ANALYSIS OF ALNUS spp. POLLEN SEASONS IN LUBLIN AND WARSZAWA (POLAND), 2001-2007

The course of Alnus spp. pollen seasons was compared in two cities, Lublin and Warsaw, located at a small distance from each other but included in different climatic regions of Poland. The studies were conducted using the volumetric method. It was shown that Alnus pollen seasons started in Warsaw earlier and were much shorter than in Lublin. The span between the start dates of pollen seasons was similar and it was 53-54 days. Peak days occurred in both cities most often in the second decade of March, but in Warsaw they were recorded several days earlier. Maximum concentrations reached higher values in Lublin, whereas annual totals were higher in Warsaw. The number of days with the concentration > 50 pollen grains m-3 per 24 hours was 5-27 days for Warsaw and 10-19 days for Lublin over 7 years of study.


INTRODUCTION
In Poland three species from the genus Alnus and their hybrids occur (Seneta and Dolatowski, 2007).Alnus glutinosa L. and A. incana L. trees grow in the lowland and in lower mountainous areas, whereas A. viridis shrubs are noted only in the Western Bieszczady Mountains (S z w e y k o w s k a and S z w e y k o w s k i , 1993; Z a j ą c and Z a j ą c , 2001).The two former species grow on water edges and lowland bogs, forming a swampy type of deciduous forests called alder woods of great ecological signifi cance.Alnus incana is a pioneer species used in the recultivation of post-industrial areas (S e n e t a and D o l a t o w s k i , 2007).Alder populations are currently endangered due to the lowering of ground water levels (M e j n a r t o w i c z , 2007).
Alder pollen grains are transported by the wind for long and very long distances.It is favoured by their small size and the low falling velocity.Studies conduc-

MATERIALS AND METHODS
The course of Alnus pollen seasons in Lublin and Warsaw was studied in the years 2001-2007.Airborne pollen counts were conducted using the volumetric method by means of a VPPS Lanzoni 2000 pollen trap (H i r s t 1952).In Lublin, the trap site was located in the city centre on a building roof (51 0 14'N, 22 0 32' E) at a height of 18 m, whereas in Warsaw in the Bielany district (52 0 15'N, 21 0 00'E), 27 m above ground level.The distance between the cities is 176 km.
The pollen concentration was expressed as the number of pollen grains m -3 per 24 h.The beginning and the end of the pollen season was determined using the 98% method, that is, the period was determined retrospectively when 98 percent of Alnus pollen grains occurred in the air (E m b e r l i n et al. 1993).
Dynamics of the pollen seasons (Figs 5, 6) was presented on the diagrams proposed by L a t a ł o w a et al. (2002).In both cities, at a distance of 2-4 km from the trap site, alders grow along river banks, also forming larger tree clusters.

RESULTS
In the years 2001-2007, the start of the Alnus pollen season, determined using the 98 % method, fell in the period between 2 February and 28 March in Lublin, whereas in Warsaw in the period between 4 February and 29 March.The date of the beginning of the pollen season for this taxon in the years 2006 and 2007 in Lublin and in Warsaw was very similar, whereas in the remaining years the difference was 6-16 days (Tab. 1, Fig. 1).
After the calculation of averages for the study period, it was found that the Alnus pollen season started earlier in Warsaw than in Lublin by 2 days using the 98% method (Tab.2) and by 5 days using the 100% method.
Alnus pollen seasons were much shorter in Warsaw than in Lublin, except for the year 2001 (Fig. 2).The length of the pollen season in Lublin ranged between 27 and 80 days, whereas in Warsaw between 14 and 51 days (the 98% method) (Tab.1).The average length of the Alnus pollen season for the seven-year period was 35 days for Warsaw, and for Lublin 48 days (the 98 % method) (Tab.2).
Maximum concentrations of Alnus pollen grains were noted in Lublin between 5 March and 2 April, whereas in Warsaw between 17 February and 2 April (Tab.1).The average date of the maximum Alnus pollen concentration from the seven-year period was 4 days earlier in Warsaw than in Lublin (Tab.2).
In Lublin, maximum Alnus pollen concentrations in the seasons were generally higher than in Warsaw, in particular in the last four years (Tab.1).The sevenyear average of this parameter was 46 percent higher for Lublin (Tab.2).

Table 1
Characteristics of Alnus pollen seasons in Lublin and Warsaw in the years 2001-2007 (98% method).

Table 2
Comparison of of Alnus pollen seasons in Lublin and Warsaw, an average from the years 2001-2007.