ALNUS POLLEN DEPOSITION IN THE ROZTOCZE REGION ( SE POLAND ) WITH RELATION TO VEGETATION DATA

Pollen deposition of alder has been measured at ground level by means of nine modifi ed Tauber traps in different plant communities according to rules of the Pollen Monitoring Programme (http://pmp.oulu.fi ). The series of data covers the period 1998-2006. The area under investigation is situated in the Roztocze (surroundings of the Guciów village) within the protective zone of the Roztocze National Park. During nine years of monitoring, signifi cant variations were observed between single years of deposition. The occurrence of peak years (1998, 2001, 2003 and 2006) connected with higher production of Alnus pollen was observed at many pollen monitoring sites, but its relationship with different proportions of alder within the surrounding vegetation seems rather weak. The average value of annual pollen deposition of Alnus for the whole region was calculated at ca. 1370 grains . cm-2. At the sites situated within the open landscape, pollen infl ux values ranged from 442 (in 2005) to 6894 (in 1998). It seems that other factors than the proportion of alder within the vegetation control the deposition of Alnus pollen. Long-distance transport and meteorological factors such as wind speed and direction should be taken into account in future studies.


INTRODUCTION
In Poland three species of Alnus Mill.genus occur, from among which the most widespread is common alder Alnus glutinosa /L./ Gaertn.(Z a j ą c and Z a j ą c , 2001).As an anemophilous tree belonging to the Betulaceae family, common alder produces a great amount of pollen triggering allergic reactions.For that reason, it arouses interest of aerobiologists and allergists.In our country Alnus pollen appears in the air very early, often in the fi rst decade of February (K a s p r z y k et

Situation of pollen traps against alder communities
The distance between the pollen trap and the nearest fl owering Alnus trees differs very signifi cantly at individual sites.Alder trees appear the closest to the trap (40 m) at the site 2 (to SE and NE directions from the pollen trap).They grow along the forest edge, in wet meadow.A patch of alder carr of Ribeso nigri-Alnetum association occurs also very close (100m) to the trap 4 (Fig. 2).The distances at other pollen-trapping sites are much greater.Table 1 contains a brief description of the sites and the approximate distance from the nearest alder trees.
The two sites (6 and 7) are intended to be "regional" ones to gather not only local but also regional pollen rain coming from outside the local vegetation.They were situated in open landscape within cultivated and abandoned fi elds.

Pollen data
Pollen deposition of Alnus differed very signifi cantly in individual years and between the sites.The differences between the sites were much smaller than between PI values in different years at the same site.The years of high pollen deposition (1998, 2001, 2003 and 2006) were observed, as well as the years of very low  (1999, 2000 and 2005) and average deposition (2002 and 2004).Pollen infl ux values for alder calculated for all nine trapping sites in the years 1998-2006 are presented in Table 2.
The average value of annual alder pollen deposition for the study area was calculated at 1368 grains cm -2 .It was based on all the results from the pollen-trapping sites during nine years of monitoring.This value is more accurate than the fi rst rough estimates (1419 Alnus pollen grains cm -2 annually) based on four years' data (P i d e k , 2004).In the peak years, the PI values signifi cantly surpassed the average deposition.In 1998 the highest among average values was recorded, i.e. over 4300 Alnus pollen grains cm -2 (Fig. 3).However, taking into account that only three traps survived the fi rst season of pollen monitoring, the result should be treated with limited confi dence.In 2000 the lowest average value (365) of pollen deposition was recorded.In this case, the two regional traps were damaged which could infl uence the PI values quite signifi cantly.
Taking into account the average values of Alnus pollen deposition at each of the monitoring sites (Tab.2), the highest PI was recorded at the sites 6 and 4 situated quite close to the patch of alder carr.The alder trees

