The effects of climate change on the birch pollen season in Denmark

During the last two decades the climate inDenmark has become warmer and in climatescenarios (IPCC, 2001) it is foreseen that thetemperature will increase in the comingdecades. This predicted future increase intemperature will probably affect both theflowering of plants and the dispersion ofpollen in the air. In this study the alreadyobserved effects on the birch pollen season arestudied.Trend analyses of the birch pollen seasonfor two stations in Denmark more than 200 kmapart give similar results. In Copenhagen thereis a marked shift to an earlier season – itstarts about 14 days earlier in year 2000 thanin 1977, the peak-date is 17 days earlier andthe season-end is 9 days earlier. For Viborgthe trend to an earlier season is in generalthe same, but slightly smaller.During the same period there has also beena distinct rise in the annual-total amount ofbirch pollen, peak-values and days withconcentrations above zero.Rising mean temperatures during winter andspring can explain the calculated trends towardearlier pollen season. Models for estimation ofthe starting date based on Growing Degree Hours(GDH's) give very fine results with acorrelation coefficient around 0.90 and rmserror around 4.2 days.For annual-total there is a significantpositive correlation with the mean temperaturein the growing season the previous year.     

The influence of air temperature on the starting dates of the pollen season of alnus and populus

In this work we have studied the influence of air temperature on the starting dates of Alnus and Populus pollination in two different climatic regions in Europe: central Italy and The Netherlands. The start of the Alnus pollen season varied between 27th January and 16th February in the Italian stations while in The Netherlands it showed an average delay of about one month. For Populus the beginning of the pollen season was delayed on an average 15 days at Dutch places compared to central Italy. In the former it varied between 14th March and 21st April while in the latter between 28th February and 24th March. Significant correlations exist between the beginning of pollination for these taxa and temperature conditions in the preceding periods. The highest correlations found were with daily mean decade temperature for three decades before the average starting dates of the pollen season. These correlations were better for The Netherlands than for central Italy perhaps because the temperature in Holland is the more prominent meteorological factor (relative to precipitation) compared with central Italy, where precipitation has much influence in winter. This study indicated correlations between the pollination and temperature also during the dormant period in the preceding season.     

Time linkages between pollination onsets of different taxa over an 11-year period in Perugia,Central Italy

Times of pollination of different taxa in the atmosphere of Perugia (Central Italy) over an 11-year period (1982–1992) were recorded and analysed by means of a 7-day volumetric Hirst-type pollen trap. For some taxa, the pollination period varied from year to year from a chronological and/or quantitative point of view. Several taxa showed a linkage in their starting dates of pollination. Knowledge of this kind of linkage allows us to build a forecasting model.     

Variations and trends of birch pollen seasons during 15 years (1996–2010) in relation to weather conditions in Poznań (western Poland)

Birch (Betula) pollen seasons were examined in relation to meteorological conditions in Poznań (1996–2010). Birch pollen grains were collected using a volumetric spore trap. An alternate biennial cycle of birch pollen season intensity was noticed in Poznań. The main factors influencing birch pollen season intensity were average daily minimum temperatures during the second fortnight of May and the month of June one year before pollination as well as the intensity of the pollen season of the previous year. Most of the pollen grains are recorded during the first week of the season; the number of pollen grains recorded at this time is positively correlated with mean maximum temperature and negatively correlated with daily rainfall. The significant effect of rainfall in reducing the season pollen index was noticed only during weak pollen seasons (season pollen index <?mean). In addition, mean daily maximum temperature during the first two weeks of the birch pollen season markedly influences its duration. No significant trends in duration and intensity of the pollen season were recorded, however, a slight tendency towards early pollination was observed (?0.4 days/year, p?=?0.310).     

