Phenology of pedunculate oak (Quercus robur L.) in the Zvolen basin, in dependence on bio-meteorological factors

Abstract

The paper presents the course of phenophases in pedunculate oak (Quercus robur L.) in the Zvolenská kotlina basin. The phenophases were observed according to the SHMÚ methodology. There were evaluated vegetative (leaf unfolding, bud-burst, leafing, autumn leaf discolouration, leaf-fall) and generative (flower buds, flowering, end of flowering, ripening of fruits) phenophases over 2003-2006, in relation to the bio-meteorological variables. The average day of onset of leaf bud swelling was the April 12, the blossoming phase began towards April 24. Significant for starting these phenophases was the mean daily air temperature not sinking below 0°C. The spring generative phenophases were launched when the effective air temperature was higher - at 8°C. The flower buds were observed towards May 6. The flowering started on about May 10. The autumn leaf discolouration started in average on October 9 and the leaffall on November 8. The beginning of these phenophases also depended on temperature and precipitation conditions in the growing season. The ripening of fruits was influenced by temperature and the rate of solar radiation, but it may be conditioned by genetic properties, too. Ripening of pedunculate oak fruits was observed towards September 19. The autumn phenophases finished sooner in dry years than in wet years.