DISCUSSION
Considerable differences in the values of Alnus pollen deposition in particular years are not surprising in the present investigations in the Roztocze region.They undoubtedly result from the diverse pollen production conditioned by many factors.Several years' monitoring of pollen deposition in Cracow by means of gravimetric method indicated that annual pollen sums of Alnus fl uctuated between 359 and 1749 (Szczepanek, 2006).Peak and low years were recorded also in two cities, i.e.Lublin and Rzeszów, located in the regions adjoining the Roztocze from the north and the south, in which aerobiologic monitoring was conducted by means of volumetric method.The comparison of annual pollen sums recorded in Lublin, Rzeszów and in the Roztocze reveals rather great conformity in the occurrence of years with high and low pollen production of this taxon (K a - Although as a rule the peak years were followed by low or average-deposition ones in the Roztocze, it should be stressed that biannual rhythm of abundant deposition of alder pollen did not unambiguously appear in the analysed period (1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006).Its occurrence was discussed among others by Spanish aerobiologists (R od r i g u e z -R a j o et al. 2004) who suggested that some taxa fl owering in winter, such as alder, reveal approximately biannual rhythm of abundant pollen production, though sometimes a year of abundant production of Alnus pollen is preceded by two years of low production (A i r a et al. 1998).
Analysis of pollen infl ux in particular sites indicated that the deposition of alder pollen reached the highest values several times at the sites 4 and 6 (mostly during the peak years) and at the sites 3 and 9 (mostly during the low years).The fi rst site is situated close to the association of Ribeso nigri-Alnetum, i.e. at a distance of 100 m.Therefore, in this case the proximity of alder carr might be the main factor infl uencing the PI.At the sites 3, 6 and 9 (situated at a distance of 400-900m from the alder communities), we should search for other explanation of high PI values.Sporadically, the highest PI values occurred also at the sites 5, 7 and 8 where the distance from the nearest Alnus communities ranged from 200 to 500 m.
Surprisingly, only twice the highest PI was recorded at the site 2 where the nearest alder trees grow very close to the trap (40 m).
Thus, the relationship between the value of Alnus pollen deposition and the proportion of alder in vegetation communities surrounding the pollen trap seems to be rather weak.Alder pollen infl ux probably represents local trees to a low degree, and it depends largely on regional vegetation.Alnus pollen comes mostly from large patches of alder communities growing in the Wieprz River valley.It seems that transport from the valley environs can be the most important factor controlling the spread of alder pollen.This can be favoured by strong winds occurring mostly in colder seasons of the year (K a s z e w s k i et al. 2002).Pollen grains must be transported upslope, as the sites 6, 8, and 9 occur in the highest positions over the valley, i.e. several dozen metres above the upper terrace of the Wieprz River.Both the surrounding vegetation and the distance from alder communities are different in the case of each mentioned site.
Landscape openness certainly favours the spread of pollen.Such situation occurs in the instance of the sites 6 and 7, though pollen reaching the site 7 has to clear a small obstacle of a pine-birch tree patch.However, even the occurrence of beech forest in close (several metres) or more distant (100 m) vicinity of the trap does not seem to be a signifi cant obstacle for penetration of alder pollen.In the period of alder fl owering, beech trees are still leafl ess, so winds of different directions can transport masses of alder pollen to different places.That is why the highest values of PI were recorded in particular years at different sites.The lowest values are usually found in the site 1 that is situated not far from the alder communities, but in a small clearing within dense fi r forest which can stop most of penetrating alder pollen.Probably for the same reason, very low deposition was observed at the site 2 in the years 1999, 2001, 2002 and 2006.The importance of long-distance transport concerning plants fl owering early in spring was also confi rmed by observations from different regions in Poland (K as p r z y k et al. 2004) as well as from other countries where alder pollen was found over 200 km away from its source area (S u s z k a , 1980).
Pollen grain of alder is much smaller than the grains of coniferous trees, and the difference in fall speed is also considerable.The comparison of pollen productivity estimates after B r o s t r ö m (2002) for Alnus (4.2), Betula (8.9), and Pinus (5.7) shows that alder trees are almost as effi cient producers of pollen as pine trees.These values were used in modelling of source areas of pollen (S u g i t a et al. 1999) and stand in agreement with Andersen's (1970) investigations in Danish forests.The comparison of fall speeds of pollen grains of these three taxa (E i s e n h u t , 1961), which are for alder -0.021, birch -0.024, and pine -0.031, also shows that alder pollen can be long-distance transported.These distances can be comparable to those at which pine and birch pollen is transported on a large scale.The preliminary estimation of a source area of pine pollen in the Roztocze region indicates that a considerable amount of pollen comes from the areas over 30 km away from pollen traps (P o s k a and P i d e k , 2007).Therefore, it is not surprising that the highest values of alder pollen deposition are recorded not always in the same traps, and not always in traps situated closest to alder trees.Such incidental factors as wind direction, air currents, and precipitation have stronger infl uence on alder pollen deposition.Analysis of meteorological factors infl uencing Alnus pollen production and dispersal can shed light on the solution of this particular problem.(1998,2001,2003,2006), co związane jest ze zwiększoną produkcją pyłku Alnus.Zjawisko to odzwierciedla się zwykle na wielu stanowiskach, ale związek depozycji pyłku z udziałem olszy w składzie roślinności wydaje się raczej słaby.Średnia roczna wartość rocznej depozycji pyłku Alnus obliczona dla całego regionu wynosi około 1370 ziarn cm -2 .Na stanowiskach znajdujących się w otwartym krajobrazie wartości pollen infl ux wahały się w analizowanym okresie od 442 (w 2005 roku) do 6894 (w 1998 roku).Wydaje się, że inne czynniki niż procentowy udział olszy w roślinności kontrolują depozycję pyłku Alnus.W przyszłych badaniach należałoby wziąć pod uwagę wpływ dalekiego transportu pyłku oraz czynniki meteorologiczne takie jak m.in.prędkość i kierunek wiatru.

