Ambrosia sp. pollen in Switzerland

The presence of Ambrosia sp. pollen is very irregular inSwitzerland. South to the Alps (Ticino), the yearly meanquantities (1993 to 1997) reach 535 pollen grains in Lugano and114 in Locarno. To the West, 205 pollen grains of Ambrosiasp. are observed as yearly mean total in Geneva. In La Chaux-de-Fonds(100 a.s.l.), a yearly mean of 86 pollen is reached, 66 inNeuchâatel, 59 in Payerne and 74 in Basel. In the Swiss RhoneValley, in Visp, this yearly mean reaches 30 pollen ofAmbrosia sp. A little more in the center of the country, inBern, 31 pollen are monitored as yearly mean quantity. In therest of the helvetic territory, in the North and in the East, theyearly mean are below 15 pollen grains. Since 1991–1992, anincrease has been observed essentially in Ticino, in Geneva,Neuchâatel and La Chaux-de-Fonds. The presence of Ambrosiasp. pollen is often noticed in case of strong west or south-westwind flowing, probably coming from the Rhôone Valley and theBresse in France and the Po Valley in Italy.     

<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.     

Differentiating pollen of Betula species from Iceland

Subfossil pollen from two co‐existing Betula species in Iceland, B. nana and B. pubescens, is frequently found in sediments and peat. Interpretation of the findings often depends on the ability to differentiate between the two species according to pollen size and structure. Fresh pollen samples were prepared from 70 individual trees/shrubs which had been identified to species by chromosome number. Grain diameters and pore depths were measured and ratios of grain diameter to pore depth (D/P ratios) were calculated. The mean grain diameters of pollen from diploid B. nana and tetraploid B. pubescens were 20.42 and 24.20?µm, whereas mean pore depths were 2.20 and 2.81?µm respectively. Mean D/P ratios were therefore 9.55 for B. nana and 8.85 for B. pubescens. The difference between species was statistically significant for all three pollen parameters. Grain diameter appeared to be the most useful parameter, as only about 20% of the samples were in the overlapping region of the species distributions. Pollen size (grain diameter) was also positively correlated to tree morphology, which was evaluated using species‐specific botanical characters. Pollen samples from different locations/populations in Iceland varied slightly in mean size and ratio. The size difference between pollen of B. nana and B. pubescens in this study is less than other papers have reported, which may be due to the effect of introgressive hybridisation between the two birch species in Iceland.     

Diurnal patterns of airborne pollen concentration of the selected tree and herb taxa in Gdańsk (northern Poland)

The diurnal variation of airborne pollen concentrations of Alnus, Betula, Pinus, Poaceae, Urtica and Artemisia was examined at the sampling station in Gdańsk, northern Poland. Diurnal patterns of Alnus and Pinus pollen show distinctly lower values and low frequency of diurnal maxima between midnight and late morning and a clear rise of pollen counts at around noon. The rather high values remain during the afternoon and evening. The Betula pollen counts are almost evenly distributed along day and night and diurnal maxima appear in similar frequency at any time of day. Pollen concentrations of Poaceae increase at about 9.00 hours and remain high till late evening. Diurnal patterns of Urtica and Artemisia show very clear variation with high peaks at around 9.00 hours (Artemisia) and 13.00 hours (Urtica). The comparison of the data from Gdańsk with the data from other aerobiological stations shows very similar general features in the diurnal patterns irrespective the region or the local situation.     

Holocene tree‐line fluctuations and climate in central troms,Northern Norway

Based mainly on pollen influx data, an attempt is made at reconstructing Holocene tree‐line fluctuations and palaeotemperatures in central Troms, North Norway. Both past and present‐day (Tauber trap) pollen influx data suggest that influx rates exceeding 250–300 pollen/cm²/year for each of the major arboreal taxa (Betula pubescens and Pinus sylvestris) are only found at sites with corresponding forest types in the immediate surroundings. High influx rates, raised tree‐lines and favourable climatic periods are recorded at 7500–4500 and 3000–2600 B.P. Betula and Pinus woodlands may have reached more than 200 m above their present altitude limits, suggesting a July mean temperature 2°C higher than at present during the Holocene optimum.     

