Poaceae Pollen Research Articles

Spatial distribution of modern pollen and fungal spores and their ecological indication in Qinghai Lake on northeastern Tibetan Plateau, China

The Qinghai-Tibet Plateau (QTP) – also called the “third pole” – is an ideal area to study the long-term relationship between people and the environment due to its sensitivity to both climate change and anthropogenic activities. Qinghai Lake in the north-eastern QTP is considered a key site to explore this issue. Fossil pollen and fungal spores extracted from lake sediments are effective proxies of palaeoecological evolution and ancient anthropogenic activities, but rely on the modern studies of pollen and fungal spores for an accurate interpretation of the fossil record. In this study, 36 surface-sediment samples from Qinghai Lake were collected from different water depths for pollen and fungal spore analyses to explore the modern characteristics of assemblages and dispersion of pollen and fungal spores. Our results show that the modern pollen assemblages of Qinghai Lake are mainly dominated by Artemisia, Cyperaceae, Poaceae, and Chenopodiaceae, with similar pollen assemblages across the lake, while pollen concentrations show a significant enrichment towards the sedimentary centres of the lake. The modern pollen assemblages reflect the characteristics of the vegetation communities and land use in the basin well. The percentages of Artemisia and Chenopodiaceae pollen are significantly higher in the lake surface-sediment samples than those from topsoil samples of the basin, while percentages of Cyperaceae pollen are lower than those in the topsoil samples. Rivers are an important vector for transporting pollen of intrazonal vegetation, including Cyperaceae, Poaceae, and Hippophae, into Qinghai Lake. Additionally, Cerealia Poaceae pollen (>37 µm) is an effective indicator of farming activities in the Qinghai Lake basin. Fungal spores have higher heterogeneity in their percentages and concentrations from different sampling sites, with Glomus spp. and Delitschia spp. being more abundant near the lakeshore, while other fungal spores, including Sordaria spp., Sporormiella spp. Pleospora spp., Coniochaeta spp., Savoryella spp., and Urocystis sp., having higher percentages and concentrations towards the centre of the lake, with the particle size of the fungal spores being an important factor affecting their transportation and deposition in the lake. This study provides essential data on modern processes and a theoretical basis for accurately interpreting fossil pollen and fungal spore records from lake sediments on the QTP.

Airborne Pollen, Allergens, and Proteins: A Comparative Study of Three Sampling Methods

Nowadays, there is a wide range of different methods available for the monitoring of pollen and allergens, but their relative efficiency is sometimes unclear, as conventional pollen monitoring does not thoroughly describe pollen allergenicity. This study aims to evaluate airborne pollen, allergen, and protein levels, associating them with meteorological and chemical parameters. The sampling was performed in Bologna (Italy) during the grass flowering period, with three different devices: a Cyclone sampler (CS), a Dicothomous sampler (DS), and a Berner impactor (BI). Total proteins were extracted from aerosol samples, and grass allergens Phl p 1 and Phl p 5 were quantified by ELISA. Airborne Poaceae pollen concentrations were also evaluated, using a Hirst-type trap. Proteins and allergens collected by CS resulted about ten times higher than those collected by the other two instruments, possibly due to their different cut-offs, while DS and BI results appeared consistent only for the total proteins collected in the fine fraction (1.3 vs. 1.6 μg/m3). Airborne proteins correlated neither with Poaceae pollen nor with its aeroallergens, while aeroallergens correlated with pollen only in the coarse particulate, indicating the presence of pollen-independent aeroallergens in the fine particulate, promoted by high wind speed.

