Seasonal airborne pollen pattern in Mar del Plata City, Argentina

Continuous aerobiological survey of the atmosphere of Mar del Plata was carried out from December 1991 to November 1993 with a Burkard volumetric spore trap. Daily slides were prepared and studied every 2 h with standard techniques. Weekly records were kept for 27 relevant pollen types selected either by their prevalence or relative high atmospheric concentration. Quantitative multivariate analysis enabled to distinguish three major pollen seasons, related to atmospheric dominance either arboreal pollen (AP) or non-arboreal pollen (NAP). June to October is the richest period in number of pollen types, mainly dominated by AP; while from November to May, there is an overwhelming dominance of NAP types, represented by grass, herb and weed pollen. The study and prediction of this phenomenon is of great interest not only from the ecosystem point of view, but in relation to human disease as well.     

Airborne pollen and spores monitoring in Buenos Aires City: a preliminary report. Part I. Trees and shrubs (AP)

Summary The monthly trees and shrubs pollen (AP) content of the atmosphere during a whole annual period is analyzed. Thirty airborne pollen types have been identified. Most of them come from cultivated plants flowering in late winter-early spring. Thereby the annual peak is recorded in October. The highest frequencies recorded are those ofFraxinus americana, Acer negundo, Platanus spp. andMorus nigra. A second minor peak is recorded in March, and is mainly due toCasuarina spp./Myrica spp. pollen. Aeropalynological data are discussed and correlated with phytogeographical, phenological and meteorological parameters.     

An investigation of airborne pollen in Taipei city, Taiwan, 1993–1994

A two-year aeropalynological study performed during January 14, 1993 to December 31, 1994 in Taipei City revealed 154 different pollen taxa, with the most frequent beingBroussonetia (31.3%),Trema (15%),Bischofia (6.9%),Mallotus (6.8%),Cyathea (3.8%),Morus (3.7%),Fraxinus (2.9%) and Gramineae (2.8%), respectively. Two quantitative peaks of pollen grains appeared in March and in September in 1993, but only one peak in 1994. The dominant pollen taxa during these two peaks wereBroussonetia andMallotus. The heavy rain in February 1994 seemed to have delayed the first pollen peak to April, butBroussonetia was still the most frequent taxon. After July 1994, six typhoons brought heavy precipitation to northern Taiwan. Different weather types might have an effect on the concentration of airborne pollen grains, so that the timing of quantitative peaks was different in the two studied years. Arboreal pollen (AP), non-arboreal pollen (NAP) and fern spores (FS) constituted 81.7%, 7.7% and 7.8% of the two-year sum, respectively. AP dominated from January to June, NAP in November and fern spores in July. Native species in the Taipei Basin and trees along urban roadsides were the common sources of airborne pollen. The pollen calendar of two years in Taipei City was submitted.     

Pollen analysis of modern tree bark samples from the Manendragarh Forest Range of the Koriya district,Chhattisgarh, India

Pollen from modern tree bark samples collected in the Manendragarh Forest Range, Koriya District, Chhattisgarh, India, was investigated with the objective to understand the pollen rain in and around the study area, using modern tree bark samples as a new tool. The palyno-assemblages revealed the dominance of non-arboreals (herbs) over arboreals (trees and shrubs). Trees constitute an average of 17.23% pollen in the total pollen rain, whereas the average contribution of shrubs is only 0.33%. The non-arboreals have an average of 82.44% pollen in the total pollen rain. This bias in the form of representation of trees and shrubs, despite their ample presence in the forest, could be due to the differences in pollen production, dispersal and preservation of taxa, which depends on plant species and climatic conditions.     

First volumetric airborne pollen sampling in Montevideo City,Uruguay

A volumetric aeropalynological sampling was carried out for the first time in MontevideoUruguay, from October 2000 to September 2001, using a Rotorod sampler Model 40. During the year 76 pollen types were identified. Airborne pollen was recorded over the year but a maximum pollen period was observed from August to April. For the rest of the months, pollen concentration was below 1% of the total annual pollen (TP). The pollen spectrum was characterized by the dominance of herbaceous pollen (NAP), which represented 68% of the TP and dominates the spectrum from November to March. Poaceae was the most frequent and abundant pollen type accounting for 45% of TP. The pollen spectrum reflected the floristic diversity of the city and most of the sources of airborne pollen are present in local and regional flora. Fourteen pollen types reach more than 1% of the TP and most of them are cited as allergenic pollen in other regions. These results may prove important for future medical research.     

