Long-distance transport ofBetula pollen grains and allergic symptoms

Summary An example of the potential importance of air masses as carriers of aero-allergens from distant source areas is provided. Considerable amount ofBetula pollen is relatively often transported to Fennoscandia before the local birch flowering period, mainly by southeastern air masses from eastern part of central Europe. Although the distance and the transport time in some cases can be extensive, the pollen grains seem to cause allergic reactions among sensitive persons.A comparison between the clinical results andBetula pollen counts from the time before the local flowering season in Stockholm in 1989 is presented.     

Annual pollen spectrum variations in the air of Bratislava (Slovakia): years 2002–2009

Pollen grains in the atmosphere of Bratislava were quantitatively and qualitatively analysed during an 8-year period (2002–2009) using a Burkard volumetric pollen trap. The mean annual total pollen grain count recorded during this period was 36,608, belonging to 34 higher plant taxa (22 trees and/or shrubs and 12 herbaceous species). The maximum annual total pollen grain count (50,563) was recorded in 2003 and the minimum (14,172) in 2009. The taxa contributing the highest concentration of pollen grains were Betula, Urticaceae, Cupressaceae-Taxaceae, Populus, Pinus, Poaceae and Ambrosia. During the study period, there was a remarkable increase in the number of pollen grains from February to April, with the highest daily mean pollen counts recorded in April. Total pollen concentration began to decrease markedly in May, but there was a second increase between July and August, followed by a decrease in September. The timing and length of the pollen seasons varied. Betula and Poaceae showed a rather constant 2-year fluctuating rhythm. The relationships between airborne pollen concentration and meteorological variables were assessed. Based on these results, the first pollen calendar in Slovakia has been constructed for the area of Bratislava, which provides a great deal of useful and important information.     

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

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 (p<0.05). 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^?3 of air, was found to be greater than the number of days when the Betula pollen counts alone exceeded 10 and 100?m^?3 of air. The difference was statistically significant. In Kuopio, the difference was found to be statistically significant even for grains per 1?000?m^?3 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.     

Are the birch trees in Southern England a source of <Emphasis Type="Italic">Betula</Emphasis> pollen for North London?

Birch pollen is highly allergenic. Knowledge of daily variations, atmospheric transport and source areas of birch pollen is important for exposure studies and for warnings to the public, especially for large cities such as London. Our results show that broad-leaved forests with high birch tree densities are located to the south and west of London. Bi-hourly Betula pollen concentrations for all the days included in the study, and for all available days with high birch pollen counts (daily average birch pollen counts >80 grains/m³), show that, on average, there is a peak between 1400 hours and 1600 hours. Back-trajectory analysis showed that, on days with high birch pollen counts (n = 60), 80% of air masses arriving at the time of peak diurnal birch pollen count approached North London from the south in a 180 degree arc from due east to due west. Detailed investigations of three Betula pollen episodes, with distinctly different diurnal patterns compared to the mean daily cycle, were used to illustrate how night-time maxima (2200–0400 hours) in Betula pollen counts could be the result of transport from distant sources or long transport times caused by slow moving air masses. We conclude that the Betula pollen recorded in North London could originate from sources found to the west and south of the city and not just trees within London itself. Possible sources outside the city include Continental Europe and the Betula trees within the broad-leaved forests of Southern England.     

Flowering phenology and airborne pollen grains of chosen tree taxa in Rzeszów (SE Poland)

The aim of the study was to compare the courseof flowering and the occurrence of Alnus,Corylus and Betula pollen grains inthe air in 1999–2001. In 2000 and 2001 birchesflowered in a typical way – the floweringperiod was short and intense and that periodhad the highest concentration of pollen. Bothyears had no rainfall then and the temperaturewas high, which caused intense flowering ofbirches over a large area. In 1999 and 2000most of the Alnus and Coryluspollen was recorded at the end or after theirflowering period. At that time the weather wasunstable (as is usual in February and March).Pollen must have been transported fromelsewhere. Wind analysis showed that the mainsources of Corylus pollen must have beenin the south, and of Alnus in the southand west. In the southern margin of Poland thevegetative period begins later due to a colderclimate.     

