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A preliminary study to compare Poaceae pollen data and to determine possible differences in pollen productivity and/or seasonality was performed at six locations in Catalonia (Spain): Barcelona, Bellaterra, Girona, Lleida, Manresa and Tarragona over a 6-year period (1996-2001). In the study area, Poaceae pollen grains are an important cause of respiratory allergies. Being present in the atmosphere all year round, the grass pollen concentrations are especially significant between May and August. The absolute peak occurs in June, except in Lleida where the peak comes earlier, possibly due to the early flowering of particular steppe species. Even if there are differences between different years, Girona and Lleida (inland locations) usually present the highest annual grass pollen index with, on average, 2177 pollen grains per year. Barcelona and Tarragona (the coastal sites) show the lowest levels, with around 1140 grass pollen grains per year. The respective local climates are very different, and pollen grains may originate in different grass species. A decreasing trend in the Poaceae annual pollen index was found over the period of the present study. [ABSTRACT FROM AUTHOR]

Since the beginning of aeropalynology, aerobiologists have tried to develop models able to predict the pollen load of the atmosphere to help physicians and patients suffering pollen allergies to improve the efficiency of pollen allergies prophylaxis. Some models have been developed by aerobiological services and are used for real time predictions, now provided online. They are statistical models and require the pollen load of the previous days as input, as well as statistics on the pollen load of the previous years, daily meteorological data and geographic information on the pollen sources. Here we propose to use process-based phenological models to predict the time course of the pollen load of the atmosphere using solely daily mean temperatures as input. The model proposed has been fitted and validated for 13 major allergenic taxa ( Alnus , Artemisia , Betula , Castanea , Corylus , Cupressaceae, Olea , Plantago , Platanus , Populus , Poaceae, Quercus and Tilia ) in different areas of France and Spain. The model has been integrated into a freeware called PPF (Positive Pollen Forecast), which will be made available from the 5 th Framework EU project POSITIVE web page at: http://www.forst.tu-muenchen.de/LST/METEOR/positive/. [ABSTRACT FROM AUTHOR]

Temperature is one of the main factors affecting the start of flowering in tree species that flower at the beginning of spring. Knowledge of the chilling and heat needs required by plants to overcome the period of dormancy enables us to determine the onset of pollination, which is of great importance to allergy sufferers. This study attempted to obtain behaviour models with a view to determining both the onset of the olive pollen season and daily pollen concentrations during the pollination period in Vigo. Monitoring was carried out using a Lanzoni VPPS 2000 pollen trap, from 1995 to 2002 inclusive. Olea pollen is mainly detected during the spring, principally in May. Given the geographical location, the very limited presence of this tree in the study area and the low Olea pollen concentrations detected in northern Spain as a whole, the values recorded here in the atmosphere of Vigo are particularly striking. A strong correlation was observed between total quantity olive pollen collected over the season and rainfall recorded during the second fortnight in February. According to the proposed model, an average of 680 Chilling Hours (CH) are necessary to overcome the chill period and break the state of bud dormancy, and 481 Growth Degree Days (GDD) °C are needed to induce flowering. Models for predicting daily mean pollen concentrations combine temperature and the previous days' pollen concentrations as predictor variables to provide a high level of prediction. [ABSTRACT FROM AUTHOR]