Pollen Catch Research Articles

Aerobiological Pollen Deposition and Transport of Fraxinus excelsior L. at a Small Spatial Scale

The ongoing fragmentation of ash populations due to ash dieback requires an effective gene flow between individuals; thus, investigations on ash pollen transport are essential. In this study, comprehensive aerobiological field experiments at two seed plantations in Baden-Württemberg were conducted in 2019 and 2020 in order to study the influence of phenology and meteorology (especially wind) on pollen transport using self-constructed gravimetric pollen traps located 1.5 and 5 m a.g.l. Our main objectives were to investigate the local scale dispersion of ash pollen and to evaluate the recommended distance (i.e., 400 m) from seed plantations to other ash trees according to the German Forest Reproduction Act. Our results showed a link between pollen transport and meteorology, the onset of phenological development, and the topography of the plantation. The plantation at Schorndorf was characterized by a slope and associated cold air flows, suggesting that this could be a factor contributing to higher pollen levels at the downslope traps. In addition, in many cases, the cardinal direction associated with the highest pollen impaction was also identical with the predominant wind direction. Analyzing pollen data for single traps in detail, we found that the highest total pollen catch (31%) was measured outside the plantations in 2019, a year with very low flower development. In contrast, most pollen (33%) was caught within the plantation in 2020, which presented a much stronger pollen year than 2019 (with a factor of 11 regarding total sums). This indicates, in the lower pollen year, a potential higher contribution of trees from outside the plantation, and thus it can be recommended that seed harvesting of ash trees in the plantations should preferentially take place in full mast years. Interestingly, the total pollen deposition in Emmendingen at 5 m height showed little difference compared to the traps at 1.5 m height, but there was a large temporal difference pointing to vertical variations in pollen availability. In general, we found that ash pollen was transported for a larger distance than 400 m, but the amount of pollen decreased substantially with increasing distance. At a distance of 200 m, there was already approx. 50% less pollen captured from the air. However, even at a distance of 500 m, more than 10% of the pollen was still captured. In order to ensure cross-pollination of healthy ash trees, the distance of ash individuals or stands should not be too large, and there should be no spatial separation (e.g., by conifer stands).

Using long-term data to reveal the geographical variation in timing and quantity of pollen and seed production in silver and pubescent birch in Finland: Implications for gene flow, hybridization and responses to climate warming

Silver (Betula pendula) and pubescent birch (B. pubescens) are the two main broad-leaved tree species in boreal forests and Subarctic areas, with great significance for both northern societies and ecosystems. Silver birch has more economical importance as it grows taller, but pubescent birch reaches much further North. The adaptability and genetic diversity of Subarctic birch populations are assumed to derive from inter- and intraspecific hybridization. Southern pollen clouds could in turn increase the adaptability of northern populations to warming climate. In the boreal forest zone of warmer climate, incompatibility reactions may prevent interspecific hybridization and much depends on the synchrony of flowering. Direct in situ observations are, however, mostly lacking and earlier results concerning the spatial and temporal match of flowering phenology between the species are contradictory. Conclusions based on pollen catches may also be biased as the pollen of silver and pubescent birch are notoriously difficult to sort out and the geographical origin of pollen is virtually impossible to determine. Here we employ direct flowering observations and reanalyze old pollen and seed production data, collected along a South-North gradient in Finland, to shed more light on these issues. Our results suggest that interspecific hybridization is an unlikely mechanism of adaptation in silver and pubescent birch as there is no significant overlap in flowering either near Subarctic or in more southern boreal areas (covering latitudes 60– 68° N). Long-distance southern gene flow also unlikely has importance in the adaptation of northern populations to a warming climate as heat sum requirements for flowering in northern and southern populations are equal and northern birches are therefore not receptive at the time of southern flowering. Long-term data of pollen and seed production in turn suggest that pubescent birch is more effective in seed production through the whole South-North gradient, but increasingly so towards the North. However, it appears that this difference is not due to silver birch flowering and regeneration being more sensitive to interannual variation as earlier suggested. Although there are more factors than reproduction alone that can affect species distributions, these two findings indicate that climate warming may not significantly alter the relative abundances of silver and pubescent birch in Subarctic Fennoscandia.