Pollen‐vegetation relationship and pollen preservation on the Northeastern Qinghai‐Tibetan Plateau

Qinghai‐Tibetan Plateau is one of the most sensitive areas to climate change of the earth, owing to its unique topographic features and ecosystem. Soil pollen analysis is an important component of palaeo‐ecological research, while pollen preservation and the relationship between pollen and vegetation can influence the correct interpretation of fossil pollen spectra. In this paper, 36 pollen samples, which come from four meadows and two forest soil pollen profiles, have been analyzed to determine relationships between pollen and vegetation and pollen preservation on the northeastern Qinghai‐Tibetan Plateau. The relationship between pollen and vegetation shows that the surface pollen assemblages can represent regional vegetation characteristics moderately, while Betula and Populus pollen is absent in the soil surface for Betula and Populus mixed forest. Artemisia, Chenopodiaceae, Ephedra, Pinus, Hippophae etc. are over‐represented pollen taxa, Leguminosae, Ranunculaceae, Rosaceae, Gramineae etc. are under‐represented pollen taxa. The study of pollen preservation indicates that pollen concentrations decrease with the increase of soil depths, more pollen taxa are present in surface soils than in deep levels, and more than 75% pollen grains will be lost from the surface soils to deep levels. Pollen sorting preservation function should be noticed. Artemisia and Chenopodiaceae can be preserved well and have higher pollen percentages in deeper levels. Cyperaceae and Populus are preserved worse, Populus pollen is absent and Cyperaceae has higher pollen percentages in the surface soil than in the deep levels. The high soil pH values are the most destructive factors for pollen preservation on the northeastern Qinghai‐Tibetan Plateau. Pollen concentrations decrease sharply when the soil pH values are over 7.6. Downward leaching of pollen is unimportant in this study.     

Airborne pollen and spores on the Arctic island of Jan Mayen

A survey of airspora collected on Jan Mayen, an isolated North Atlantic island (71°N, 8°30′W), using a Burkard seven-day volumetric trap from 24th April to 31th August, 1988, revealed only very small concentrations. A total of 10 different pollen types were recorded, constituting a seasonal sum of 29 pollen grains. The local pollen season was confined to July, with Oxyria digna and Salix as the most numerous pollen types recorded. Exotic pollen grains, namely Betula, Pinus and Castanea type, were recorded in three periods during June and July. Studies of back trajectories indicate North America and/or Iceland and Greenland as possible source areas for the Betula pollen. There were more diatoms than pollen in the local airspora. Fungal spores mainly occurred in late July and August. Cladosporium constituted less than 5% of the total seasonal sum of fungal spores, while basidiospores contributed nearly 12%. The highest diurnal average of Cladosporium was 27 spores m^?3 air. The seasonal maximum of unidentified fungal spores reached a diurnal average of 639 spores m^?1 air on 27th August.     

A comparison of Betula pollen seasons at two European sites; Derby, United Kingdom and Poznan, Poland (1995–1999).

A comparison of Betula pollen, animportant European aeroallergen, was undertakenat two sites of similar latitude, Derby, UnitedKingdom and Poznan, Poland from 1995–1999. Bothsites routinely monitor Betula pollenusing a Burkard continuous volumetric sampler.Daily and two-hourly March–June Betulapollen counts per cubic metre of air werestudied at both sites, together withcorresponding meteorological data. Detailedanalysis was undertaken to compare start dates,duration and quantity of Betula pollen.Derby usually had an earlier start of seasonthan Poznan, and both cities showed very littledifference between start dates determined byusing the SUM 75 or 2.5% method. The longestseasonal durations at Derby and Poznan yieldedthe lowest seasonal pollen indexes. Every yearfrom 1995–1999 the Betula seasonal pollenindex was higher in Poznan than in Derby. Poznanhad more daily counts of Betula pollengrains per cubic metre above 500, and at leastone daily count of 1000, each year. At bothsites the yearly seasonal variation correlatedwith the number of April days per year having amaximum temperature of 17 °C or above.There was a similar diurnal periodicity ofApril Betula pollen in Derby and Poznan.Although the two cities, at approximately thesame latitude, have different regional andmeteorological characteristics, the weatherappears to influence Betula pollenseasons in a similar manner. Local clinicianscould use the SUM 75 method as indicative ofthe start of the Betula pollen season atboth sites.     