Causal relationship between allergy and seborrheic dermatitis

Seborrheic dermatitis is a chronic relapsing inflammatory skin disease associated with overproduction of sebum and activation of the fungal skin microbiota characterized by the presence of erythematous pruritic patches and plaques with greasy scales in areas rich in sebaceous glands.Aim. To study the spectrum of sensitization to food, pollen, and indoor and fungal allergens in patients with seborrheic dermatitis.Materials and methods. The study researched features of the spectrum of sensitization to food, pollen, and fungal and indoor allergens in patients with seborrheic dermatitis (n = 40, aged 15–59 years) based on the data of an objective examination and the results of an allergen-specific test, including skin prick testing.Results. It was determined that the most significant food allergens in seborrheic dermatitis are chicken eggs and grains. The incidence of polyvalent sensitization to food allergens was 40.0%. Additionally, high incidence of sensitization to pollen allergens, most often to weed and poaceae pollen, was revealed in patients with seborrheic dermatitis. Among indoor allergens, the highest incidence of sensitization was determined to house dust and Dermatophagoides pteronyssinus. Among fungal allergens, the highest incidence of sensitization was detected to Candida albicans. Conclusion. It was found that patients with seborrheic dermatitis are often sensitized to food, pollen, and indoor and fungal allergens. Therefore, allergy can be considered a risk factor for the development of pathology.

Changes in the vegetation and water cycle of the Ecuadorian páramo during the last 5000 years

We analyzed changes in the long-term vegetation cover and in fire activity over the past 5000 years in the Ecuadorian páramo using a sediment core from Papallacta (Ecuador). The chronology is constrained by three tephra layers and 32 AMS 14C ages, and 168 samples yielded a high-resolution record of environmental changes. We estimated the upslope wind convectivity as the ratio between pollen transported from the Andean cloud forest and Poaceae pollen to distinguish changes in atmospheric moisture from changes in soil moisture. The record showed that the two sources of moisture, either from year-round adiabatic cloud dripping linked to SASM activity or to ENSO variability at decadal-scale, influenced vegetation-cover changes. Between 5000 and 2450 cal yr BP, both soil moisture and biomass burning were higher than after 2450 cal yr BP. The shift between the two states matches the zonal increase in summer insolation that drove the ITCZ to its southernmost position. Our results underline resilience to volcanic activity, the importance of the upslope convective dripping with the lowest convective index observed at ~4500 cal yr BP, the anomalous last century with the highest convective activity and the driest soil conditions recorded in the last 5000 years, the recent increase in fire activity and the link between soil moisture and the position of the ITCZ.

Estimation of absolute pollen productivity based on the flower counting approach: A review

Pollen productivity estimate (PPE) is one of the parameters necessary for pollen-based quantitative reconstruction of vegetation in the past. This paper summarizes and reviews the absolute PPEs (aPPEs) that were obtained with the area-based flower counting approach since the 1970s. The data for 23 species of trees are available from Japan and for 22 species of Poaceae from Japan, Spain, and Morocco. The aPPE values vary from 1 to 60 [1012 grains·ha−1·year−1], and are comparable to those previously reported in Europe and using different methods and approaches. The mean aPPEs of temperate conifers, such as Sciadopitysverticillata, Cryptomeria japonica, and Chamaecyparis obtusa, are as high as those of some of the common broadleaved trees, Castanea mollissima, Castanopsis cuspidata, and Alnus spp. The mean aPPEs of Abies firma, Fagus crenata, and Betula platyphylla are low, and those of Pinus densiflora, Quercus spp., Juglans ailanthifolia, Carpinus tchonoskii, Aesculus turbinata, and Poaceae spp. are intermediate. The relative PPE (rPPE) values of the arboreal taxa (relative to Poaceae), calculated using the aPPEs presented here, are smaller than those obtained in Western Europe and China based on the Extended R-value model approach. Differences in the sampling and analytical methods, as well as the interregional differences in Poaceae pollen productivity, might have contributed to the discrepancies observed. Although further studies are necessary, the flower counting approach is practical and informative for species-specific estimates of absolute pollen productivity and provides critical parameters for quantitatively reconstructing past vegetation in absolute units using the rates of pollen accumulation in sediments.

Do we need aerobiological air monitoring in desert climates? The Qatar experience.