Dziewięcioletnie pomiary opadu pyłku
al. 2004; S z c z e p a n e k , 2006; S m i t h et al. 2007; W e r y s z k o -C h m i e l e w s k a and P i o t r o w -NINE-YEAR RECORD OF ALNUS POLLEN DEPOSITION IN THE ROZTOCZE REGION (SE POLAND) WITH RELATION TO VEGETATION DATA Irena Agnieszka Pidek Institute of Earth Sciences, Maria Curia-Skłodowska, University in Lublin, Al.Kraśnicka 2 c/d, 20-718 Lublin, Poland e-mail: ipidek@biotop.umcs.lublin.plReceived: 02.10.2007s k a , 2004; 2006).Due to cross reactivity of alder and birch pollen, not only the concentration of Alnus pollen has been analysed, but also the course of pollen seasons and related meteorological factors (G i o u l e k a s et al. 2004; K a s p r z y k et al. 2004; R o d r i g u e z -R a j o et al. 2006; S m i t h et al. 2007).Pollen seasons of early spring fl owering taxa, such as Alnus and Corylus, are quite sensitive to the increase in global air temperature.Thus, these taxa are important in the context of global climate change (E m b e r l i n et al. 2007; R o d r i g ue z -R a j o et al. 2004).There is also a palaeoecological aspect of the studies on alder pollen.Analysis of its deposition at the ground level, in situations analogous to deposition in mid-forest mires in the past, can shed light on the problem of the Holocene expansion of alder.Isopollen maps indicate that it occurred in two stages.The fi rst stage, about 8500 C 14 years BP, is related to the migration of Alnus incana along the Vistula River valley.Alnus glutinosa was probably responsible for the second expansion wave about 8000 C 14 years BP (S z c z e p a n e k et al. 2004 s p r z y k , 2006; P i d e k et al. 2006; W e r y s z k o --C h m i e l e w s k a and P i o t r o w s k a , 2006).

Table 1
Description of pollen-trapping sites in the area under investigation.