Airborne pollen data of Platanaceae in Santiago de Compostela (Iberian Peninsula)

The pollen count of the Platanus genus in the atmosphere of Santiago de Compostela (Galicia, Spain) was carried out from 1993 to 1998, with the pollen of this taxon representing 6% of total identified pollen. The principal pollination period (P.P.P.) was centred on the months of March and April, with an average duration of 23 days.During the study period we obtained negative correlations with precipitation and humidity and positive ones with temperature and hours of sunshine, with a confidence index of more than 90%. On the basis of the six-year study period, we also calculated the average accumulated temperature required to trigger the onset of flowering, which oscillated between 330 and 456 °C, with this result being confirmed for 1999 (437 °C). We also observed that the values of maximum pollen concentration of this taxon in the last 7 years (1993–1999), were obtained on days during the P.P.P. with maximum temperatures above 18 °C. The model of intradiurnal variation reflects, for the majority of years, a greater representation during the central hours of the day.     

Correlation between meteorological conditions and Parietaria pollen concentration in Alassio,north-west Italy

The pollen grains in the atmosphere in different geographical areas differ according to the species present, the pollination seasons and pollen grain concentrations, but possibly the greatest contributors to this variability are the meteorological conditions. The aim of our research is to establish a possible correlation between Parietaria pollen concentration and meteorological conditions during the period from 1991 to 1995 in the town of Alassio (north–west Italy). As far as vegetation is concerned, the Mediterranean climatic conditions support the blooming of extensive grasslands in the environment surrounding the town; these grasslands mainly comprise Urticaceae and shrubs. The study demonstrates that the most influential parameters affecting the Urticaceae grain concentration upsurge are the absence of rainfall, a maximum daily temperature of about 21 °C, and a diurnal temperature range of about 5 °C. Moreover, our aeropalinological study indicates that this last parameter has the greatest influence on Urticaceae pollination. In fact, an increase in diurnal temperature range could be responsible for a dehydration of pollens resulting in a loss in mass. This grain lightness and volatility would ultimately permit atmospheric dispersion if there is a significant wind speed. On the other hand, days with rain or high relative humidity make pollens heavier, preventing them from flying long distances and therefore partially explaining the decline in airbone pollen concentration.     

Fluctuations of grass pollen content in the atmosphere of East Perugia and meteorological correlations (year 1989)

Summary Gramineae pollination from a pollen monitoring station located in the eastern suburb of Perugia and meteorological correlations are reported. The data refers to the year 1989. Grass pollen peak pollination was from May to July; in this period the influence of relative humidity and of temperature on pollen concentration was very high. Phenological observations, to identify the time of maximum stamen extension in the most common genera in the area, are also reported. During the period of investigation the counts of pollen grains over four-hour periods showed a regular diurnal rhythm with peaks of concentration in the four-hour period 16.00–20.00. Aerosporological data and meteorological data related to four-hour periods were correlated following different criteria.     

The influence of climate changes in Platanus spp. pollination in Spain and Italy

There is evidence of a significant increase in air temperature in the northern hemisphere over recent decades, with consequent changes for anemophilous pollen. In this work we present the effects of climatic change on Platanus spp. pollination in different areas of Italy and Spain, characterized by different climates. In particular, the historical series of pollen monitoring and meteorological data of two Italian stations, Perugia (1982 – 2003) and Torino (1985 – 2003), and two Spanish stations, Santiago de Compostela (1992 – 2003) and Vigo (1994 – 2003), were analysed. The changes recorded in all stations included the timing and behaviour of pollen release. However, no or minimal influence on the total pollen emission was found. Research has linked the changes in phenological events to an increase in temperature, moreover in this study temperature changes are believed to be mainly responsible for the variations recorded in the pollen season of Platanus. A previous start of pollination (?0.66; ?1.21; days/year) is reported in both Italian stations where the temperatures have significantly increased and a delay of 0.2 – 0.8 days/year in Spanish stations where a different trend of temperature is recorded. Other important data is given regarding the type of discharge of pollen grains during the pollen season. Pollination curves are examined by two statistical shape parameters (kurtosis and skewness) which show that pollen release is more gradual with higher temperatures or faster under colder conditions. A regression analysis links the atmospheric pollen presence to mean air temperature.     

