Flowering phenology of olive trees (Olea europea L.) in North Sardinia (Italy) and its relationships with airborne pollen pattern

Aeropalinology and phenology study different natural phenomena. Aeropalinology is the scientific discipline focused on the presence and distribution patterns of pollen in the air, whereas phenology studies the timing of periodic biological phenomena and their relationships with the environment. Because the presence of pollen in the air is related to the release of pollen from anthers and, consequently, to reproductive cycle of plants, the two disciplines are often interconnected. Information on relationships between reproductive phenology of species and their airborne pollen curves have important implications not only in allergology but also in phenological and climatological studies. If airborne concentration pattern reflects flowering phenology of a given species, it may represent a sensitive regional indicator in climate change studies and it might be used instead of long-term phenological observation series. In this paper the results of aeropalinological and phenological studies on Olea europea L. (olive) are presented. The main aim of this research was to investigate relationships between flowering phenology of olive and its airborne pollen seasonal pattern. In particular this study was carried out in order to: i) verify the synchronization between the release of pollen from anthers and its occurrence in the atmosphere, and ii) evaluate the effect of the environment on pollen release and dispersion. From April to June, phenological observations were carried out every day on three olive trees; for each individual three one-year shoots were selected for each cardinal point of the crown for a total of 12 shoots per plant. Airborne olive pollen concentration was recorded both in the olive grove and in an urban area located 5 km from the olive grove. Meteorological parameters were also recorded during the experimentation. The results of this study showed that meteorological parameters influenced daily air pollen concentration seasonal pattern by the changes in flowering rhythms. A clear correspondence between the full flowering stage date and the airborne pollen concentration peaks was also observed both in the grove and in the urban area.