Prevalence of airborne allergenic Amaranthus viridis pollen in seven different regions of Saudi Arabia

BACKGROUNDAmaranthus pollen grains are known to be highly allergenic and a potential cause of respiratory allergic diseases. Nevertheless, data on the prevalence of Amaranthus pollen in the environment is limited and almost non-existent for Saudi Arabia.METHODSWe conducted an investigation to record the airborne incidence of A. viridis and other allergenic pollen in Al-Khobar, Dammam, Hail, Jeddah, Jizan, Qassim and Taif, using Burkard Volumetric Samplers. The samplers were operated continuously for one year at each location.RESULTSThe data revealed A. viridis as one of the major components of outdoor airspora, constituting a maximum of 96% of total pollen counts in Hail, followed by Al-Khobar (89%), Jeddah (87%), Qassim (85%), Taif (84%), Dammam (83%) and Jizan (61%). These higher percentages contributed largely to the total weed pollen catch during August to November in all seven regions. In addition, the data also showed that A. viridis pollen were present throughout the year with distinct seasonal variations. The diel periodicities for at least five sites averaged over a year showed mid-day to early evening maxima. The maximum concentration approached 3000/m3 of air in October and 1827/m3 of air in September. The data also exhibited a seasonal pattern in their maximum appearance.CONCLUSIONFurther studies related to biochemical and allergological aspects are needed to confirm the allergenic impact of Amaranthus pollen and sensitization in allergic individuals in the Kingdom of Saudi Arabia.

Integration of flowering dates in phenology and pollen counts in aerobiology: analysis of their spatial and temporal coherence in Germany (1992–1999)

We studied the possibility of integrating flowering dates in phenology and pollen counts in aerobiology in Germany. Data were analyzed for three pollen types (Betula, Poaceae, Artemisia) at 51 stations with pollen traps, and corresponding phenological flowering dates for 400 adjacent stations (< 25 km) for the years 1992-1993 and 1997-1999. The spatial and temporal coherence of these data sets was investigated by comparing start and peak of the pollen season with local minima and means of plant flowering. Our study revealed that start of birch pollen season occurred on average 5.7 days earlier than local birch flowering. For mugwort and grass, the pollen season started on average after local flowering was observed; mugwort pollen was found 4.8 days later and grass pollen season started almost on the same day (0.6 days later) as local flowering. Whereas the peak of the birch pollen season coincided with the mean flowering dates (0.4 days later), the pollen peaks of the other two species took place much later. On average, the peak of mugwort pollen occurred 15.4 days later than mean local flowering, the peak of grass pollen catches followed 22.6 days after local flowering. The study revealed a great temporal divergence between pollen and flowering dates with an irregular spatial pattern across Germany. Not all pollen catches could be explained by local vegetation flowering. Possible reasons include long-distance transport, pollen contributions of other than phenologically observed species and methodological constraints. The results suggest that further research is needed before using flowering dates in phenology to extrapolate pollen counts.

An analysis of the possible effects of the 2001 foot and mouth disease epidemic on grass pollen concentrations in the Midlands, UK

The 2001 grass pollen season in the United Kingdom was notably severe. An epidemic of foot and mouth disease (FMD) occurred in the UK during February and spread through the country during the summer. The media claimed that the control measures of culling infected animals and the restricted movement of stock, led to reduced grazing allowing pastures to flower more than in previous years. This study aimed to examine whether the severity was due only to weather factors or if the control measures also contributed. Three pollen sites from the FMD-affected Midlands region were investigated and compared with two sites from regions unaffected for differences in pollen catches, culling levels and weather. The June pollen catch in the Midlands was particularly high but this pattern also features in areas such as Cambridge in the East that were minimally affected by the epidemic. In most of the catchment areas affected by FMD the quantity of animals culled was less than 10% of the total livestock. In areas where culling was concentrated we can assume that there would have been some localized affect on the pollen levels. The results show that the main influencing variable on the 2001 grass pollen counts in the Midlands was the weather and that culling due to the foot and mouth epidemic did not exert an important influence at the regional level.