Prime indagini sulla flora pollinica aerodiffusa nella città di Messina e correlazioni meteorologiche (maggio 1985 - aprile 1986)

Abstract

Air-borne pollen census in Messina in the years 1985–1986 - Pollen of 20 herbs and weeds, and that of 14 trees or shrubs, were identified in the air of Messina (Southern Italy), in the years 1985–1986. The relative frequencies were correlated with climatic factors affecting the pollen diffusion in the studied area.     

Quantitative aeropalynology in the atmosphere of Buenos Aires city, Argentina

For the first time, a volumetric study ofBuenos Aires city atmosphere was conductedusing a Lanzoni collector from March 1997through March 1998. Fifty-four pollen typeswere recorded of which 13 had a relativeconcentration of more than 1% of the yearlytotal. The lowest concentration of pollengrains was recorded in June, when Urticas,pp., Morus spp., and Myrtaceae were low.On the other hand, the highest concentration ofpollen grains was reached in September, with anincrease in Fraxinus spp. Theaeropalynological record may be divided intothree periods: *AP Dominant from July toOctober, *NAP Dominant from November toMarch, and *Residual Period from April toJune with low pollen concentrations.The greatest number of species was recorded inNovember, when 32 types were present, and thelowest number of species in June, when only 13pollen types were recorded. In June, the pollenconcentration was not dominated by any specieswhereas in September 85% of the pollen wasderived from one species of Fraxinus.Earlier studies on the aeropalynology of BuenosAires City were performed using Tauber andRotorod samplers. They were comparable to thisstudy, especially since the pollen peak wasreached in September, although the main pollenproducing species were different.     

Aeropalynologic analysis of La Plata City (Argentina) during a 3-year period

A continuous aeropalynologic survey of the atmosphere of La Plata was carried out between July 1998 and June 2001 in order to study flowering development from winter to summer using a Lanzoni volumetric spore trap. The total pollen spectrum was represented by 79 pollen types. Between 10 and 12 pollen types showed a relative concentration of more than 1% of the annual total. Airborne pollen was mainly represented by Platanus, Fraxinus, Cupressaceae, Poaceae, Urticaceae, Cyperaceae, Myrtaceae, Celtis, Casuarina and Morus during the 3-year period. Acer and Ambrosia pollen types were only dominant in the first 2 years. Maximum absolute concentrations were recorded in the the July 1998–June 1999 period, and the minimum concentrations were recorded in the July 2000–June 2001 period. The contribution of the arboreal pollen grains was higher than 68% relative to the annual total for each year. Two periods of maximum pollen emissions were found for each year: pollen from aboreal taxa predominated from July to October, and pollen from herbaceous taxa predominated from November to March. There was very little pollen in the atmosphere between April and June. The maximum arboreal and herbaceous pollen emissions were recorded during hours of daylight: at 10:00 and 14:00 hours.     

An annual study of airborne pollen in northern Mexico City

An investigation of airborne pollen in northern Mexico City was carried out for one year. A total of 24 taxa were identified and classified according to the growing form in pollen of trees, weeds and grasses. Pollen grains were recorded all year round with a peak in December. The trees group showed the highest quantity of pollen as well as taxa diversity, although its peak period was in the dry season. The weeds and grasses emitted a larger quantity of pollen in the rainy season. The dominant taxa wereAlnus, Casuarina, Compositae and Gramineae. As for their relation with meteorological parameters, we found that the increase of pollen concentration was related to high temperatures, low relative humidity and high wind speed, the latter causing an increase of airborne pollen with no dilution at all. The hours with the highest pollen concentration where from 16:00 to 18:00.     

An annual study of airborne pollen in northern Mexico City

An investigation of airborne pollen in northern Mexico City was carried out for one year. A total of 24 taxa were identified and classified according to the growing form in pollen of trees, weeds and grasses. Pollen grains were recorded all year round with a peak in December. The trees group showed the highest quantity of pollen as well as taxa diversity, although its peak period was in the dry season. The weeds and grasses emitted a larger quantity of pollen in the rainy season. The dominant taxa wereAlnus, Casuarina, Compositae and Gramineae. As for their relation with meteorological parameters, we found that the increase of pollen concentration was related to high temperatures, low relative humidity and high wind speed, the latter causing an increase of airborne pollen with no dilution at all. The hours with the highest pollen concentration where from 16:00 to 18:00.     