Knowledge about diurnal, seasonal, and annual fluctuations in airborne pollen and fungal spores in any geographical area is essential for effective diagnosis and treatment of allergies. Aerobiological analysis enables the detection of airborne pollen and spores, thus providing information on plant phenology, plant distribution, related diseases, and the risks for some species in terms of allergies. Although pollen and fungal spores have been widely studied as aeroallergens throughout the world, not much is known about the biological aerosols in countries with a desert environment; and these could be present in much higher concentrations than expected. Arid desert regions (including the region surrounding the Arab Gulf), characterized by hot weather, poor soils, and low biological productivity, have typically been neglected when building ambitious biomonitoring networks for the large-scale monitoring of biological particles; however, few studies in Kuwait, Saudi Arabia, and recently Qatar have aimed to delineate the various botanical families that contribute to inhalant allergens in this region.Understanding the aerobiological features of countries with hot and desert climates may better prepare healthcare providers to assist patients with allergic rhinitis. It may be argued that one of the reasons why aerobiologists have only recently turned their attention to the state of Qatar investigating how pollen and fungal spore records could contribute to evaluating the correlation between different pollen conditions and allergy symptoms.The first aerobiological network of Qatar was monitoring (2017–2020) the atmospheric pollen concentrations of Doha and Al Khor to determine the association between the possible risk of respiratory allergies and the distribution of certain species throughout the region. In the Qatari database, more than 25 native taxa have been recorded, up to 50% of which can be considered allergenic. This includes Amaranthaceae and Poaceae pollen among the major aeroallergens causing allergy symptoms in Qatar. Our study has confirmed a statistically significant association between Amaranthaceae and asthma and allergic rhinitis. To summarize, it is worth considering aerobiological monitoring in desert climate regions when assessing the effectiveness of pollen allergy therapy and planning prevention methods for patients.

Pollen season trends as markers of climate change impact: Betula, Quercus and Poaceae

The incidences of respiratory allergies are at an all-time high. Pollen aeroallergens can reflect changing climate, with recent studies in Europe showing some, but not all, pollen types are increasing in severity, season duration and experiencing an earlier onset. This study aimed to identify pollen trends in the UK over the last twenty-six years for a range of pollen sites, with a focus on the key pollen types of Poaceae (grass), Betula (birch) and Quercus (oak) and to examine the relationship of these trends with meteorological factors.Betula pollen seasons show no significant trends for onset, first high day or duration but increasing pollen production in the Midlands region of the UK is being driven by warmer temperatures in the previous June and July. Quercus pollen seasons are starting earlier, due to increasing temperature and sunshine totals in April, but are not becoming more severe. The seasons are lasting longer, although no significant climate drivers for this were identified. The first high day of the Poaceae pollen season is occurring earlier in central UK regions due to an increasing trend for all temperature variables in the previous December, January, April, May and June. Severity and duration of the season show no significant trends and are spatially and temporally variable.Important changes are occurring in the UK pollen seasons that will impact on the health of respiratory allergy sufferers, with more severe Betula pollen seasons and longer Quercus pollen seasons. Most of the changes identified were caused by climate drivers of increasing temperature and sunshine total. However, Poaceae pollen seasons are neither becoming more severe nor longer. The reasons for this included a lack of change in some monthly meteorological variables, or land-use change, such as grassland being replaced by urban areas or woodland.

Relationship between modern pollen assemblages and vegetation in the Bashang typical steppe region of North China