Reproductive phenology in a Norway spruce seed orchard

Reproductive phenology was studied in a Norway spruce seed orchard, located in southern Finland (62°13’N, 25°24’E), consisting of 67 clones from northern Finland (64°–67°N). Timing of flowering was determined on the basis of data recorded by a pollen catch meter during 1984–1995, and visual observations made on grafts in 1989, 1992, 1993 and 1995. The genetic and environmental factors affecting female and male phenology, and reproductive synchronisation were studied. The between-year variation in the timing of flowering was more than three weeks. However, when it was defined on the basis of the effective temperature sum, the variation was smaller. No phenological reproductive isolation was found between the seed orchard and surrounding natural forests. The duration of the receptive period of the seed orchard varied from 5 to 8 days, and anthesis determined on the basis of airborne pollen from 5 to 10 days. The receptive period started about one day earlier than anthesis, except in one abnormally warm flowering period when female and male flowering started simultaneously. In general, the flowering periods of the different clones overlapped. The clonal differences in the phenology of receptivity were in most cases statistically significant, but in pollen shedding they were not. The broad-sense heritability estimates were higher for female than for male phenology. Environmental factors, conversely, had a stronger effect on male phenology. A wide graft spacing and a graft position that favoured solar radiation on the lower parts of the crown promoted early pollen shedding and, subsequently, better reproductive synchronisation between female and male flowering.

Pollen input to, and incorporation in, two crater lakes in tropical northeast Australia

Pollen input to the water surfaces of maar crater lakes Barrine and Eacham (1 km 2 and 0.5 km 2 respectively, ca. 720 m a.s.l.), surrounded by rainforest in northeastern Australia, were measured in floating Tauber traps for a variety of periods spanning the years 1978 to 1985. The mean weekly total pollen catch is 75% of that estimated for the surrounding region of varied vegetation. Regardless of their sources, the influxes of pollen taxa are unevenly distributed over the lakes' surfaces. There is similar variation through time, with some indication that this might be smoothed over periods of 5 years or more. There are no inflow streams and pollen input down surrounding slopes is negligible. Mean total pollen influx to seston traps close to the lakes' bottoms (1979 to 1988) is <5% of that to the Tauber traps, a discrepancy attributed to trap design. In contrast, mean annual influx measured by the Tauber traps is similar to that estimated from dated sediment samples younger than 1966 AD at Lake Barrine. The proportions of different pollen taxa are less affected by trap position or period of exposure than are their influxes; their mean percentages for Tauber traps, seston traps and sediment samples are all rather similar. The similarity between the mean contribution of exclusively rainforest pollen to the lakes' surfaces (56%) and to Oldfield traps in rainforest interiors (51%) emphasizes the importance of the rainforests, which clothe the crater walls, as sources of pollen to the lakes. The impact of pollen from other vegetation in the region, although present, is much smaller than at interfaces between rainforest and other vegetation types. All this pollen is mixed within and above the crater and delivered to the lakes' surfaces by gravity and frequent rainfall. Limnological processes redistribute it in the water body before it is incorporated into the deep-lake sediments. The value and limitations of current pollen transport and accumulation theory are noted in relation to sites with morphologies similar to these two crater lakes and to the irregular flowering and floristic inhomogeneity of tropical rainforest. The potential for the use of modern pollen input data in the interpretation of pollen analyses from the sediments of such sites is explored.