Studies on flower longevity in Digitalis

Flower lifespan was terminated by corolla abscission 5–6 days after stigma opening in the unpollinated flower. Increased pollen loads produced increased seed set and reduced flower longevity progressively to a minimum of one day after pollination with pure pollen. Weakening of the abscission zone was detectable 8 h after pollination, whilst the pollen tubes were still within the stigmatic zone, suggesting that a stimulus, moving at 4 mm h^–1 minimum, was transmitted through the style and ovary. Soon after pollination removal of the stigma prevented the pollination-induced corolla abscission. Later it was necessary to remove the stigma and upper style, and later still the whole style to delay abscission. The progressive induction of the stigma and style took place at a rate of 1.5 mm h^–1, in advance of the pollen tubes which grew at 0.75 mm h^–1. It was not possible to reproduce the pollination effects by application of indoleacetic acid (IAA) to the stigma or the style.Abbreviation IAA Indoleacetic acid     

Prediction of the beginning of the olive full pollen season in south-west Spain

Given the clinical and agricultural importance of the olive in SW Spain, we have carried out a study to predict the starting date of its full pollen season. The study covers 6 years of meteorological and palynological observations — the latter using a Cour sampler installed in Huelva (SW Spain). The results obtained show that olive full pollination begins when the plant has accumulated 731°C of daily temperature above 5°C from the end of its dormant period. The mean duration of this accumulation was 83 days. A positive relationship has been found between mean temperature of the months before the pollen season (February and March) and the date when the season starts (April). From the data available, rainfall registered between 1 September and 31 March (both before pollination), does not affect the starting date of the full pollen season, but can affect total pollen production, particularly in years with prolonged drought.     

Prediction of the beginning of the olive full pollen season in south-west Spain

Given the clinical and agricultural importance of the olive in SW Spain, we have carried out a study to predict the starting date of its full pollen season. The study covers 6 years of meteorological and palynological observations — the latter using a Cour sampler installed in Huelva (SW Spain). The results obtained show that olive full pollination begins when the plant has accumulated 731C of daily temperature above 5C from the end of its dormant period. The mean duration of this accumulation was 83 days. A positive relationship has been found between mean temperature of the months before the pollen season (February and March) and the date when the season starts (April). From the data available, rainfall registered between 1 September and 31 March (both before pollination), does not affect the starting date of the full pollen season, but can affect total pollen production, particularly in years with prolonged drought.     

Prediction of the birch pollen season characteristics in Cracow, Poland using an 18-year data series

The aim of the study was to construct the model forecasting the birch pollen season characteristics in Cracow on the basis of an 18-year data series. The study was performed using the volumetric method (Lanzoni/Burkard trap). The 98/95 % method was used to calculate the pollen season. The Spearman’s correlation test was applied to find the relationship between the meteorological parameters and pollen season characteristics. To construct the predictive model, the backward stepwise multiple regression analysis was used including the multi-collinearity of variables. The predictive models best fitted the pollen season start and end, especially models containing two independent variables. The peak concentration value was predicted with the higher prediction error. Also the accuracy of the models predicting the pollen season characteristics in 2009 was higher in comparison with 2010. Both, the multi-variable model and one-variable model for the beginning of the pollen season included air temperature during the last 10 days of February, while the multi-variable model also included humidity at the beginning of April. The models forecasting the end of the pollen season were based on temperature in March–April, while the peak day was predicted using the temperature during the last 10 days of March.     

Differences in atmospheric trees pollen seasons in winter, spring and summer in two European geographic areas, Spain and Italy