Accurate knowledge of the relationship between modern vegetation and the corresponding surface pollen assemblages is the key to the quantitative reconstruction of paleovegetation and paleoclimate. The pollen assemblages of steppe regions are affected by many factors and distinguishing the pollen assemblages of different plant community types, especially Artemisia and Poaceae communities is a major difficulty in modern pollen studies in these regions. In this study we used RDA analysis to analyze modern vegetation and pollen percentage data from 119 sampling sites in different plant communities in the Bashang region of North China, which has a typical steppe vegetation. We used the results to quantitatively determine the distinguishing features of various plant community types and the relationship between the percentages of the dominant pollen types and the corresponding vegetation cover. The major results are as follows: 1) there is a clear distinction between Artemisia and Poaceae communities; in the Artemisia community, Artemisia pollen percentages are typically > 50%, and Poaceae pollen percentages are typically < 3%. In the Poaceae community, Poaceae pollen percentages are typically > 3%, and Artemisia pollen percentages are typically < 40%. 2) The Artemisia, Chenopodiaceae, Poaceae and Asteraceae are the most common vegetation types and their pollen percentages are the four most abundant types in the pollen assemblages. Their respective pollen percentages and vegetation cover show varying degrees of correlation and representativeness. Artemisia and Chenopodiaceae pollen are over-represented; that is, when the vegetation cover of Artemisia and Chenopodiaceae is < 5%, or even zero %, Artemisia and Chenopodiaceae pollen percentages can still reach 30–40%. By contrast, Poaceae and Asteraceae are under-represented in the pollen assemblages, and even where they have a high vegetation cover, their pollen percentages are rarely > 10%.

Data mining assessment of Poaceae pollen influencing factors and its environmental implications

Poaceae pollen is highly allergenic, with a marked contribution to the pollen worldwide allergy prevalence. Pollen counts are defined by the species present in the considered area, although year-to-year oscillations may be triggered by different parameters, among which are weather conditions. Due to the predominant role of Poaceae pollen in the allergenicity in urban green areas, the aim of this study was the analysis of pollen trends and the influence of meteorology to forecast relevant variations in airborne pollen levels. The study was carried out during the 1993–2020 period in Ourense, in NW Iberian Peninsula. We used a volumetric Lanzoni VPPS 2000 trap for recording Poaceae airborne pollen grains, and meteorological daily data were obtained from the Galician Institute for Meteorology and Oceanography. The main indexes of the pollen season and their trends were calculated. A correlation analysis and ‘C5.0 Decision Trees and Rule-Based Models’ data mining algorithm were applied to determine the influence of meteorological conditions on pollen levels. We detected atmospheric Poaceae pollen during 139 days on average, mainly from April to August. The mean pollen grains amount recorded during the pollen season was 4608 pollen grains, with the pollen maximum peak of 276 pollen/m3 on 27 June. We found no statistically significant trends and slight slopes for the seasonal indexes, similarly to previous Poaceae studies in the same region. The calculated C5.0 model offered defined results, indicating that the combination of mean temperature above 17.46 °C and sunlight exposure higher than 12.7 h is conductive to significantly high pollen levels. The obtained results make possible the identification of risk moments during the pollen season for the activation of protective measures for sensitized population to grass pollen.

Holocene sedimentary history of South Danamandıra Lake: a peatland in west of İstanbul, Çatalca Peninsula, NW Turkey

This study investigates the sedimentological evolution of the South Danamandıra Lake (SDL) lake in Çatalca Peninsula, 70 km west of İstanbul, using Georadar data and multiproxy analyses of five sediment cores. The lake is a 1.3-m deep, endorheic freshwater peatland, heavily colonised by common reed (Phragmites sp.). The multiproxy core investigations include a lithological core description and environmental magnetism, physical properties (gamma density and magnetic susceptibility), geochemical elemental, pollen and radiocarbon dating analyses. The lithological sequence in the lake consists of an upper peat unit and a lower sand-silt-clay unit. The peat unit is characterized by lower magnetic susceptibility, density and lithophile elements (K, Fe, Ti, and Zr) concentrations than the sand-silt-clay unit. Overall interpretation of the multiproxy data and the age-depth model suggest that the SDL was formed in a shallow depression of a fluvial channel at ca 10.9 cal kyr BP, and became a eutrophic lake at 8.1 cal kyr BP during the early Holocene warm period. Redox-sensitive element (i.e. Mn) distribution and mineral magnetic properties indicate that the peat unit has accumulated under anoxic conditions below a thin oxic surficial layer. Increase in the Taraxacum, Asteraceae, and Poaceae pollen percentages, together with high siliciclastic inputs in the lake, indicate that anthropogenic influence in the area started at 5.4 cal kyr BP.