Aeroallergens of plant origin: Molecular basis and aerobiological significance

This review presents an update on the sources and molecular basis of aeroallergens of plants, derived from pollen, seeds, leaf and stem detritus and their protein molecules. These aeroallergens are a natural component of the atmosphere, either because of their natural function or human activity. Pollen is a source of allergens within the 10–200 μm size range, and while most allergenic pollen types account for only 20–30% of total annual pollen catch, during their flowering season, they are usually the dominant type. Tree pollen commences the season in winter, with birch pollen counts in Scandinavia being the highest daily pollen counts yet reported and a major allergen, a 14-kDa protein, which is similar to pathogenesis-related proteins. Grass pollen follows in spring, and is unique as its two immunodominant allergens, a 35-kDa glycoprotein and 28–32-kDa protein, are in different cellular sites: the cytosol and surface of pollen grains; and in intracellular starch granules. The allergens at the pollen surface are not inhalable and can interact only with the eyes, nasal and oral cavities. Starch granules are released to the atmospheric aerosol when grains rupture in rainwater. These are a major source of allergen-containing micronic particles, which are important because they are inhalable. At the same time, allergen molecules are present in the aerosol, and these can bind to soot particles, and so be respired deep into the airways. The major Japanese cedar pollen allergen has been detected both within the pollen and in orbicules; particles less than 1 μm that line the anther cavity and can be released into the air when dehiscence occurs. Ragweed is the major cause of late summer hayfever in eastern North America, where its pollen accounts for up to 41% of the annual pollen catch. It is a major source of aeroallergens in both respirable and non-respirable size ranges. As a result of human activity, dusts derived from seeds and cereal grains during transport, storage and milling provide a source of micronic particles, containing potent allergens that can trigger allergic disease.

Pollen and Mould Allergy in Southern Sardinia (Italy): Comparison of Skin-Test Frequencies and Air Sampling Data

Abstract A study was carried out to investigate the influence of atmospheric pollen and fungi in determining allergic diseases by comparing the frequency of skin reactions to air sampling data over a 6-year period. 48% of our population reacted to at least one of the pollen and fungal extracts used. Among pollen, Gramineae gave the most frequent positive reactions, followed by Parietaria, Olea and Compositae. The most common positive skin tests in fungus sensitive patients were by extracts of Alternaria, Cladosporium, Aspergillus and Candida As for the aerobiological survey, the general trend of pollen and molds was similar during the sampling period. The annual pollen catch did not show remarkable differences during the years sampled, whereas the total fungal spore count was highest in 1988 and 1990. A comparison between aerobiological and clinical data revealed a good degree of concordance between total pollen counts and positive skin test frequencies for Urticaceae, Gramineae and Oleaceae but not for C...

Pollen Contamination Evaluation on a Proposed Eastern Larch Seed Orchard Site

Abstract Pollen monitoring was conducted in 1988 and 1989 in an open field in Ste. Anne de Madawaska (N.B., Canada) proposed for the establishment of an eastern larch clonal seed orchard. Eastern larch is a common species in the area, and a stand is located adjacent to the study site. The objective of the study was to evaluate the level of pollen originating from the adjacent stand and from more distant stands. Pollen traps were established along a transect downwind to the stand and monitored daily. Pollen catch in 1989 was 2.7 times less than in 1988. Pollen catch downwind from the stand was described according to three phases. Early in the study, pollen catch originated only from the stands; then, increased numbers of pollen originated from other sources; finally, pollen catch was only from other sources. Pollen from the stand represented about 5-10% of larch pollen catch in both 1988 and 1989, and the remaining originated from more distant sources. Removal of the stand would have had little impact on total pollen influx on to the proposed orchard site. North. J. Appl. For. 11(4):124-130.

Seasonal Variation in Pollen Catch in a Black Spruce Orchard

Abstract Pollen monitoring was conducted over three years (1987–1989) in a 12.4 ha Picea mariana (Mill.) B.S.P. (black spruce) seedling seed orchard established from 1979 to 1984. Pollen traps were installed around and within the orchard and collected daily. Pollen-cone production was highest in 1988 with an average of 0, 11, 20, and 38 cones per tree for 5-, 8-, 9-, and 10-year-old trees. Trees of the oldest section of the orchard bore about 60% of the total number of orchard pollen cones in 1987 and 1988 but only 26% in 1989. Pollen contamination during seed-cone receptivity was important in all three years assessed. The increase in pollen contamination from 1988 to 1989 resulted, in part, from 1) the roguing of 63% of trees in the oldest section of the orchard and 2) a 17-fold decrease in orchard pollen production from 1988 to 1989 compared to a 5-fold decrease from contamination sources.

