DYNAMICS OF SPECIES COMPOSITION IN THE HERBACEOUS-SUBSHRUB LAYER OF PEDUNCULATE OAK (QUERCUS ROBUR L.) PLANTATIONS FOLLOWING CANOPY CLOSURE IN A MOIST, RELATIVELY FERTILE SITE TYPE IN ZHYTOMYR POLISSIA

Abstract

Background. In recent decades, the area of mature oak forests in Ukraine has been declining due to clear felling. Additionally, the existing network of protected areas is insufficient to encompass the full diversity of natural oak forests. Given these challenges, research is needed to assess plant diversity in forest plantations of different ages established after clear felling, based on forest site type classification.
Materials and Methods. The research was conducted in the Dyvlyn Forestry, part of the Branch “Luhyny Forestry” of the State Specialized Forest Enterprise “Forests of Ukraine” in Zhytomyr Region, Ukraine. The species composition was examined in pedunculate oak (Quercus robur L.) plantations of different ages (10 years and 60 years) and old-aged natural forests (120 years) in moist relatively fertile forest sites. Geobotanical, forestry, and silvicultural methods were employed for data collection and analysis.
Results. This study determined the species composition of herbaceous and subshrubby plants in a 120-year-old natural oak forest Quercetum (roboris) franguloso (alni) cаricosum (brizoides). The herbaceous-subshrub layer exhibits considerable species diversity, with 15–28 species in 120-year-old natural oak forests, 35–47 species in 60-year-old plantations, and 35–51 species in 10-year-old plantations.
Conclusions. The projective ground vegetation cover was found to be 80–90 % in 120-year-old oak stands and 80–85 % in 10-year-old plantations. The results indicate a predominance of forest species in all stands, with the lowest proportion recorded in 10-year-old plantations (68 %). In contrast, 60-year-old plantations and mature oak forests exhibited nearly identical proportions of forest species (91 and 90 %). The Sørensen similarity index between the herbaceous-subshrub species composition of 10-year-old plantations and 120-year-old forests was 0.51, increasing to 0.66 when comparing 60-year-old plantations with mature stands. The advance regeneration of tree species comprised 6–8 species in 10-year-old plantations, 4–5 species in 60-year-old plantations, and 5–7 species in mature oak forests. It was found that the understory (shrub species) closure varied, reaching 50 % in 10-year-old plantations, 40–50 % in 60-year-old plantations, and 50–60 % in the natural oak forest.