Seasonal changes in Poaceae pollen counts in Curitiba, south of Brazil

Seasonal changes in Poaceae pollen counts in Curitiba, south of Brazil

A snapshot into the Oligocene vegetation of the Tethyan southern shores: new fossil pollen evidence from North Africa (Egypt)

A palynological investigation was carried out on 24 samples from the Oligocene Dabaa Formation, which cuts across the Amana-1X well, located in the Abu El Gharadig Basin, north Western Desert, Egypt. Palynological evidence presented here suggests an early Oligocene age for the studied Dabaa Formation. In addition, the palynological assemblages provide supplementary evidence for depositional environments. They are generally indicative of outer-shelf to upper slope environment under oxic to anoxic conditions for the lower part of the studied Dabaa Formation, but infrequent occurrences of more diverse assemblages suggest an inner neritic marine environment for strata at some levels in the upper part of the studied section. It was during the Oligocene that marked floral changes leading to the development of modern plant associations began such as temperate deciduous forests (with e.g., Acer and Betulaceae) which expanded greatly in the mid latitudes. A distinctive vegetational pattern could be outlined within the deposition of the Dabaa Formation. This pattern includes mangroves represented by taxa such as Zonocostites ramonae, Psilatricolporites crassus and Verrucatosporites usmensis. Another considerably different association with plenty of the freshwater algae Botryococcus and Pediastrum spp. at this level or tropical forests at slightly elevated altitudes (ever wet climate) are dominated by a variety of tropical forest taxa including Malvaceae and Striatricolpites, together with Retitricolporites irregularis, Psilatricolporites operculatus, Retibrevitricolporites ibadanensis, Retitricolporites spp. and Psilamonocolpites spp. in addition to ferns and tree ferns where tropical floras dominate. Also recognized are elements of savanna or open woodland (less humid climate) taxa like Poaceae pollen (grass) such as Monoporopollenites annulatus associated with Amaranthaceae (e.g., Chenopodipollis multiplex), Cyperaceae spp., Echiperiporites estelae, Proteacidites cooksonii, Cicatricosisporites dorogensis and Pteris. Finally, the montane ecosystems may have occurred at the slopes of mountains including rare pollen assigned to Sapotaceae (Psilastephanocolporites spp.) and Anacardiaceae (Retitricolpites simplex) which are probably part of the palynoflora due to long-distance transport.

Modern pollen distribution and its relationship with environmental gradient in southern Morocco

The current vegetation is affected by recurrent severe drought, pastoralism and increasing land degradation in southern Morocco. The objective of study is to evaluate the geographical distribution of pollen in southern Morocco in relation to environmental gradients and transport mechanisms, using a palynological, geochemical approach and statistical analysis. The results show that pollen of ASTEROIDEAE, CICHORIOIDEAE, POACEAE and CYPERACEAE are the most dominant in the study area. Olea/Phillyrea pollen are present mainly in semi-arid climates. Moreover, Argania spinosa pollen is endemic to southern Morocco. At the coast, pollen of CICHORIOIDEAE and CHENOPODIACEAE are the most dominant. Quercus, Artemisia and Pinus are found in the high altitudes. Towards the Saharan areas with a hyper arid and desert climate, pollen of Tamarix, Asphodelus, Acacia and Ziziphus-type seem to be the most adapted to this type of climate.The distribution of pollen in southern Morocco and their transport are controlled by surface flow, as well as the NE trade winds. It is observed that the latter are the most dominant because of the arid climate in southern Morocco, where the rivers have a temporary regime and only reach the Atlantic Ocean during exceptional rainy periods. To understand the different transport processes, we used Ti/Al and Fe/Ca ratios. These reports show high values in the Tensift and Souss-Massa Basins with regard to the Draa Basin, in parallel with the increase of CHENOPODIACEAE, ASTEROIDEAE, CICHORIOIDEAE, POACEAE, Olea/Phillyrea and CYPERACEAE pollen values indicating a dominance of transport by the trade winds.