Changing grassland utilization in the united kingdom and its implications for pollen production and hay fever

Abstract Grasses form the most important source of airborne pollen in the United Kingdom. This article reviews the ecological, geographical and historical features of grassland utilization relevant to pollen production. During the past half century extensive agricultural management, with botanically diverse swards and late (post anthesis) mowing for hay, has been progressively replaced by more intensive management with more reliance on Lolium perenne and early mowing for silage. The role of Dactylis glomerata and Phleum pratense has declined. A decrease in the June pollen catch supports the hypothesis that these changes have affected the quantities of pollen released. Incidence of hay fever shows geographical variation with climate, topography and vegetation type. Recent policy changes intended to decrease agricultural production and to meet environmental objectives may, in future, further affect the types and quantities of pollen produced.

Comparison of airborne pollen grains in Huddinge and Stockholm, Sweden

Airborne pollen studies were carried out, by means of Burkard volumetric spore traps, at two different sites (the city of Stockholm and the suburb Huddinge) 15 km apart in the Stockholm region. Within the city of Stockholm the study was carried out in 1973–89 while in Huddinge the investigation period was 1977–82. In all the years under investigation the total pollen catch and the number of pollen types were higher in Stockholm than in Huddinge. The reason for this is not explained by the composition of the local vegetation surrounding the traps. It is concluded that parameters such as qualitative changes in the daily catches and occurrence during the main pollen season are more important than the absolute daily figures. The cyclic trends in the local annual sums over a long period of years do not show any periodicity that is altogether regular and reliable.

Pollen contamination in a small black spruce seedling seed orchard for 3 consecutive years

Pollen monitoring was conducted in 1987, 1988, and 1989 in the 2.8 ha Second Falls black spruce ( Picea mariana (Mill.) B.S.P.) seedling seed orchard established in 1978. The objectives of the study were to evaluate (i) the orchard pollen-cone production, (ii) the level of orchard pollen production, and (iii) the level of pollen contamination for 3 consecutive years. Pollen traps were established around the orchard and collected on a daily basis. Pollen-cone production per tree averaged 3, 40, and 76 in 1987–1989, respectively. Pollen contamination during seed-cone receptivity was estimated to be 32%, 83%, and 58% in 1987, 1988 and 1989, respectively. The important increase in pollen contamination from 1987 to 1988 resulted, in part, from (i) the roguing of 40% of orchard trees and (ii) a 37-fold increase in pollen catch from contaminant sources from 1987 to 1988 compared to a 3.6-fold increase in pollen production by orchard trees. Supplemental mass pollination and synchronization of high orchard seed-cone and pollen-cone production with low pollen production from contaminant sources are suggested to reduce the level of pollen contamination, to increase panmixis and seed yield, and to maximize genetic gain.

Airborne Pollen of Toulouse, Southern France

Abstract Three consecutive years of pollen sampling using the Cour's filter technique (1974) revealed the incidence and phenological details of atmospheric pollen in Toulouse including percentage of pollen grains causing allergic symptoms. The pollen catch at three stations in southern France is compared. In Montpellier the pollen season begins earlier with larger amount of pollen. In each spectrum, some taxa (Pinus, Alnus, Ericaceae, Betula, Salix, at Bordeaux; Gramineae, Quercus, Ulmus, at Toulouse; Fraxinus, Chenopodiaceae-Amaranthaceae, Plantago, Artemisia, Urticaceae, Olea at Montpellier) appear to be characteristic of the regional vegetation which is linked to the ecological parameters.