Arctic shrub colonization lagged peak postglacial warmth: Molecular evidence in lake sediment from Arctic Canada

Arctic shrubification is an observable consequence of climate change, already resulting in ecological shifts and global‐scale climate feedbacks including changes in land surface albedo and enhanced evapotranspiration. However, the rate at which shrubs can colonize previously glaciated terrain in a warming world is largely unknown. Reconstructions of past vegetation dynamics in conjunction with climate records can provide critical insights into shrubification rates and controls on plant migration, but paleoenvironmental reconstructions based on pollen may be biased by the influx of exotic pollen to tundra settings. Here, we reconstruct past plant communities using sedimentary ancient DNA (sedaDNA), which has a more local source area than pollen. We additionally reconstruct past temperature variability using bacterial cell membrane lipids (branched glycerol dialkyl glycerol tetraethers) and an aquatic productivity indicator (biogenic silica) to evaluate the relative timing of postglacial ecological and climate changes at a lake on southern Baffin Island, Arctic Canada. The sedaDNA record tightly constrains the colonization of dwarf birch (Betula, a thermophilous shrub) to 5.9 ± 0.1 ka, ~3 ka after local deglaciation as determined by cosmogenic ¹⁰Be moraine dating and >2 ka later than Betula pollen is recorded in nearby lake sediment. We then assess the paleovegetation history within the context of summer temperature and find that paleotemperatures were highest prior to 6.3 ka, followed by cooling in the centuries preceding Betula establishment. Together, these molecular proxies reveal that Betula colonization lagged peak summer temperatures, suggesting that inefficient dispersal, rather than climate, may have limited Arctic shrub migration in this region. In addition, these data suggest that pollen‐based climate reconstructions from high latitudes, which rely heavily on the presence and abundance of pollen from thermophilous taxa like Betula, can be compromised by both exotic pollen fluxes and vegetation migration lags.     

Alnus andBetula pollen content in the atmosphere of santiago de Compostela, North-Western Spain (1993–1995)

The present study analyzes the behaviour ofAlnus andBetula pollen in the atmosphere of the town of Santiago de Compostela (N.W. Spain) from January 1993 to December 1995. The main pollination period of both taxa is identified for each sampling year, which, in the case ofAlnus, took place in January and February and, forBetula, during April.Alnus andBetula pollen are found in very high quantities in the atmosphere of Santiago de Compostela, representing 5% and 12% respectively of the total annual pollen that was counted. We studied the correlation between pollen content each year for both taxa and the main meterological parameters (average, maximum and minimum temperatures, precipitation and hours of sunshine). Finally, we analyzed the diurnal behaviour model for each taxon. ForAlnus, the maximum concentrations were found around 20:00 h, while, in the case ofBetula, the main pollen concentration took place between 15:00 h and 20:00 h in 1993 and 1994, and at 00:00 h in 1995.     

Allergenic airborne pollen monitoring of Vigo (NW Spain) in 1995–2001

Pollen data from the atmosphere of Vigo, NW Spain was collected using a Hirst type pollen trap over a seven-year period (1995–2001). A total of 56 different pollen types were identified, among which Urticaceae, Poaceae, Betula and Quercus represent the greatest risk for people suffering from allergic rhinitis (hay fever) or other allergic diseases. Although in the atmosphere of Vigo the presence of allergenic pollen is constant throughout the year, the months of March and April account for 40% of the annual total pollen count. Two main risk periods have been identified for asthma and allergies: (1) March – April, and (2) June – July, the latter is of greater importance due to high concentrations of Poaceae pollen. Correlation analysis with meteorological parameters demonstrates that rainfall, relative humidity, maximum temperature, sun hours and north-easterly winds are the main factors influencing the average daily pollen concentrations in the atmosphere.     

Pollen concentrations inside private cars during the Poaceae and Artemisia spp. pollen season – a case study

A growing number of studies are researching indoor air concentrations of pollen in buildings, but to our knowledge no studies have dealt with the precise concentration of pollen inside private cars. The aim of this study was to assess the risk of exposure to pollen in private cars throughout the Poaceae and Artemisia spp. pollen season.

The study was conducted in the town of Lappeenranta and along Highway 6 in south‐east Finland between July 14 and August 17, 2003. The pollen concentrations were measured inside two moving and parked cars using rotorod‐type samplers. Surface and ambient Burkard samples were also collected.

Both Poaceae and Artemisia spp. pollen were recorded only on one day and in low concentrations (<10 pollen grains per cubic meter, pg/m³) inside moving and parked cars, whereas the concentrations of Betula spp. (0–15 vs. 0–12?pg/m³) and Pinus (0–41 vs. 0–80?pg/m³) ranged from low to moderate, respectively. The number of pollen grains on the inside surfaces of cars ranged from zero to 72?pg/cm² during the measurement periods.