The global climate change reported over recent years may prompt changes in the atmospheric pollen season (APS). The aim of this study is to evaluate the possible impact provoked by meteorological conditions variations at different seasons of the year or different geographical areas on APS. Alnus, Betula and Castanea atmospheric pollen seasons and trends during the last 17 years at Ourense and Vigo (Galicia—NW Spain) and Perugia (Italy) were analysed. Possible incidence of the meteorological trends observed in the different cities on the atmospheric pollen seasons and the chill and heat requirements were evaluated. Pollen data from Ourense, Vigo and Perugia (1995–2011) were used. Pollen sampling was performed using LANZONI VPPS 2000 volumetric traps (Hirst in Ann Appl Biol 36:257–265, 1952), placed on top of different buildings at a similar height from the ground. Several methods, dates and threshold temperatures for determining the chill and heat requirements needed to trigger flowering were tested. Different temporary order in the pollination sequence was observed between the three pollen types studied in the three sites. Alnus flowers few days in advance in Ourense respecting to Vigo and 1 month earlier than Perugia. The Betula flowering start date in Ourense and Vigo is almost simultaneous, taking place only 5 days in advance with respect to Perugia. Finally, scarce differences in the APS onset of Castanea were detected between the three cities. The variations observed among the two areas (Umbria, Italy and Galicia, Spain) in the onset of pollen season in the winter or spring flowering trees could be explained by differences in the thermal requirements needed for flowering as consequence of the climatic conditions recorded during the previous period to flowering. The length of the chilling and heat period as well as the thermal requirements obtained showed differences between geographical areas. The chill requirements accumulated were higher in Perugia than Ourense and Vigo. By contrary, the lowest heat accumulation was achieved in Perugia. The observed trends in the APS characteristics and the weather-related parameters were not homogeneous both in the pollen types and sites. The pollen index of Betula and Castanea pollen in Ourense shows a significant trend to increase.     

A study of Quercus pollen in the Derby area, UK

The major allergenic pollen prevalent in the Derby air in May is Quercus pollen which has been monitored volumetrically from 1970–1997. Quercus pollen levels in Derby are increasing, showing an established long term trend, with 1995 being an exceptionally high year. There is now an earlier start date and a longer seasonal duration. The mean Quercus diurnal periodicity for 1991–1997 shows a peak at 15.00 hours.A detailed study of the 1990–1997 seasons established that a maximum temperature of 20 °C or above, at the usual time of flowering, occasions the start of the Quercus pollen season. Average May temperature and drought in the previous June and July are important factors in determining Quercus pollen totals. Predictions for the forthcoming seasons were produced which compared favourably with the actual pollen totals.     

Airborne birch pollen in Neuchâtel (Switzerland): onset, peak and daily patterns

An accurate forecast of the starting point of thebirch pollen season in Neuchâtel can be made byadding the positive daily average air temperature fromFebruary 1st onward until the figure 270 is reached.At this point, the birch trees are ready to bloom.After that, the daily average temperature has toexceed 10 °C to allow pollen release.Today, the birch pollen season starts some 19 daysearlier in the year than in the 1980's, a consequenceof a recent climate change.The daily patterns of airborne birch pollen isirregular. Moreover, pollen concentrations frequentlyexceed the threshold of the appearance of allergicsymptoms, except during rainfall. Therefore, the onlybehavioral recommendation that can be given to peopleallergic to birch pollen is to shorten as much aspossible the contact with outdoor air during the mainbirch pollen season.     

Aeropalynological study of <Emphasis Type="Italic">Vitis vinifera</Emphasis> in the Braga region (1999–2003)

This study shows the results of Vitis vinifera pollen season in the atmosphere of the Braga region (Portugal) for the last 5 years (1999–2003). The fluctuations in the airborne pollen concentration, the synchronic rhythms in the annual pollen trends and their relationship to the main meteorological parameters were investigated. The vineyard pollen season extends from late May to early July, presenting always a bimodal pattern. During the studied period several pollen types such as Poaceae, Castanea, Olea, Urticaceae, Quercus, Plantago, Rumex, Asteraceae, Pinaceae, Ericaceae and Eucalyptus were also observed. Airborne pollen concentration is highly influenced by mean temperature, rain, number of days with rain and wind direction.     

Poaceae pollen in Galicia (N.W. Spain): characterisation and recent trends in atmospheric pollen season

Airborne Poaceae pollen counts are greatly influenced by weather-related parameters, but may also be governed by other factors. Poaceae pollen is responsible for most allergic reactions in the pollen-sensitive population of Galicia (Spain), and it is therefore essential to determine the risk posed by airborne pollen counts. The global climate change recorded over recent years may prompt changes in the atmospheric pollen season (APS). This survey used airborne Poaceae pollen data recorded for four Galician cities since 1993, in order to characterise the APS and note any trends in its onset, length and severity. Pollen sampling was performed using Hirst-type volumetric traps; data were subjected to Spearman’s correlation test and regression models, in order to detect possible correlations between different parameters and trends. The APS was calculated using ten different methods, in order to assess the influence of each on survey results. Finally, trends detected for the major weather-related parameters influencing pollen counts over the study period were compared with those recorded over the last 30 years. All four cities displayed a trend towards lower annual total Poaceae pollen counts, lower peak values and a smaller number of days on which counts exceeded 30, 50 and 100 pollen grains/m³. Moreover, the survey noted a trend towards delayed onset and shorter duration of the APS, although differences were observed depending on the criteria used to define the first and the last day of the APS.     