Paleo-vegetation and environmental history of Natural Trap Cave based on pollen and carbon isotope analyses

Pollen and carbon isotope data from Natural Trap Cave provides insights into the environmental conditions of the Bighorn Basin, in north-central Wyoming, USA during the time intervals 151.1 to 132.2 cal ka BP, 51.8 to 17.4 cal ka BP, and 10.4 cal ka BP to present. Similarities between the buildup of the penultimate and last glacial maxima include abundant Artemisia, Amaranthaceae, Asteraceae, and Poaceae pollen, which, when combined with high δ13C values (>−25.0‰) and low plant discrimination values (18.0–19.0‰) from sedimentary organic matter, indicate steppe-like, cold-dry conditions. Between 151 and 142.5 cal ka BP, abundant Poaceae associated with much lower δ13C values (−28.0‰ to −26.0‰) and higher plant discrimination values (19.0‰–21.0‰) could be indicative of relatively wet summers. Similarly, after 25 cal ka BP increases in Poaceae may indicate wet conditions during the growing season. Holocene conditions differ from the earlier sections of the record, with greater arboreal pollen abundance (i.e., Pinus), consistent with woodland expansion in the region. Carbon isotope data from sedimentary organic matter show the Holocene was more humid than the glacial conditions of the late Pleistocene. This is especially clear at the start of the Holocene when a large negative carbon isotope excursion (CIE, < −28.0‰) occurred, providing a distinct chemostratigraphic marker defining the Pleistocene-Holocene boundary within these cave sediments. The association of this CIE with a pronounced spike in Pinus pollen supports an interpretation of a short-lived interval (<1000 years) of extremely warm, wet, forested conditions at this site.

Spatial and Temporal Variations of Airborne Poaceae Pollen along an Urbanization Gradient Assessed by Different Types of Pollen Traps

Grass pollen allergy is widespread all around the globe. With an increasing number of people living in cities, the examination of grass pollen levels within cities and their surroundings has increased in importance. The aim of this study was to examine different temporal and spatial scales of grass pollen concentration and deposition across urban and semi-rural environments in the years 2019 and 2020. We installed different types of pollen traps in the city of Ingolstadt (Bavaria, Germany) and its surroundings: volumetric pollen traps at roof level to assess background pollen concentration and gravimetric pollen traps and portable volumetric traps at street level. We considered grass pollen concentration and deposition in the context of land use and management. Our data showed that the grass pollen season in 2020 was longer and more intense than in 2019. Background grass pollen concentration was generally higher at the semi-rural site in both years: peak values were eight times (2019) and more than four times (2020) higher, and Seasonal Pollen Index was more than four times and almost three times higher in 2019 and 2020, respectively. Analyses of spatial variations measured at street level revealed higher numbers for pollen deposition and concentrations at semi-rural than at urban sites. Recorded values were linked to local vegetation and the management of grass areas surrounding the traps. Analyses of diurnal variations at street level in June 2019 showed that pollen concentration for all sites, independent of their degree of urbanization, were highest at noon (22.2 pollen grains/m³ vs. 8.5 pollen grains/m³ in the morning and 10.4 pollen grains/m³ in the evening). Diurnal variations at roof level showed similarities for the same days but differed when considering the whole season. Our data suggest the importance of the management of grass areas as areas cut earlier have a decreased amount of emitted pollen.

Modern Pollen Assemblages in Typical Agro-Pastoral Ecotone in the Eastern Tibetan Plateau and Its Implications for Anthropogenic Activities

