Aerobiology of Fagaceae pollen in Trieste (NE Italy)

The aerobiological behaviour of Fagaceae in Trieste and the correlations with the meteorological parameters were examined. Airborne pollen grains of Castanea, Fagus and Quercus were collected from 1990 to 2003 using a Hirst type spore trap. The main pollen season (MPS) takes place in April and May for Quercus and Fagus, in June and July for Castanea. The highest values occur in year 1993 for Quercus, in 1998 for Castanea and in 1992 for Fagus. The Fagaceae content of the air is mainly due to Quercus and Castanea pollen, Fagus usually having a scarce pollen shedding in Trieste. The highest counts of Fagaceae pollen grains are found from late April to mid May and are mainly due to the pollen shedding of oaks. The cumulative counts vary over the years, with a mean value of 2.719 pollen grains, a lowest total of 1.341 in 2002 and a highest total of 4.704 in 1993. No positive nor negative long-term trends in pollen shedding are found. No cyclic variations were observed. Spearman’s correlation was used to establish the relationship between the daily pollen counts and the daily meteorological data. Daily pollen concentrations present sometimes positive correlation with temperature, negative with rainfall and wind speed, and no correlation with humidity. Fagus and Quercus start dates result positively correlated between themselves. Significant correlations are found between the start of MPS and the mean and maximum temperature in March for Fagus and Quercus, and May for Castanea.