The relationship between the flowering phenophase and airborne pollen of Betula in galicia (N.W. spain)

The aim of this work was to investigate thephenological behaviour of Betula in Galicia, NW Spain, and to examine therelationship between the Betula pollencurves and the flowering phenophase. Threetrees were chosen from the each of ninepopulations of Betula located atdifferent altitudes and phytogeographicpositions. Phenological observations of theflowering periods of Betula were made ineach of them. Environmental factors such asfrequency of mist, latitudinal and topographicposition, proximity of the ocean, degree ofsolar exposure, and altitude result inphenological differences between theinvestigated populations. The correlationbetween the Pollinic Production Index of Betula pollen in Galicia and theaerobiological data of the seven monitoringstations showed that the period in which thehighest concentrations were registered wasalmost synchronous with the flowering times atmost of the phenological stations studied.Other factors such as transport and reflotationshould also be taken into account to provide anadequate interpretation of the aerobiologicaldata of Betula pollen in the atmosphere.     

澜沧江流域北部中华蜜蜂食源和营养生态位随海拔梯度的变化特征

为了解澜沧江流域北部中华蜜蜂(Apis cerana cerana)的分布,探究中华蜜蜂的食源和营养生态位沿海拔梯度的变化特征,调查了澜沧江流域北部各海拔区域中华蜜蜂的种群分布,运用蜂蜜孢粉学(melissopalynology)分析了各海拔区域中华蜜蜂蜂蜜中花粉的组成特征和变化规律,并综合分析了海拔、中华蜜蜂营养生态位和蜂蜜中花粉的相关性,探讨了自然环境与中华蜜蜂的分布,海拔梯度与蜜粉源植物、中华蜜蜂的食源和营养生态位的关系。结果表明:澜沧江流域北部中华蜜蜂的食源种类丰富,中华蜜蜂种群主要分布于2200—2800 m海拔区域。不同海拔区域中华蜜蜂采食花粉的种类和数量不同,中华蜜蜂种群分布多的海拔区域,蜂蜜中花粉的种类较多,但花粉数量相对少。随着海拔梯度升高,中华蜜蜂蜂蜜中花粉的数量表现为先降后增,而花粉的种类则表现为先增后降。不同海拔区域的中华蜜蜂营养生态位存在差异,推测各海拔区域蜜粉源植物分布、中华蜜蜂种内和种间授粉昆虫及食草动物等竞争因素不同,但各海拔梯度间的变化差异不显著。海拔与中华蜜蜂营养生态位呈正相关(r=0.051),相关性不显著;海拔与蜂蜜中花粉数量呈正相关(r=0.047),与蜂蜜中花粉种类呈正相关(r=0.144),相关性都不显著;中华蜜蜂营养生态位与蜂蜜中花粉的种类呈负相关(r=-0.305),相关性显著(P!0.05);与花粉的数量呈负相关(r=-0.064),相关性不显著。蜂蜜中花粉的数量与种类呈正相关(r=-0.303),且相关性显著(P!0.05)。     

Intraspecific variation in morphology of spiny pollen grains along an altitudinal gradient in an insect-pollinated shrub

• Intraspecific variations in pollen morphological traits are poorly studied. Interspecific variations are often associated with pollination systems and pollinator types. Altitudinal environmental changes, which can influence local pollinator assemblages, provide opportunities to explore differentiation in pollen traits of a single species over short distances. The aim of this study is to examine intraspecific variations in pollen traits of an insect-pollinated shrub, Weigela hortensis (Caprifoliaceae), along an altitudinal gradient.
• Pollen spine phenotypes (length, number and density), pollen diameter, lipid mass (pollenkitt) around pollen grains, pollen production per flower and pollinator assemblages were compared at four sites at different altitudes.
• Spine length and the spine length/diameter ratio of pollen grains were greater at higher altitudes but not correlated with flower or plant size. Spine number and density increased as flower size increased, and pollen lipid mass decreased as plant size increased. Bees were the predominant pollinators at low-altitude sites whereas flies, specifically Oligoneura spp. (Acroceridae), increased in relative abundance with increasing altitude.
• The results of this study suggest that the increase in spine length with altitude was the result of selection favouring longer spines at higher-altitude sites and/or shorter spines at lower-altitude sites. The altitudinal variation in selection pressure on spine length could reflect changes in local pollinator assemblages with altitude.

