The aim of the study was to determine the distribution of prevailing forest types within the catchment areas of the biggest rivers in the north-east of Ukraine. During the allocation of the catchment areas of the studied rivers, the MapInfo Professional 12.5 program and the vector map of Ukraine were used. The research covered the forest area (more than 502,000 ha) of the state forest enterprises managed by the State Forest Resources Agency of Ukraine. The studied area located on the tributaries of the Sula, Psel, Vorskla and Siversky Donets rivers within the Poltava, Kharkiv, Sumy, Chernihiv, Kyiv and Cherkasy administrative regions of Ukraine. The analysis of the forest fund was carried out based on the electronic subcompartment database of the Ukrderzhlisproekt Production Association, using the application software and geoinformation technologies. It was revealed that a large variety of forest types in the tributaries of the Sula, Psel, Vorskla and Siversky Donets rivers as well as the prevalence of fresh fertile maple-lime oak and fresh fairly infertile oak-pine forest types (in 75 tributaries of Psel, Vorskla and Siversky Donets rivers) and fresh fertile maple-lime oak and fresh fertile hornbeam oak forest types (in 20 tributaries of the Sula River) are due to the relief, hydrological and soil-climatic conditions of the studied area, as well as anthropogenic factor. Assuming homogeneous natural conditions, an insignificant number of forest types are formed (up to five). For a large variety of natural conditions, there are at least six forest types that should be taken into account during forest management, along with the characteristics of the catchment areas of tributaries. The analysed data on the total number of forest types in the catchments of rivers would be appropriate to use in the future when creating a single list of forest types for the Left-Bank Forest-Steppe zone of Ukraine. The prevalence of certain forest types within the catchment areas of tributaries of the Sula, Psel, Vorskla and Siversky Donets rivers directly depends on the soil and climatic conditions, geomorphological structure, relief and anthropogenic influence in the forests. The results should be used in forest management activities to preserve and restore the species diversity of forests within the river catchments.
The literature review article sums up research experiences in natural seed regeneration in oak forests. In the past, the natural habitat for pedunculate oak (Quercus robur L.) was considerably wider than now. The downward trend in the area of oak stands is observed both in Ukraine and other European countries. In Ukraine, the area of natural oak stands of seed origin is decreasing by 2.0 thousand hectares each year. The most significant environmental factor in the emergence and normal growth of young oaks of seed origin is the light amount, which should reach at least 20% of the full sunlight. In addition to the light, the main factors contributing to the emergence of oak seedlings under forest canopies and in cutting areas are the oak fruiting and the litter and soil moisture. On the contrary, the excessive development of forest live cover with sedge and cereal vegetation, root competition from the parent trees, and a dense undergrowth were the hindering factors. In the forests of Ukraine, the largest number of natural seed reproduction of oak (more than 100 thousand stems ha−1) after the harvest year was recorded under the canopy of mature and overmature oak forests with a stocking of 0.6–0.7 and with 70 oaks in the stand species composition, growing in conditions of fresh and moist oak forests of Polissya and Forest-Steppe zones. Scientific and methodical guidelines for using natural reproduction of valuable species during the natural seed regeneration of oak stands were improved.
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”.