Monitoring of Vegetative Phenological Stages in European Beech (Fagus sylvatica L.) Growing in a Mixed Stand

The paper presents results of monitoring of beech (Fagus sylvatica L.) vegetative phenophases within the period of years 2005–2010 as related to results of evaluation involving data collected since 1991. This phenological study was performed in a young mixed forest stand situated in the Drahanská vrchovina uplands in the altitude of 625 m.a.s.l. Beginnings and duration of individual phenophases differed in dependence on the course of weather conditions in individual years of study. The highest variability was observed in the stage of budbreak. The obtained results indicate that the onset of spring phenophases was dependent on temperatures existing already in early spring and to the end of winter period. The statistical analysis proved a high correlation existing between the onset of spring phenophases on the one hand and soil and air temperatures on the other. Temperature requirements as defined for the beginnings of individual phenophases were evaluated on the base of cumulative sums of temperatures higher than 0 °C. The obtained results indicate that, as compared with results of long-term monitoring, the period of the duration of spring phenophases had been gradually shortened. On the other side, however, the duration of autumn phenophases was extended and they ended in the late autumn. Repeated extensions of the growing season to the detriment of winter dormancy might show a negative effect on the health condition of forest stands.