-swamp species. They are also growing here Filipendula ulmaria (L.) Maxim., Lysimachia vulgaris L., Veratrum lobelianum Bernh., Cicuta virosa L., Alopecurus pratensis L., Festuca pratensis Huds., Juncus conglomeratus L., Carex hirta L., Ranunculus acris L., Achillea submillefolium Klok. et Krytzka, Epilobium palustre L., Geum urbanum L., Galium mollugo L., Stellaria graminea L., Potentilla anserina L., Humulus lupulus L. In the more dry areas which are strip-shaped along the northern boundary of the projected reserve and, accordingly, the pine forest, grassy groups formed with the dominance of Agrostis canina L. or Nardus stricta L. It is noted that quite active natural restoration of tree species, such as Pinus sylvestris L., Betula pendula Roth, Pyrus communis L., occurs throughout the area of the proposed reserve. It has been shown that the sozological value of the reserve lies in the presence of typical for the floodplains of small rivers of Polissya natural complexes, as well as the presence in the flora of the species of the Red Book of Ukraine ‒ Dactylorhiza fuchsii (Druce) Soo, a number of valuable medicinal plants (Valeriana exaltata J. C. Mikan, Sanquisorba officinalis L., Achillea submillefolium Klock. et Krytzka, Mentha arvensis L., Thymus marschallianus Willd., Potentilla erecta (L.) Raeusch. etc.).

A detailed study of the herb layer species of forest ecosystems that are anthropogenically affected makes it possible to predict the successive changes and model the development of plant communities in particular areas. The study results of grassland species populations contribute to the restoration and preservation of unique groups that are part of forest ecosystems. Our research deals with understanding the mechanisms of adaptations that exist at the population level of the organization against the background of forestry impacts. With the comprehensive population analysis approach, the critical point is to observe the consequences after the transformation of the living conditions of plants. The research aim is to establish features and regularities of structural changes in the population typical for beech forests in Low Saxony, Germany, in terms of forestry use. Our research is based on the classical geobotanical and population analysis methods. We used morphometric, vital, gradient analyses, and mathematical statistics methods to process field research materials. It is curtained that the vitality determining features for A. europeaum were W - complete plant phytomass, Wl - leaves phytomass, and A � total foliage surface area. It was found that a significant part of the early generative ontogenetic stage of the Asarum europaeum population is represented in the unmanaged forest. In contrast, in the young forest plots of 40 and 70 years old tree species, the central part is devoted to the middle-aged and old generative ontogenetic stages, 31,25% and 34,33%, respectively. The vitality structure analysis investigated that herb layer species' vitality is remarkably higher in unmanaged forest.

Trapa natans L. s. l. is a typical representative speciesof the ecological group of attached higher aquatic plants with floating leaves. It is included to The Red Book of Ukraine. Despite the presence of diverse information on the main features of the structure of the vegetative and generative organs of Trapa natans, its ecological properties, distribution and significance, population and growth characteristics of this species remain virtually unexplored. We evaluated 10 morphometric and five allometric parameters, which characterize the growth of Trapa natans and found out the influence of leading ecologicalcoenotic factors on them: the thickness of water, its transparency and the overall projective coverage of phytocoenosis. Four old lakes, which located in the flood plain of the Desna River are covered by our studying. Grouping represented in these lakes are significantly different by degree of their rarity, as well as by the specific gravity and role of T. natans plants in their composition. The association Nuphar lutea subpurum is one of the typical for the region and the most common, the other three (especially Nuphar lutea + Nymphaea candida variant with Trapa natans) are comparable rare. The results of the studies showed that the water column factor significantly affects the values of all 15 dynamic morpho-parameters. The transparency of water factor did not show a statistically significant effect on the values of two morpho-parameters, and the projective coverage -at the value of three. For most morpho parameters, the power of influence on them of water levels are in the range of 45-75%, transparency -25-60%, and projective coverage -20-60%. It is shown that the greatest values of dynamic morphological parameters belong to the coenopopulation from the group Trapa natans subpurum, and the smallest to Nuphar lutea subpurum. Trapa natans better growth in reservoirs with a water column about 145 cm and its transparency about 80 cm, no current and muddy bottom sediments. It is noted that the effective natural inhibitors which are regulating the growth of Trapa natans are the reduction of water levels in the water column and the occurrence of successional processes that are accompanied by an increase the number of species of Nymphaeaceae in phytocoenoses. Сумський національний аграрний університет вул. Г. Кондратьєва, 160, м. Суми, Україна, E-mail: skvig@ukr.net Незважаючи на наявність ґрунтовної інформації про основні ознаки будови вегетативних та генеративних органів Trapa natans L. s. l., його екологічні властивості, поширення та значення, цілком очевидно, що популяційні та ростові властивості цього виду залишаються недостатньо дослідженими. Нами було виконана оцінка десяти динамічних метричних та п'яти динамічних алометричних морфопараметрів, що характеризують ріст Trapa natans та з'ясовано вплив на них товщі води, її прозорості та загального проективного покриття фітоценозу. Вивченням було охоплено чотири старичні озера, розташовані в заплаві р. Десни. Угруповання, представлені у них, суттєво відрізняють...