A contribution to deciphering the meaning of AP/NAP with respect to vegetation cover

This study reopens the discussion on the AP/NAP ratio that contrasts the total number of Arboreal Pollen grains (AP) to that of the Non-Arboreal Pollen grains (NAP), and its meaning in terms of vegetation land-cover. Based on a set of 52 present-day pollen assemblages (mostly moss polsters) from continental France and black- and-white aerial photographs of these localities, we perform statistical analyses to clarify the meaning of the AP/NAP ratio. Short- and long-distance transported pollen grains, possible over-representation of Pinus, and distortion of cultivated plants are among the biases explored here and for which answers are given. Grey level analysis of the aerial photographs provides direct estimates of the Tree Surface/Herb Surface (TS/HS) ratio for a radius of 1000 m around the sampling point. Statistical estimates of the AP/NAP and TS/HS cut-off values separating tree- and herb-prevalent landscapes are computed. Such results obtained from modern pollen records have been applied to a Late Pliocene small maar locality from southern France characterized by a very weak pollen transport and provide the basis to further distinguish tree- and herb-prevalent landscapes in past pollen records.     

Evaluation of indoor passive pollen sedimentation over 1 year: a possible source of contamination?

The study aimed to evaluate the possible contamination by passive indoor pollen sedimentation in a laboratory where routine pollen analyses were conducted, but where no particular laboratory policies were adopted to limit contamination. Gravimetric pollen deposition was observed on traps (petri dishes soaked with glycerol) set in the palynology laboratory, under an extractor hood and on the bench beside it over 1 year (1995–1996), and in an air filtered room in a flow cabinet and on its roof over 1 month for comparison. Under the extractor hood, three types of airborne particles were deposited: pollen grains, spores and algae, representing 32.35, 67.28 and 0.37%, respectively, of the total sedimented particles over 1 year. The number of pollen grains deposited on the surface trap ranged from 0 (27 November to 4 December 1995) to 707 (10–18 April 1995). The highest number of taxa during a weekly collection was 23 (9–15 May 1995). The pollen flora represented by anemophilous pollen (>90% of the trapped pollen) was related to the vegetation next to the laboratory:Acer, Carpinus, Castanea, Corylus, Cupressaceae, Pinus, Quercus, Salix, Taxus for trees and shrubs andArtemisia, Brassicaceae, Plantago, Poaceae, andUrticaceae for grasses and weeds. Indoor pollen deposition corresponded to the period of the outdoor pollination (macroscopic field observation) which lasted from March to the beginning of August. However, some pollen were almost always present in the collection (Poaceae, Salix, Castanea, Betula), reflecting the occurrence of pollen grains in the atmosphere out of the pollination period. Moreover, about five times more entomophilous pollen was found under the extractor hood compared to the other area of the laboratory; even in the flow cabinet of the air filtered room, 237 particles were captured (versus only 15 on the roof). These data suggest a possible human contamination during operations under the extractor hood or in the flow cabinet. Although few airborne pollen were found, possible contamination has to be considered in investigations where even low pollen quantities are of interest.     

重庆喀斯特地区现代花粉组合与植被的关系

重庆喀斯特地区4种不同地貌单元的81份表土和苔藓样品的孢粉分析结果表明:(1)研究区植物孢粉组合共由109科属组成。除金佛山外,其他植被退化严重地区样点均以草本和蕨类植物占据优势(剔除石漠化治理大量引种的马尾松、柳杉和侧柏等乔木花粉),其次是乔木植物花粉(主要为马尾松),灌木植物花粉含量很低,显示该区植被退化严重;(2)孢粉组合的PCA分析能够很好地将研究区的现代孢粉组合区分开来,较好地反映了重庆喀斯特地区不同地貌单元的植被特征,特别是石漠化区植被退化严重的孢粉组合特征。生态保护较好、自然植被发育的金佛山地区具有106科属的乔木、灌木与草本孢粉类型,以及高含量的乔木花粉,而喀斯特石漠化地区的鸡公山(46科属)、青木关镇(56科属)和南平镇(50科属)则表现为乔灌木孢粉类型较少;(3)银杉作为金佛山特有的孑遗植物,其花粉含量明显低于松属花粉,说明其花粉不利于远距离传播;(4)随着土地利用强度的增加,现代孢粉组合中乔灌木花粉含量和种类越少,草本和蕨类植物孢粉含量越多,且以耕地杂草为主。因此,土地利用方式的变化是喀斯特石漠化区次生植被及其现代孢粉组合变化的主要影响因素。研究可为重庆喀斯特地区土地利用策略的制定,重庆及其周边地区第四纪古植被、古气候和古环境重建研究,以及中国孢粉数据库建设提供基本数据和科学依据。     

