PATTERNS OF FORMATION AND ECOLOGICAL STRUCTURE OF THE SHRUB LAYER OF FOREST COMMUNITIES WITHIN THE VORSKLA RIVER BASIN OF POLTAVA REGION
DOI:
https://doi.org/10.32782/naturalspu/2026.1.8Keywords:
shrub layer, forest communities, adventive species, edifier, age dynamics, biological invasionsAbstract
The article investigates the patterns of formation, spatial, and ecological structure of the shrub layer in forest communities within the Vorskla River basin in the Poltava region. The relevance of the study is due to the fact that the shrub layer is an integral structural component of mature forests, which performs a number of important ecosystem services, creates a specific microclimate under the canopy, and directly affects the natural regeneration of tree species. The aim of the work is to establish the ecocoenotic patterns of the shrub layer formation, mathematically prove the influence of dominant species of the tree canopy (edifiers), and develop mathematical models of the reaction of the undergrowth to age-related changes in the forest. The research was based on the methods of system analysis, mathematical statistics, and ecological modeling using a digitized database covering 4115 forest taxation unities of the State Enterprise «Forests of Ukraine». To assess biodiversity, the Shannon-Wiener index was used, and to verify the hypothesis regarding the influence of the edifier, the non-parametric Kruskal-Wallis test was applied. It has been established that the species structure of the undergrowth is characterized by significant disproportion and is formed by several key species. The absolute dominant is Corylus avellana L., which occupies an area of over 5740 hectares. The highest complexity and stability of communities are formed under the conditions of Ulmeta minoris and Fraxineta excelsioris formations. It is proved at the highest level of significance (p < 10-22) that the density of shrubs is controlled by the dominant species of the tree layer: light-demanding species (Pinus sylvestris L., Fraxinus excelsioris L.) create an optimal phytoclimate. The development of shrubs has a non-linear age dynamics with phases of maximum development (10–40 years), intensive displacement (50–90 years), and stabilization (> 100 years). The developed multiple regression model proves a strict inverse dependence of the density of shrubs on the age and crown closure of the tree canopy (p < 0.001). The problem of biological invasions, which are a threat to native biodiversity, is highlighted separately: the spread of 5 alien species of shrubs was recorded on a total area of 515.8 hectares (4.02% of the coverage area), among which the main expansionist is Caragana arborescens Lam. (over 202 hectares), which changes soil chemistry and requires the development of special forestry measures for control
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