Some historical aspects of the formation of population ecology and biology as a separate scientific field are highlighted. It is noted that at the present stage, an integrated approach of studying populations is increasingly used. The work provides information on the main components of complex population studies implemented at the scientific school of plant population ecology created at Sumy National Agrarian University by Prof. Yu.A. Zlobin. The main achievements of the representatives of this school are shown, and it is also noted that, on the basis of their scientific achievements, the number of studied objects is gradually expanding. An example of this is the use of integrated population analysis for the study of protected autochthonous dendrosozophytes of Ukrainian Polissia whose representative, in particular, is Oxycoccus palustris Pers. Using the example of this species, the basic aspects of the application of complex population analysis are described, including determining the size of the population field, population density, size and morphological characteristics of individuals that form the populations, as well as the ontogenetic, size, and vital structure of populations. Based on such studies, swamp and forest-swamp phytocenoses were differentiated according to the degree of favorableness for the existence and functioning of O. palustris populations. At the same time, populations that can be considered as objects of regulated procurement of plant materials of O. palustris were identified. The conditions of the oligotrophic swamp and the grouping of Sphagnetum (cuspidati) eriophorosum (vaginati) are proved to be the most favorable for the formation of Oxycoccus palustris coenopopulations with high population density, vitality, diversity of size structure and balanced structure Populations from this grouping can be considered as centers of regulated harvesting of plant products and plant materials of the investigated species. Compared to swamp, forest-swamp phytocoenoses were less favorable for the formation and existence of coenopopulations of O. palustris, although they also revealed coenopopulations with a complex of high population characteristics Based on the results of studies and elucidation of the characteristics of populations, the original coenopopulation principle of constructing phytocenocompositions from species of natural flora was also proposed and tested. Its essence is that in the selection of certain species in the composition of phytocenocompositions it is necessary to rely on the indicators of phytocenoses, in which its populations have signs of ability for stable and long-term existence in the composition of plant groups The determinants features in this complex are the area of the population field, population density and characteristics of the structure, especially ontogenetic and vitality. According to the first feature of these traits, it is necessary that the populations belong to the group of young, transient or maturing and not to be aging or old, and according to the second – to represent the category of prosperous.

Studies were conducted on the territories of the Left Bank Polissia, which aimed to assess the state and find out the peculiarities and patterns of natural seed regeneration of the leading forest-forming species of the Left Bank Polissia of Ukraine � Pinus sylvestris L., Quercus robur L., Acer platanoides L., Betula pendula Roth., Populus tremula L. as a mechanism for ensuring the preservation and functioning of forest phytocoenoses of this region. Phytocoenoses of 24 groups of associations representing forest communities typical for the region were covered by the study. The studies were carried out based on the original system of the division of woody plant populations into intrapopulation structural groups - cohorts. Considering the established facts regarding the prevalence of cohorts in the phytocoenoses of the Left Bank Polissia of Ukraine, a special method of building phytocoenotic pyramids of natural restoration was developed. According to the results of the analysis of the condition and signs of phytocenotic pyramids, it is shown that the natural regeneration of each of the forest-forming species within the areas of the Left Bank Polissia of Ukraine has its own specific features signs of formation, distribution of cohorts and their transition from tier to tier of forest phytocoenoses. Although all these species are characterized by a tendency to decrease the prevalence of cohorts in the range small undergrowth > medium > large.

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