Santa Lucia superiore (Toirano, Ligurie) : reconstitution locale de la végétation ligure durant le Pléniglaciaire ancien

Pollen analysis of Santa Lucia superiore cave (Italy) reports at local scale the lowland Ligurian vegetation during the Lower Pleniglacial (75 to 57 Kyr BP). The pollen profile shows two AP extensions during a steppe-landscape episode in Liguria. The dry and cold phases caused the establishment of a steppe-landscape (NAP 92%) with Artemisia, Ephedra, Poaceae and Chenopodiaceae, similar to those mentioned in the Latium during the Pleniglacial. The increase of moisture generated a first arboreal extension (Pinus, Betula, Corylus, Ulmus), which engendered the formation of an open-forest landscape (AP 43%). The second arboreal extension (AP 55%) was due to an increase of moisture and higher temperatures, which allowed the development of Mediterranean trees and shrubs (Quercus ilex, Olea, Phillyrea). This warming up occurred probably simultaneously with a secondary transgression during the glacial sea-level change. The upper part of the profile shows an open vegetation, which indicates the return of a steppe-landscape. Pollen data, replaced in the multidisciplinary studies of the site, are well correlated with the fauna and sediment data.     

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.     

Pollen availability and abundance of predatory phytoseiid mites on natural and secondary hedgerows

Mites occurring on a number ofnatural and secondary (i.e., planted) hedgerowslocated in north-eastern Italy were monitoredwith particular attention being paid tophytoseiids (Acari: Phytoseiidae). Pollendiversity and abundance were analysed tohighlight potential relationships betweenpollen availability and phytoseiids. Secondaryhedgerows were structured in modules containinga single species (field maple, hornbeam,dogwood, hazel, and elderberry) andmodules containing a mixture of theabove-mentioned species. These hedgerows werelocated in an experimental farm where they werecontiguous to a vineyard. Natural hedgerowswere located in the same area. The pollen ofPoaceae was the most important component ofnon-arboreal pollen (NAP), and that ofelderberry of arboreal pollen (AP). Pollendiversity was higher on natural than onsecondary hedgerows. Generally, pollendensities reached relatively high levels fromlate April to late June and decreased insummer. Pollen was more abundant on naturalthan on secondary hedgerows and phytoseiidabundance showed a similar trend. On elderberryand hornbeam in natural hedgerows a potentialrelationship between pollen availability andthe abundance of phytoseiids, in particular ofEuseius finlandicus (Oudemans) was found.Experimental pollen applications increased thefecundity and the abundance of this species.     

Circadian periodicity of airborne pollen and spores; significance of sampling height

Summary The circadian periodicity of the five allergologically most important pollen types in S. Finland and two different spore types were studied at two sites, about 200 meters apart: one Burkard sampler situated on a roof at a height of 15 meters and the other on a garden lawn at ground level. The circadian rhythms of pollen released close to the ground (herb pollen) did not correlate at the two sampling heights used. Variations in pollen from high sources (trees) were significantly correlated at the two heights used. The circadian rhythms of spores from low source distant from the sampling sites (Suillus as an example of forest fungi) were not always correlated; instead, spores with sources at different heights (Cladosporium as an example) had similar circadian periodicity not depending on the sampling level. It was shown that, when studying circadian rhythms of atmospheric particles, the sampling height used is often of great importance. Circadian rhythms of the same pollen and spore types for ten years at the higher sampling site are presented for long-term comparison.     