Long range transport ofCastanea sativapollen

Abstract In the course of an aerppalynological study, during 1983 to 1985 in Samedan (High-Engadin), large amounts of Castanea pollen were found in the samples. These amounts vary between 6.3% and 14.5% of the annual total pollen catch. The altitude of Samedan is 1705 m above sea level. The nearest important Castanea forests are situated quite far away in the Southern Alps, and always at altitudes below 1000 m. At Samedan more than 61 % of the Castanea pollen are caught during the night with a maximum count at midnight. These observations indicate strongly that Castanea pollen is carried by the “Maloja-Wind” from the extensive Castanea forests of the Bergell valley to the High-Engadin.

Comparison of pollen data from Tauber traps paired in the field with simple cylindrical collectors

Abstract Pollen rainsplashed from the collar of the Tauber trap could augment significantly the catch due to direct deposition. To test for rainsplash error under natural conditions, Tauber traps were paired in the field with simple jar traps without collars. Relative pollen catches during dry weather would have established a performance ratio between these types of trap (attributable solely to differences in their aerodynamic efficiency) but rain during all sampling periods unfortunately precluded this comparison. The average pollen catch per sampling period was consistently higher in the Tauber trap than in the jar trap, despite variations in weather. However, differences in pollen catch between the two traps in a pair were always lowest under trees where, paradoxically, maximum rainsplash error was expected (but where wind speeds were low), and highest in the centre of a lake (where wind speeds were higher). These results suggest that higher pollen catches in the Tauber trap than in the jar trap were d...

Comparison of air-borne pollen at Louvain-la-Neuve (Belgium) and Basel (Switzerland) during 1979 and 1980

Abstract The pollen production for both years was three times higher in Basel than at Louvain-la-Neuve. The interpretation of the pollen calendars showed an average onset of eight days earlier in 1979 and five days earlier in 1980 for the taxa in Basel. The pollen catch for both stations was greater in 1980 than in 1979, which was characterized by an average delay in the onset of pollen shedding both in Basel and at Louvain-la-Neuve.

Studies on pollen allergy in Delhi. Diurnal periodicity of common allergenic pollen.

The volumetric sampling of the air has been carried out with the Suction Impaction Sampler devised by Tilak & Kulkarni (1970). The pollen counts have been expressed as number per cubic metre volume of the air. Based on the percentage of pollen peaks, diurnal patterns of the total count of all the types, and six dominant allergens have been determined. For these allergens, daily fluctuations have also been recorded. The influence of meteorological factors such as temperature, wind, rainfall, relative humidity and sunshine hours/day on the variation patterns in the concentration of atmospheric pollen has been discussed. It has been shown that 25-30 degrees C temperature, 5-15 km/h wind speed, 60-70% RH, bright sunny and rain-free days are favourable for high pollen catch. These weather conditions might be conducive for the high discharge, dispersal, and deposition of air-borne pollen. Too low or too high temperature, very high wind speed, high humidity, and cloudy and rainy days hinder high pollen catch.

Effect of wind-borne pollens on the population dynamics ofAmblyseius hibisci [Acarina: Phytoseiidae

Populations ofAmblyseius hibisci (Chant), an important predator of citrus red mite,Panonychus citri (McGregor) exhibited varying responses to field applications of cat-tail,Typha latifolia L., pollen in San Joaquin Valley citrus groves. Predator densities increased to significantly higher levels after pollen treatments during the fall months, and to a limited extent after late winter treatments, but not after early spring treatments. The amount of response appeared to be inversely related to the levels of natural foods present during the various seasons. Results of the wind-borne pollen monitoring studies indicated that population growth inA. hibisci was correlated with the seasonal pattern of pollen fallout. Population growth was slowest in years when pollen catches were low during the late winter and early spring, and fastest in years when peak pollen catches occurred in late winter or early spring. Population growth inA. hibisci did not appear to be markedly responsive toP. citri populations although suppression of prey densities was indicated in ca. 50% of the cases. In laboratory tests,A. hibisci reproduced through 3 generations on 11 of 23 pollens tested.