The concentrations of Poaceae and Artemisia spp. pollen in the indoor air of the car during the flowering period were low, therefore, likely to cause reactions only in the most sensitive people. By contrast, even after the main flowering period the concentrations of Betula spp. pollen were on a level high enough to cause reactions in individuals with allergies.     

<Emphasis Type="BoldItalic">Betula</Emphasis> spp. pollen in the atmosphere of Novi Sad (2000–2002)

Pollen of Betula spp. is one of the main European aeroallergens. The aim of this study was to determine characteristics and occurrence of the Betula pollen in Novi Sad atmosphere, based on 3-year observations (2000–2002), and to compare pollen season start dates calculated by different methods. Pollen samples have been collected by Hirst volumetric method with a 7-day Burkard spore trap. Four methods (Sum 75, 2.5%, 30 and 1 pg/m ³) have been used for determination of the start dates of the Betula pollen season and the results have been compared. The total annual pollen sum increased during the observed period. In 2000, 2001 and 2002, the highest daily pollen concentrations were 97, 137 and 1034 pg/m ³, respectively. The earliest Betula pollen season start has been calculated by the 1 pg/m ³ method.     

UK regional variations in Betula pollen (1993–1997)

Betula pollen is known to be an importantaeroallergen in Europe and the UK, with very largequantities of pollen released into the air at theheight of the season, making it the most abundant treepollen present in the UK spring air.There has been long term pollen monitoring in Cardiff,Derby and London but in recent years the number ofregional sites has increased.Seven sites throughout the UK have monitoredBetula pollen using Burkard samplers for the period1993–1997 and for this study regionaldifferences in Betula pollen and climate wereinvestigated.Detailed analysis revealed considerable variation inthe start dates, duration and quantityof Betula pollen for the seven UK sitesthroughout the five year period.These regional variations in Betula pollenduration and intensity of season, indicate theimportance of maintaining sites throughout the UK asan aid to clinicians, researchers and the generalpublic.     

Fluctuations and trends in airborne concentrations of some abundant pollen types,monitored at Vienna,Leiden, and Brussels

The annual sums of daily airborne pollen concentrations fluctuate from year to year. It has been suggested that for some taxa there is a regular or alternating pattern in these fluctuations. On the other hand, environmental changes may lead to decreasing or increasing trends in airborne pollen concentrations. These two phenomena can only be studied reliably on the basis of long-term volumetric observations of abundantly occurring pollen types. For this study two arboreal (Betula and Quercus) and two herbaceous (Poaceae and Urtica) types were chosen.

For some of these pollen types a weak but significant trend is observed. For the arboreal types (Quercus and Betula) there appears to be a rather constant biennial fluctuating rhythm.     

Pollen influx values measured in different sedimentary environments and their palaeoecological implications

Aspects which need to be considered when calculating pollen influx values in three sedimentary environments (pollen traps, peats and lake sediments) are reviewed. Examples of influx values (grains cm^-2 year^-1) in northern Fennoscandia for two arboreal taxa Betula and Pinus, calculated from these three different environments are presented. Such long term average pollen influx values can be used to indicate the presence/absence and density of the species within the vicinity of the sampling site. Contrary to expectations, conditions do exist in which numerically comparable values are obtained from all three environments. Using these pollen influx values to interpret forest and woodland history in tree-line situations, from both peats and lake sediments, a higher degree of precision can be obtained than through the more classical pollen percentage method alone.     

Characteristics of pollen from natural triploid Betula hybrids

Birch has a key role in the Holocene vegetation history of northern Europe and in sub‐arctic climates dwarf birch and tree birch co‐exist. In Iceland, triploid hybrids between diploid Betula nana (dwarf birch) and tetraploid B. pubescens (downy birch) are common and therefore likely to contribute to pollen deposition. Pollen from 22 triploid trees/shrubs from ten woodlands in Iceland was examined and its size and shape compared with pollen from the parental species. The mean diameter of pollen grains from the triploid hybrids was not statistically different from that of B. nana pollen, but was significantly smaller than the mean value of B. pubescens pollen. On the contrary, the size of the vestibulum was similar to that of B. pubescens, which was significantly greater than that of B. nana, and therefore the diameter‐pore depth ratio was lower than the values from either species. The pattern of size distribution within plants indicated that triploid hybrids might have produced two sizes of triporate pollen grains, but the small B. nana size was far more prevalent than the larger B. pubescens size. Several anomalies in pollen morphology were common among the hybrid pollen grains: four or more pores were the most frequent type of abnormality. Characteristics of the pollen of triploid Betula hybrids, especially structural anomalies, may provide a means to reveal periods of interspecific hybridisation in the analysis of sub‐fossil pollen.     