Modern pollen samples from alpine vegetation on the Tibetan Plateau

• 1 A set of 316 modern surface pollen samples, sampling all the alpine vegetation types that occur on the Tibetan Plateau, has been compiled and analysed. Between 82 and 92% of the pollen present in these samples is derived from only 28 major taxa. These 28 taxa include examples of both tree (AP) and herb (NAP) pollen types.
• 2 Most of the modern surface pollen samples accurately reflect the composition of the modern vegetation in the sampling region. However, airborne dust‐trap pollen samples do not provide a reliable assessment of the modern vegetation. Dust‐trap samples contain much higher percentages of tree pollen than non‐dust‐trap samples, and many of the taxa present are exotic. In the extremely windy environments of the Tibetan Plateau, contamination of dust‐trap samples by long‐distance transport of exotic pollen is a serious problem.
• 3 The most characteristic vegetation types present on the Tibetan Plateau are alpine meadows, steppe and desert. Non‐arboreal pollen (NAP) therefore dominates the pollen samples in most regions. Percentages of arboreal pollen (AP) are high in samples from the southern and eastern Tibetan Plateau, where alpine forests are an important component of the vegetation. The relative importance of forest and non‐forest vegetation across the Plateau clearly follows climatic gradients: forests occur on the southern and eastern margins of the Plateau, supported by the penetration of moisture‐bearing airmasses associated with the Indian and Pacific summer monsoons; open, treeless vegetation is dominant in the interior and northern margins of the Plateau, far from these moisture sources.
• 4 The different types of non‐forest vegetation are characterized by different modern pollen assemblages. Thus, alpine deserts are characterized by high percentages of Chenopodiaceae and Artemisia, with Ephedra and Nitraria. Alpine meadows are characterized by high percentages of Cyperaceae and Artemisia, with Ranunculaceae and Polygonaceae. Alpine steppe is characterized by high abundances of Artemisia, with Compositae, Cruciferae and Chenopodiaceae. Although Artemisia is a common component of all non‐forest vegetation types on the Tibetan Plateau, the presence of other taxa makes it possible to discriminate between the different vegetation types.
• 5 The good agreement between modern vegetation and modern surface pollen samples across the Tibetan Plateau provides a measure of the reliability of using pollen data to reconstruct past vegetation patterns in non‐forested areas.

     

A neotaphonomic experiment in pollen oxidation and its implications for archaeopalynology

Oxidation is considered to be a major taphonomic process involved in differential pollen preservation. An experimental protocol has been developed in the laboratory to test the impact of oxidation on pollen concentrations. Seven modern pollen taxa were selected among common trees, shrubs and herbaceous plants from the European flora, with regard to their typical pollen morphology (Pinus, Alnus, deciduous Quercus, Cichorioideae, Caryophyllaceae, Ericaceae and Poaceae). An aqueous solution of potassium permanganate (KMnO₄) was used to oxidise the pollen grains. The impact of oxidation was measured as a function of increasing oxidation intensity and increasing exposure time. For each taxon, the pollen concentration (grains µl⁻¹) was measured following each oxidation stage. The results show that all pollen taxa are affected by oxidation. Both low oxidant concentrations and short oxidation exposure times led to a fast decrease in pollen concentrations. The thickness of the exine and a specific morphology appear to be the deciding factors controlling the ability to withstand oxidation. A simulation of the impact of oxidation was performed on two model pollen spectra simulating a forested and an open environment. Significant differences were recorded between the initial and final pollen rates. The AP/NAP ratio is modified to a greater extent in the spectrum associated with the open environment. However, over-representation of a specific taxon in a pollen spectrum cannot be attributed to the impact of oxidation alone. For instance, when Cichorioideae are recorded with high frequencies in pollen analyses carried out in an archaeological context, oxidation should not be regarded as the only taphonomic process responsible for this over-representation. The differential conservation of pollen is a complex process in which oxidation represents but one of a variety of interacting taphonomic factors (such as pollen transport, bacterial activity, temperature, pH, hygrometry).     

Vegetation in the mountains of northwest Iberia during the last glacial-interglacial transition

A new core taken from a site in the Sierra de Courel range of mountains in the northwest Iberian peninsula, Spain, enables a palaeoenvironmental reconstruction to be made of the biological events resulting from climatic changes and human activities during the last 17,000 years in the area. The sequence begins with a phase characterised by the dominance of Gramineae (Poaceae) and Pinus. A markedly arid period with prevalence of Artemisia pollen occurred between 17,5000 and 15,500 uncal. B.P. Subsequently, a succession of woodlands with Betula, Pinus and other mesophilous and thermophilous trees was recognised during the period 15,500-13,500 uncal. B.P. Between 13,500 and 10,300 uncal. B.P. herbaceous vegetation formations indicating moister conditions dominated the pollen record, although a maximum of Gramineae has been dated during the period 11,300-10,300 uncal. B.P. Comparison with other pollen data from neighbouring mountains allows an interpretation of the vegetation changes during the glacial/interglacial transition in the mountains of northwest Iberia. The Holocene pollen record from the site does not differ markedly from other records in the area, tree expansion occurring before 10,000 uncal. B.P. and high values of deciduous Quercus mixed with other trees and shrubs persisting until 3500 uncal. B.P., when increased human activities are shown by a fall of the tree pollen percentages. Received July 7, 1999 / Accepted May 22, 2000