     

Holocene vegetation and water level history in two bogs of the Cordillera de Talamanca, Costa Rica

Pollen records of Holocene sediment cores from the Costa Rican Cordillera de Talamanca (La Chonta bog, 2310 m and La Trinidad bog, 2700 m) show the postglacial development of the montane oak forest zone from ca. 9500 to 1500 yr BP. During the early Holocene (ca. 9500–700 yr BP), alder vegetation covered the La Chonta and La Trinidad bogs and their adjacent hills. The upper forest line is inferred to be at 2800–3000 m elevation. A Podocarpus-Quercus forest characterised the middle Holocene (ca. 7000–4500 yr BP). The upper forest line is located at >3000 m reaching the present-day altitudinal distribution. A Quercus forest characterised the late Holocene (ca. 4500–1500 yr BP). Compared to modern conditions, the early Holocene has similar average temperatures, but the moisture level was probably higher. Pollen evidence for the late Holocene indicates drier environmental conditions than today. In order to improve the paleoecological interpretation, we described the local vegetation and used moss samples as pollen traps at both montane bogs along strong soil moisture gradients.The Netherlands Centre for Geo-ecological Research, ICG     

Vegetation, climate and palaeoaltitude reconstructions of the Eastern Alps during the Miocene based on pollen records from Austria, Central Europe

Aim To reconstruct the flora, vegetation, climate and palaeoaltitude during the Miocene (23.03–5.33 Ma) in Central Europe. Location Six outcrop sections located in different basins of the Central Paratethys in Austria. Methods Pollen analysis was used for the reconstruction of the vegetation and climate. The altitude of the Eastern Alps that are adjacent to the Alpine Foreland and Vienna basins has been estimated using a new quantification method based on pollen data. This method uses biogeographical and climatological criteria such as the composition of the modern vegetation belts in the European mountains and Miocene annual temperature estimates obtained from fossil pollen data. Results Pollen changes from Early to Late Miocene have been observed. The vegetation during the Burdigalian and Langhian (20.43–13.65 Ma) was dominated by thermophilous elements such as evergreen trees, typical of a present‐day evergreen rain forest at low altitudes (i.e. south‐eastern China). During the Serravallian and Tortonian (13.65–7.25 Ma) several thermophilous elements strongly decreased, and some disappeared from the Central European region. This kind of vegetation was progressively substituted by one enriched in deciduous and mesothermic plants. Middle‐altitude (Cathaya, Cedrus and Tsuga) and high‐altitude (Abies and Picea) conifers increased considerably during the Langhian and later on during the Serravallian and Tortonian. Main conclusions Pollen changes are related to climatic changes and to the uplift of the Alpine massifs. The vegetation during the Burdigalian and Langhian reflects the Miocene climatic optimum. The decrease in thermophilous plants during the Serravallian and Tortonian can be interpreted as a climatic cooling and can be correlated with global and regional climatic changes. This study shows that the palaeoaltitude of the eastern part of the Eastern Alps during the Burdigalian was not high enough for Abies and Picea to form a forest. Therefore, we inferred that the summits of most of the mountains would have been less than 1800 m. The substantial increase of middle‐ and high‐altitude conifers in the pollen spectra suggests that the uplift rate increased during the Langhian in this region. Based on higher palaeoaltitude estimations for the pollen floras from the studied sections of Austria, we infer that the uplift of the easternmost part of the Alpine chain continued during the Serravallian and Tortonian.     

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.     