Substrate dependency of Lateglacial forests in north-east Germany: untangling vegetation patterns, ecological amplitudes and pollen dispersal in the past by downscaling regional pollen

Aim Palynology has revealed that during the Lateglacial Allerød period, Pinus and Betula dominated the forests of north‐east Germany. Because of implicit restrictions, however, palynology fails to reconstruct in detail the distributional patterns and whether monospecific or mixed forests prevailed. Here we test the hypothesis that the distributional patterns of Pinus and Betula were largely determined by substrate. Location Fifteen sites in north‐east Germany. Methods As pollen data reflect the abundance of taxa around a sample site, our hypothesis implies that the abundance of e.g. Pinus pollen should reflect the abundance of substrate types that are favoured by Pinus. (In order to differentiate clearly between taxa and pollen types, the latter are displayed in small capitals. ) We analysed the percentage of Pinus and Betula pollen from an interval in the Allerød, and their relationship to the present‐day proportion of the two dominant substrate types (sand and boulder clay). The substrate proportion was determined in rings from 1 to 50 km around all sites, using four distance‐weighting functions. Results Pollen percentages of Pinus are linearly related to the proportion of sand, and Betula percentages to the proportion of boulder clay. The highest coefficients of determination (r² = 0.89 and 0.91, respectively) were observed for radii of c. 30 km, with distance weighting by 1 and 1/d. Main conclusions The present‐day distributional pattern of substrate types strongly indicates the distributional pattern of Pinus and Betula in north‐east Germany in the Allerød. Assuming that the pattern of substrates remained broadly constant, Pinus dominated on sand and Betula on boulder clay. Our new method thus enables us to refine significantly the reconstruction of habitat characteristics and distributional patterns of taxa in the Lateglacial and Holocene, independent of their present‐day ecological amplitudes. The good performance of the distance‐weighting functions 1 and 1/d indicates that the pollen source area of a site has rather discrete boundaries determined by convective air movements during daytime. Within these boundaries, pollen is evenly distributed over various distances. This implies that light pollen types are transported further than predicted by Sutton’s equation on particle dispersal.     

Artificial neural network model of the relationship between <Emphasis Type="Italic">Betula</Emphasis> pollen and meteorological factors in Szczecin (Poland)

Birch pollen is one of the main causes of allergy during spring and early summer in northern and central Europe. The aim of this study was to create a forecast model that can accurately predict daily average concentrations of Betula sp. pollen grains in the atmosphere of Szczecin, Poland. In order to achieve this, a novel data analysis technique—artificial neural networks (ANN)—was used. Sampling was carried out using a volumetric spore trap of the Hirst design in Szczecin during 2003–2009. Spearman’s rank correlation analysis revealed that humidity had a strong negative correlation with Betula pollen concentrations. Significant positive correlations were observed for maximum temperature, average temperature, minimum temperature and precipitation. The ANN resulted in multilayer perceptrons 366 8: 2928-7-1:1, time series prediction was of quite high accuracy (SD Ratio between 0.3 and 0.5, R > 0.85). Direct comparison of the observed and calculated values confirmed good performance of the model and its ability to recreate most of the variation.     

Airborne pollen concentration in Ankara,Turkey 1990–1993

Atmospheric pollen was collected with a Burkard spore trap in Ankara, Turkey, from January 1990 to January 1993. A total of 135.787 grains/m³ belonging to 47 taxa were observed. The local pollen season started in February in 1990 and 1991 and in March in 1992. Relatively low pollen concentrations were recorded in 1990 and 1992, probably because of precipitation and low wind speed in the spring. A relatively high pollen concentration was recorded in 1991 which could be caused by higher wind speed in the spring and more precipitation during the winter. Cupressaceae/Taxaceae, Pinaceae, Gramineae, Betula, Moraceae, Platanus, Populus, Acer, Quercus, Chenopodiaceae/Amaranthaceae, Plantago, Rumex are found to be the dominant pollen types in the atmosphere in Ankara. The pollen composition generally reflects the vegetation of gardens, parks and roadsides, while the natural steppe vegetation of the area around Ankara is not properly represented.