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.
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.