Spring airborne pollen data in two sites in Trentino (Northern Italy): a comparison with meteorological data

In this paper airborne pollen concentration is compared to meteorological data of Trento and S. Michele all’Adige, two sites in the Adige Valley, in Trentino (North Italy). Pollen ofCorylus, Alnus, Betula andOstrya, four winter-spring flowering plants are considered. Pollen sampling was carried out in 1996 by volumetric Hirst-type samplers. For all pollen types considered, maximum pollen concentration coincided in both stations and there was a good overlap of the main pollen season length; the pollen curves of S. Michele a/A and Trento showed a highly positive correlation. The daily airborne pollen concentrations, defined as the number of pollen grains per cubic meter of air (P/m³), were compared to daily meteorological data: minimum and maximum air temperature (°C), average relative humidity (%), precipitation (mm), global incident radiation (cal/cm²), average wind direction (°) and wind speed (m/s). A highly positive correlation was found forCorylus and maximum temperature in both monitoring stations.Betula was positively, whereasOstrya was negatively correlated to relative humidity. With this first analytical approach sharp differences in the atmospheric pollen presence between the stations located at Trento and S. Michele all’Adige were not found.     

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.     

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.     

No adaptation to altitude in the invasive plant Erigeron annuus in the Swiss Alps

The altitudinal distribution of plants is restricted by various environmental factors, with climatic conditions being one of the primary constraints. Here, we investigate what limits the altitudinal range of the introduced species Erigeron annuus in the Swiss Alps. We planted offspring of E. annuus plants originating from different altitudes into two common gardens, one located at an altitude representing the main area of distribution (400 m) and the other close to the current altitudinal limit of E. annuus in Switzerland (1000 m). In both common gardens all established plants survived and grew vigorously during the growing season. However, there was high winter mortality of seedlings at 1000 m. Furthermore, plant phenology was delayed and reproductive output was reduced at 1000 m, although the seeds produced were larger. The general lack of adaptation to altitude and only moderate levels of plasticity suggest that there is little potential for E. annuus to persist beyond its current altitudinal limit in the Swiss Alps. However, climate warming might promote the upward range expansion of E. annuus by reducing winter mortality and by increasing the chance of producing seeds within the growing season.     

Beringia as a glacial refugium for boreal trees and shrubs: new perspectives from mapped pollen data

Aim Beringia, far north‐eastern Siberia and north‐western North America, was largely unglaciated during the Pleistocene. Although this region has long been considered an ice‐age refugium for arctic herbs and shrubs, little is known about its role as a refugium for boreal trees and shrubs during the last glacial maximum (LGM, c. 28,000–15,000 calibrated years before present). We examine mapped patterns of pollen percentages to infer whether six boreal tree and shrub taxa (Populus, Larix, Picea, Pinus, Betula, Alnus/Duschekia) survived the harsh glacial conditions within Beringia. Methods Extensive networks of pollen records have the potential to reveal distinctive temporal–spatial patterns that discriminate between local‐ and long‐distance sources of pollen. We assembled pollen records for 149 lake, peat and alluvial sites from the Palaeoenvironmental Arctic Sciences database, plotting pollen percentages at 1000‐year time intervals from 21,000 to 6000 calibrated years before present. Pollen percentages are interpreted with an understanding of modern pollen representation and potential sources of long‐distance pollen during the glacial maximum. Inferences from pollen data are supplemented by published radiocarbon dates of identified macrofossils, where available. Results Pollen maps for individual taxa show unique temporal‐spatial patterns, but the data for each taxon argue more strongly for survival within Beringia than for immigration from outside regions. The first increase of Populus pollen percentages in the western Brooks Ranges is evidence that Populus trees survived the LGM in central Beringia. Both pollen and macrofossil evidence support Larix survival in western Beringia (WB), but data for Larix in eastern Beringia (EB) are unclear. Given the similar distances of WB and EB to glacial‐age boreal forests in temperate latitudes of Asia and North America, the widespread presence of Picea pollen in EB and Pinus pollen in WB indicates that Picea and Pinus survived within these respective regions. Betula pollen is broadly distributed but highly variable in glacial‐maximum samples, suggesting that Betula trees or shrubs survived in restricted populations throughout Beringia. Alnus/Duschekia percentages show complex patterns, but generally support a glacial refugium in WB. Main conclusions Our interpretations have several implications, including: (1) the rapid post‐glacial migration rate reported for Picea in western Canada may be over estimated, (2) the expansion of trees and shrubs within Beringia should have been nearly contemporaneous with climatic change, (3) boreal trees and shrubs are capable of surviving long periods in relatively small populations (at the lower limit of detection in pollen data) and (4) long‐distance migration may not have been the predominant mode of vegetation response to climatic change in Beringia.     

