Impact of climate change on the pollen season on relevant species in Iberian’s dehesa: a case study of Fraxinus sp.

Abstract

The allergenic nature of ash (Fraxinus sp.), an important element of the dehesas, has been poorly studied in meridional Europe owing to the low concentrations of this pollen type in the atmosphere. However, it has cross-reactivity with Olea L. and other homologous allergens of trees and herbaceous species, leading to earlier and more prolonged respiratory allergenic symptoms. The main aims of this work were to characterize the main pollen season (MPS) of ash from 2011 to 2022, to evaluate the influence of meteorological variables on airborne concentrations of this pollen type and to elaborate a pollen calendar for Fraxinus in Salamanca. The aeropalynological analysis for the eleven years of the study shows that the MPS for Fraxinus begins on 27 th December until 4 th April with an average duration of 100 days, a mean peak value of 57 grains/m³ reached on 22 nd February and a mean annual pollen integral of 567 grains/m³, observing an earlier onset of MPS, an increase in its duration and a decrease in its concentrations, presumably linked to climate change. Regarding the influence of meteorological parameters on pollen concentrations, positive correlations were found for maximum and mean temperatures and insolation, as well as southeast winds and frequency of calms, while negative correlations were reported for precipitation, relative humidity, and wind speed. The analyze of Fraxinus pollen could be used to predict seasonal behavior and warn people who may suffer pollinosis either from ash pollen or from cross-reactivity events.