Synchronized inter‐annual fluctuation of flowering intensity affects the exposure to allergenic tree pollen in North Europe

Abstract

Many anemophilous, early-flowering tree genera include allergy plants of world-wide significance. We studied the synchronisation of high and low pollen years in the genera Betula, Alnus, Corylus, Salix and Populus and the cumulative effects that an increasing number of taxa has on the number of days of exposure to different levels of allergenic pollen in North Europe. The proximal causes of the inter-annual variations of airborne pollen loads were analysed with a multiple regression analysis. The annual fluctuations of airborne pollen sums were compared between genera and found to be positively correlated among all combinations of genera at the three study sites. Most correlations were statistically significant (pv0.05). The comparison between Betula and Alnus is discussed first. Betula pollen was clearly the most abundant airborne pollen type. The presence of Alnus pollen, however, significantly increased the predisposal to allergenic pollen. At all sites, the number of days per year when the Betula and Alnus pollen counts together exceeded 10 and 100 grains m 23 of air, was found to be greater than the number of days when the Betula pollen counts alone exceeded 10 and 100 m 23 of air. The difference was statistically significant. In Kuopio, the difference was found to be statistically significant even for grains per 1 000 m 23 of air of Betula and Alnus together compared with the same count of Betula pollen alone. Betula, Alnus and Corylus belong to the order Fagales and have cross-reacting main allergens. The flowering of Alder and Corylus culminate at the same time, two to four weeks earlier than that of Betula. Due to synchronization of high and low years and the mostly non-overlapping flowering seasons, the time of exposure to pollen may be very long during the high years. Furthermore, Alnus and Corylus pollen may prime allergic people before the onset of the Betula season.

Male flowering of birch: Spatial synchronization, year-to-year variation and relation of catkin numbers and airborne pollen counts

“…The weather conditions during the growing season and resource allocation within the tree have been identified as being important proximal factors affecting the intensity of birch pollination in many studies (Dahl and Strandhede, 1996;Masaka and Maguchi, 2001;Ranta et al, 2005;Ranta and Satri, 2007). The effect of weather parameters was observed also in the current study.…”

“…Synchronous fluctuations have been observed to involve not only populations of one tree species, but even different species and families (Ranta and Satri, 2007;Schauber et al, 2002;Shiabata et al, 1998Shiabata et al, , 2002. Extensive fluctuations in flowering are characteristic of trees belonging to the Betulaceae family.…”

Pollen season of European beech (Fagus sylvatica L.) and temperature trends at two German monitoring sites over a more than 30-year period

“…Synchronized inter-annual fluctuations of flowering intensity can cover large geographical areas, and they can even occur among different tree genera, e.g. Betula, Alnus (alder) and Corylus, resulting in high concentrations of many different allergenic pollen in the same year (Ranta and Satri 2007). Kasprzyk et al (2014) determined a 3-year cycle of mast years of European beech.…”

The Onset, Course and Intensity of the Pollen Season

“…Similarly, the amount of rainfall during the rainy season of the year previous to fl owering is positively correlated to the annual pollen sum for oak in northern California (reference in Antepara et al 1995 ) . In North Europe, a number of studies show the importance of the weather conditions during the previous growing season for the intensity of birch fl owering (Emberlin et al 1993 ;Dahl and Strandhede 1996 ;Rasmussen 2002 ;Ranta et al 2005 ;Ranta and Satri 2007 ) . Emberlin et al ( 1993 ) used pre-seasonal meteorological parameters as independent variables in a multiple regression model.…”