Recent developments in monitoring and modelling airborne pollen,a review

Abstract

Public awareness of the rising importance of allergies and other respiratory diseases has led to increased scientific effort to accurately and rapidly monitor and predict pollen, fungal spores and other bioaerosols in our atmosphere. An important driving force for the increased social and scientific concern is the realisation that climate change will increasingly have an impact on worldwide bioaerosol distributions and subsequent human health. In this review we examine new developments in monitoring of atmospheric pollen as well as observation and source-orientated modelling techniques. The results of a Scopus® search for scientific publications conducted with the terms ‘Pollen allergy’ and ‘Pollen forecast’ included in the title, abstract or keywords show that the number of such articles published has increased year on year. The 12 most important allergenic pollen taxa in Europe as defined by COST Action ES0603 were ranked in terms of the most ‘popular’ for model-based forecasting and for forecasting method used. Betula, Poaceae and Ambrosia are the most forecast taxa. Traditional regression and phenological models (including temperature sum and chilling models) are the most used modelling methods, but it is notable that there are a large number of new modelling techniques being explored. In particular, it appears that Machine Learning techniques have become more popular and led to better results than more traditional observation-orientated models such as regression and time-series analyses.     

A 12 000-year record of environmental change in the Lomond Hills, Fife, Scotland: Vegetational and climatic variability

The Lomond Hills of Fife, an isolated upland area rising to over 500 m, provide an opportunity to investigate the effect of altitude on vegetation and climate in an area otherwise dominated by lower-lying land. The West Lomond site contains sediments of the Devensian Late-glacial period; they reveal a well-defined sequence of Bolling-Older Dryas-Allerod-Younger Dryas events, commencing ca. 12 190 radiocarbon years B.P. and a probable Amphi-Atlantic Oscillation between ca. 11 040 and 10 800 B.P. The Holocene record is constrained by low sediment input but does reveal a woodland presence at this altitude, dominated byBetula andCorylus. Size statistics forBetula pollen are presented and the implications of the vegetational and climatic record are discussed. The traditional view of a smooth progress towards more temperate conditions following the Younger Dryas is not supported; between 10 180 and 9120 B.P., three cooler periods are inferred, the earliest of which may belong to a terminal phase of the Younger Dryas. Comparative pollen ‘influx’ data strongly suggest thatQuercus,Ulmus andAlnus were not present locally. As a working hypothesis, it is suggested that the demise of woodland, from ca. 5950 B.P., was a result of exposure. Pollen indicative of human impact was probably derived from areas of lowland agricultural activity from ca. 5330 B.P. onwards.     

A 3-year airborne pollen and fungal spores record in San Carlos de Bariloche, Patagonia, Argentina

Airborne pollen in San Carlos de Bariloche was sampled from September to March 2001–2004 with a Hirst-type volumetric spore trap placed at a height of 15 m in a city extending from the humid forests, through the mesic forests, to the steppe. The total amount of pollen recorded varied widely from year to year. The pollen index was 4,395 in the sampling period 2001/2002; 9,055 in 2002/2003 and 2,756 in 2003/2004. The main pollen period extended from October to January. In October, pollen concentration was the highest. Sixty-six pollen types were identified. Cupressaceae and Nothofagus were the major contributors. Betula, Prunus, Pinus and Populus, the most abundant ornamental taxa in the city, also contributed to the pollen record. Pollen of Maytenus and Lomatia was representative of the mesic forest, while pollen in the lower layers of the humid forest was present in trace amounts. Cupressaceae, Nothofagus and Betula prevailed during spring (September–December), and Plantago, Rumex and Poaceae during summer (December–March). The association of daily pollen concentration and meteorological variables, temperature (mean, maximum, minimum), dew point, rainfall and wind speed, was significant. Correlations showed to be negative, with the exception of that to wind speed. The total sum of fungi spores increased from 1,771 in 2001/2002; through 8,441 in 2002/2003 to 13,782 in 2003/2004. Relative concentration rose to 29%, 48% and 84% of the total number of pollen and fungal spores recorded during each sampling period.