This diploma thesis reports on dynamic of the forest type group Abieto-Fagetum, at the lower vegetation level at Poľana mountain range. It is possible to find preserved original primeval forest systems at the Poľana area, which enable to observe the dynamic of forest climax. The ascertained data is possible to apply to the cultivation of cultural forests. The main aim of the thesis was to prove the presence of thermophylisation by measuring climate and conditions of plant community, which is the consequence of global climate changes. We founded 24 observational areas at selected spaces, where the phytocoenological records and climate quantities were carried out. The data proved that the primeval forest vegetation dynamic is more balanced than cultural forests dynamic. On the other hand, the thermal fluctuation is higher at cultural forests, and so is the dynamic fluctuation at plant community. The changes in plant communities appear to be caused by higher intensity of solar radiation. The influence of thermophylisation was not proved, as no occurrence of thermophillic plants was recorded. At the areas with missing woody plants or, more precisely at the areas with young forest cover; there was recorded the decrease of submontane species that indicate permanently humid soils. This may have been the consequence of humidity changes.