Annual, daily and intradiurnal variation of Celtis pollen in the city of La Plata, Argentina

The behaviour of Celtis airborne pollenwas studied for a period of three years(1998–2000) in the city of La Plata. The pollengrains were captured with a Lanzoni trap andthe maximum pollination period was observed tooccur during the end of winter and spring inthe three years. The annual values of pollenconcentration varied, and a significantdecrease was observed during 2000. The greatestairborne pollen record was in October with anaverage of 82.3% in relation to its totalconcentration during 1998–2000. Based on theintradiurnal behaviour analysis, it wasobserved that the maximum pollination peakoccurs at 2H when the temperaturereaches its maximum values. Considering thethree sampling years, the meteorologicalvariables that most influenced the processes of pollen emission,dispersion and transportation in the atmospherewere: maximum and minimum temperature andrainfall.     

Seasonal fluctuations of the airborne pollen spectrum in Murcia (SE Spain)

During six consecutive years (1993–1998), aBurkard volumetric pollen trap was continuouslyoperated to sample pollen from the air of thecity of Murcia. The aim of the study was toelucidate the spectra of airborne pollen andthe variations during the year, and toelaborate a pollen calendar. This time spanincludes the end of the period with severedrought from 1990–1995, which particularly affected the south-eastern region of Spain.The total sum of daily average pollenconcentrations amounted to 148,645 pollen grainsbelonging to 93 different taxa. A daily averageof 74 pollen grains/m³ and 11 taxa wererecorded, with maxima of 1157 and 27respectively. The total pollen amountregistered in a year correlated with yearlyrainfall, but there was no relation with meanannual temperature. As for annual fluctuations,there seemed to be no influence by totalrainfall or temperature. Spring and winter werethe seasons with the highest pollen counts andpollen diversity.From the 93 identified taxa, 36 are included inthe pollen calendar. Noteworthy findings are:(i) the presence of Thymelaeaceae,Robinia, Betula, Castanea,Zygophyllum, Caryophyllaceae andCannabis, (ii) a long pollen season ofChenopodiaceae/Amaranthaceae, Urticaceae,Poaceae, Arecaceae and Plantago, (iii)the occurrence of summer, autumn and winterflowering of Artemisia, (iv) the lateappearance of Corylus pollen, and (v) theminor presence of Casuarina pollen duringthe mid winter and late spring.     

Atmospheric Poaceae pollen frequencies and associations with meteorological parameters in Brisbane,Australia: a 5-year record, 1994–1999

Grass pollen is an important risk factor for allergic rhinitis and asthma in Australia and is the most prevalent pollen component of the aerospora of Brisbane, accounting for 71.6% of the annual airborne pollen load. A 5-year (June 1994–May 1999) monitoring program shows the grass pollen season to occur during the summer and autumn months (December–April), however the timing of onset and intensity of the season vary from year to year. During the pollen season, Poaceae counts exceeding 30 grains m^–3 were recorded on 244 days and coincided with maximum temperatures of 28.1 ± 2.0 °C. In this study, statistical associations between atmospheric grass pollen loads and several weather parameters, including maximum temperature, minimum temperature and precipitation, were investigated. Spearmans correlation analysis demonstrated that daily grass pollen counts were positively associated (P < 0.0001) with maximum and minimum temperature during each sampling year. Precipitation, although considered a less important daily factor (P < 0.05), was observed to remove pollen grains from the atmosphere during significant periods of rainfall. This study provides the first insight into the influence of meteorological variables, in particular temperature, on atmospheric Poaceae pollen counts in Brisbane. An awareness of these associations is critical for the prevention and management of allergy and asthma for atopic individuals within this region.