Meteorological factors driving airborne grass pollen concentration in central Iberian Peninsula

Abstract

Grasses are a taxonomic group of considerable environmental importance, playing a major ecological role as well as making a significant contribution to the world’s economy, since they include valuable crop and pasture species. Grass pollen allergens are also among the main causes of respiratory allergies worldwide. The interpretation of airborne grass pollen concentrations is a particularly complex task, given the marked diversity of pollen-emitting species and the influence of weather-related variables. This paper examines the influence of meteorological variables on flowering in the species contributing most to airborne grass pollen concentrations. This study was carried out in the surroundings of the city of Toledo (Spain), a Mediterranean city located in the center of the Iberian Peninsula. Temperature was the variable most influencing flowering onset, which was also affected by relative humidity, rainfall and hours of sunlight. The flowering period of grass species that flower at the start of spring (Bromus rubens and Hordeum leporinum) began earlier in years with higher mean winter temperatures, while the species that flower from mid to late spring (Trisetaria panicea and Dactylis glomerata subsp. hispanica), the flowering period began earlier in years with higher cumulative rainfall in winter and spring, which were also the years with the highest mean temperatures. Research into the influence of weather-related variables on grass phenology can shed important light on variations in airborne pollen concentrations, which determine the potential period of exposure for allergy sufferers.