Variation of spring phenological phases and airborne pollen grains of the european hazel (corylus avellana l.) in the Zvolen Basin (Slovakia) as influenced by meteorological factors

The impact of air temperature on the formation of generative organs of the European hazel (Corylus avellana L.) and the onsets of related phenophases during the years 1987-2009 in Central Slovakia (the Zvolen basin) are analyzed in this paper. The analyses are based on the records of 10% and full onset of catkins lenghtening, inflorescence emergence and flowering. Catkins lengthening was observed on February 7th and lasted 10 days on average, inflorescence emergence on February 20th and 8 days and flowering on March 2nd and 6 days. The earliest dates of phenophases onsets were observed in 2007, while the latest in 1987 and 2005. A large variability of daily mean air temperatures in different years resulted also in a high variability of phenophases onsets (sx% 27.3-35.3). The onsets of spring phenophases earlier by 2.5-5.5 days were recorded at the end of the evaluated period of years as compared with the beginning. The concentration of pollen grains captured with a Burkard volumetric rotate pollen trap culminated approximately 10 days after flowering. The peak pollen grain concentration varied in a range of 50-500 pollen grains per m3. The peaks of pollen grains concentrations in the Zvolen Basin were influenced, apart from the flowering of the European hazel also by the transport of pollen grains from higher mountainous habitats especially in the late pollen season