Forecast models and trends for the main characteristics of the Olea pollen season in Nice (south-eastern France) over the 1990–2009 period

Abstract

The olive tree, Olea europaea, is very common in the southeast of France and its pollen is recognised as one of the most important allergenic in the Mediterranean. This study allowed for the development of predictive models to calculate the main characteristics of the Olea pollen season over the last 20 years from a wide range of meteorological variables. Clear evidence of the relationship between the main features of the Olea pollen season and the temperature recorded during the months before the flowering period could be demonstrated. The mean temperature in February plays an important role in determining reproductive growth and anthesis. It seems that the mean temperature during autumn influences the pollen index of the next year's pollen season. Other environmental factors, such as global radiation and rainfall, may be of great influence in determining the onset and final date of pollination. The accumulated rainfall amount during the pollination period has a negative effect on the pollen index. This may be interpreted as the wash out of airborne pollen by raindrops. However, rainfall during the vegetative period has a positive effect on pollen production. The pollen quantities depend not only on meteorological conditions before pollen release, but also maybe on those prevailing during pollen release. Finally, we could demonstrate an upward trend in annual pollen production and a stability of the mean duration of the Olea pollen season. The increase in Olea pollen abundance coincides with a rise in air temperature over the last 20 years.