Changes in the areas and stock volumes of oak stands were analyzed within the six administrative regions in the plain area of Ukraine, based on forest management data (subcompartment database) as of 2001 and 2016. The studied regions geographically related to the Left-bank Forest-Steppe zone of Ukraine (Kyiv, Poltava, Sumy, Kharkiv, Cherkasy and Chernihiv Regions). The analyzed area was over 284,000 hectares. The paper outlines the present state of the oak stands, concerning their origin (vegetative, natural seed and planted seed stands). Forestry-taxation indices of the stands were determined by grouping the plots according to age and further clustering in four age groups. The natural regeneration under a canopy in oak stands was accounted and estimated using circular 10 m2 (R = 178 cm) accounting plots. The oak forests were found to be dominated by stands of vegetative (coppice) origin (57%). Planted seed-origin oak stands covered 101,000 ha or 36% of the total area (284,000 ha). Stands of natural seed origin amounted to 7%. From 2001 to 2016, the total area of oak forests in the study region decreased by nearly 7,000 hectares. The analysis of literature sources allowed identifying numerous factors, which have the greatest influence on the emergence, liveability, and growth of natural regeneration of pedunculated oak. Only 20% of the investigated oak stands were found to have a sufficient amount of oak regeneration. For the implementation of sustainable forest management, activities should be aimed at optimizing the age structure of oak forests and growing natural forests from seeds.

The natural distribution area of common ash (Fraxinus excelsior L.) in the forests of Europe and Ukraine has been determined through the analysis of scientific works of Ukrainian and foreign researchers. According to the reference materials on the current state of Ukrainian forests (25 administrative regions), it is established that ash forests cover an area of about 150,000 ha or 2.4% of the total area of the country’s forests. Among them, common ash stands account for almost 87% or 130,000 ha; the rest are stands of introduced ash species, namely F. pennsylvanica Marsh., F. americana L., and F. lanceolata Borkh. The average age of ash stands is 59 years. Only 6.4% (8,300 ha) of the total area of ash forests is covered by pure ash stands, and the remaining area (93.6% or 121,700 ha) are mixed ones. It is revealed that the optimal natural and climatic conditions for the emergence, preservation and successful growth of natural regeneration of ash trees are fresh and moist fertile sites (rich in minerals) with well-drained soils, the light of at least 5–6% of that on an open space, and without abundant live ground cover. The highest number of seed regeneration of ash, about 7,000–8,000 stems ha−1 on average, was found under the canopy of mixed (ash share in the composition was 10 to 20% by stock) old (over 100 years old) stands with a relative density of stocking of 0.7–0.8. Promoting the natural seed regeneration of ash trees can be an effective way of increasing the sustainability of such stands and will ensure their preservation in the forests of Ukraine and in deciduous forests of Europe as a whole.

The study was conducted in pure Scots pine (Pinus sylvestris L.) forests and mixed forests of Scots pine and silver birch (Betula pendula Roth.) within the Chernihiv Polissya physiographic region of Ukraine. The aim of the study was a comparative analysis of forest mensuration characteristics and health condition of pine and mixed pine-birch stands planted on formerly arable lands and cutover areas after pine stands infected by annosum root rot. It was found that in pine stands planted on formerly arable land, the average diameter of living trees in the root rot disease focus was 1–6% larger and the average diameter of dead trees was 11–23% larger than those outside the disease focus. Due to the pathological loss inside the disease foci, the pine stand density was much lower – by 14–38% and the growing stock volume was 16–35% less as compared to the outside areas. Mixed pine-birch stands (with a predominance of pine trees), established on the cutover areas after pine stands affected by root rot, had a 20% greater stock volume and the birch-pine stands (with birch predominance) in the clear-cuts had 18% greater stock volume than pure pine stands inside the root rot disease area. The pine trees were assessed as “weakened” in the mixed stands and as “severely weakened” in the pure pine stand inside the disease focus. The birch trees in mixed stands were characterized as “healthy”.

Понятие леса, как единства насаждения, климата и почвогрунта, т.е. как экосистемы впервые было определено А.А. Крюденером. Ученый разработал классификацию лесов по плодородию почвогрунтов, на которых они произрастают, в координатах их обеспеченности элементами питания и влагой. А.А. Крюденер предложил первую экологическую классификацию лесов Европейской России по принципу районирования ее территории по основным климатическим показателям, с последующим разделением лесов в пределах климатических зон и областей на типы насаждений по особенностям петрографического состава и водного режима почвогрунтов. Определяющую роль в формировании типов насаждений внутри однородных в климатическом отношении территорий А.А. Крюденер, как и Г.Ф. Морозов, отводил почвенно-грунтовым условиям, подчеркивая при этом, что основополагающим фактором является не собственно почва как таковая, а почва как субстрат, как среда произрастания растений. Ученым, в процессе массового изучения почв разных типов леса, была выявлена тесная связь характера лесной растительности не с генетическими типами почв, а с их плодородием, с их лесорастительным потенциалом. При этом для оценки плодородия почв А.А. Крюденер использовал новый подход – метод фитоиндикации, то есть критерием качества почв им принята растительность, ее состав и производительность. Суммарным показателем плодородия среды является количество, соотношение и распределение по сезонам года лимитированных экологических ресурсов – тепла, влаги и пищи. Лесотипологические классификационные модели построены в координатах этих ресурсов – климатическая сетка в координатах тепла и атмосферного увлажнения, эдафическая – в координатах пищи и влаги почвогрунтов. Поэтому они применимы не только для классификации лесов, но и природы в целом. Охарактеризованы также основные достижения и вопросы сформировавшейся на этих принципах украинской экологической школы лесной типологии. Отмечены имеющиеся проблемы, требующие дальнейшего решения.

The aim of the study was to analyze the origin of oak stands within the catchments of the Vorskla’s tributaries and to describe their state. Covering 60,900 ha, pedunculate oak (Quercus robur L.) stands prevail and cover 51.1% of the total forest area of 119,200 ha in the catchment areas of the River Vorskla’s tributaries. The way oak stands are distributed in regards to trophotopes points at favourable conditions for their growth, as 81.7% of the area is a fresh fertile oak forest site type. Forest stands aged 41–80 years (39.8 % of the total area) and 81–120 years (50.4%) are prevailing. Natural oak stands cover almost 66.5% and planted ones grow at 33.5%. Distribution of oak stands in regards to the functional categories of forests shows a significant predominance of the protective forests. They cover 46.6% of the total area. The commercial forests cover 23.0%, the recreational ones make 18.8% and the forests with conservational, academic, historical and cultural purpose cover 11.6 %. Distribution patterns of oak forests in the catchments of the River Vorskla’s tributaries should be considered in the forest management in order to conserve their biodiversity and enhancing the performance of important environmental, protective, recreational and other functions. The article contains results of the study on the natural regeneration of Quercus robur and other wood species under the canopy of oak stands and on felling sites. The further research perspectives are a thorough study of the stand characteristics and the typological structure of forests in terms of certain wood species in the catchments of rivers all over Ukraine. It will help developing principles for the catchment and landscape zonation.