The presented diploma thesis deals with the evaluation of the spring phenological phases onset at the experimental site in the NR Boky depending on the changing environmental conditions. Analysis of the phenological phases in the period 2009 – 2018 was conducted on four woody plant species: European cornel (Cornus mas L.), Blackthorn (Prunus spinosa L.), Hawthorn (Crataegus monogyna Jacq.) and European hazel (Corylus avellana L.), at which unfolding and flowering were selected. The main aim of the thesis was the evaluation of the course of selected phenological phases in relation to average two-months temperature before the onset measured at meteorological station Boky – south. The correlation between the air temperature and the onset of phenological phases was confirmed in all of the selected species as well as their shift to an earlier date. For examination of the changes current phenological data were compared with the historical phenological observations in the years 1931 – 1960. In comparison with historical data the onset shifts by 32 – 39 days in vegetative and 3 – 11 days in generative phenological phase depending on plant species. This shift is mainly caused by the air temperature increase in the period before the phenophases onset. According to climate scenario RCP 6.0 the increase of average annual air temperature by 2,9 °C is expected. Continuing air temperature increase will probably accelerate the phenological phases onset, which could have major impact on the natural ecosystems.