Incidence of Echium pollen in the Middle West of Iberian Peninsula: an unusual flowering period and its significance in aerobiological studies

Abstract

We analysed the occurrence of the Echium pollen in the atmosphere of Salamanca, on the basis of 8-year observation (2000–2007) with the aim to evaluate its aerobiological behaviour. Aerobiological samples were collected by the Hirst volumetric method with a 7-day Burkard spore trap. The atmospheric pollen season of Echium was observed in late spring (May and June), showing also high levels in midday hours. However, an anomalous flowering period was detected in late autumn and early winter between years 2006 and 2007 and it could be connected with high daily temperature registered in October 2006 in comparison with the 2000–2005 period and its particular increasing tendency similar to those detected in the preceding month of the late spring flowering period. Statistical analysis by means of the Spearman’s non-parametrical test and linear regression analysis reflected a positive correlation with temperature and a trend to increase in daily temperature during late October 2006 and April in 2000–2005 with similar indexes (R2 = 0.50, R2 = 0.58, respectively). In conclusion, aerobiological data could contribute to the development of further studies in order to a better understanding of different plant species phenology.