Long-term evolution of human-environment interaction in the Qinghai-Tibetan Plateau (QTP) has been discussed intensively in recent years. The identification of human-related pollen types may help explore the coupled process of climate change, ecological response and anthropogenic activities on the QTP. The aim of this study is to evaluate the impact of anthropogenic activities on surface pollen assemblages and identify pollen indicators associated with grazing and cultivation in typical agro-pastoral ecotone of the eastern QTP. Totally 84 surface samples were analyzed from five vegetational communities in the eastern QTP, which are identifiable based on surface pollen assemblages. Principal component analysis of 29 pollen types and two supplementary variables of human influences were used to assess the impact of anthropogenic activities on surface pollen assemblages in eastern QTP. Severe grazing led to increase of Rosaceae, Ranunculaceae, Fabaceae, Taraxacum-Type, Aster-type and Saussurea-Type in pollen assemblages. Highland agricultural cultivation can be identified by the content and morphological characteristic of Brassicaceae and Cerealia Poaceae pollen. The aerial dispersed distances of Brassicaceae and Cerealia Poaceae pollen are very short, and domesticated herbivores are important factors, which disperse the Cerealia Poaceae pollen into pastures in agro-pastoral ecotone of the QTP. Modern pollen indicators of cultivation and grazing activity will provide precise references for fossil pollen study of prehistoric human activities in the QTP.

50 Years of Pollen Monitoring in Basel (Switzerland) Demonstrate the Influence of Climate Change on Airborne Pollen.

Climate change and human impact on vegetation modify the timing and the intensity of the pollen season. The 50 years of pollen monitoring in Basel, Switzerland provide a unique opportunity to study long-term changes in pollen data. Since 1969, pollen monitoring has been carried out in Basel with a Hirst-type pollen trap. Pollen season parameters for start dates, end dates and duration were calculated with different pollen season definitions, which are commonly used in aerobiology. Intensity was analyzed by the annual pollen integral (APIn), peak value and the number of days above specific thresholds. Linear trends were calculated with the non-parametric Mann Kendall method with a Theil-Sen linear trend slope. During the last 50 years, linear increase of the monthly mean temperatures in Basel was 0.95–1.95°C in the 3 winter months, 2–3.7°C in spring months and 2.75–3.85°C in summer months. Due to this temperature increase, the start dates of the pollen season for most of the spring pollen species have advanced, from 7 days for Poaceae to 29 days for Taxus/Cupressaceae. End dates of the pollen season depend on the chosen pollen season definition. Negative trends predominate, i.e., the pollen season mostly ends earlier. Trends in the length of the pollen season depend even more on the season definitions and results are contradictory and often not significant. The intensity of the pollen season of almost all tree pollen taxa increased significantly, while the Poaceae pollen season did not change and the pollen season of herbs decreased, except for Urticaceae pollen. Climate change has a particular impact on the pollen season, but the definitions used for the pollen season parameters are crucial for the calculation of the trends. The most stable results were achieved with threshold definitions that indicate regular occurrence above certain concentrations. Percentage definitions are not recommended for trend studies when the annual pollen integral changed significantly.

Influence of environmental drivers on allergy to pollengrains in a case study in Spain (Madrid): meteorological factors, pollutants, and airborne concentration of aeroallergens.

The aim of this study was to compare airborne levels of Phl p 1 and Phl p 5, with Poaceae pollen concentrations inside and outside of the pollen season, and to evaluate their association with symptoms in grass allergic patients and the influence of climate and pollution. The Hirst and the Burkard Cyclone samplers were used for pollen and allergen quantification, respectively. The sampling period ran from 23 March 2009 to 27 July 2010. Twenty-three patients with seasonal allergic asthma and rhinitis used an electronic symptom card. The aerosol was extracted and quantified for Phl p 1 and Phl p 5 content. Descriptive statistics, non-parametric paired contrast of Wilcoxon, Spearman's correlations, and a categorical principal component analysis (CatPCA) were carried out. Significant variations in pollen, aeroallergen levels, pollen allergen potency, and symptoms score were observed in this study. Phl p 5 pollen allergen potency was higher at the beginning of the 2010 grass pollen season. Presence of Phl p 1 outside the pollen season with positive O3 correlation was clinically relevant. 45.5% of the variance was explained by two dimensions in the CatPCA analysis, showing the symptom relationships dissociated in two dimensions. In the first one, the more important relationship was with grass pollen grains concentration and Phl p 5 and to a lesser extent with Phl p 1 and levels of NO2 and O3, and in the second dimension, symptoms were associated with humidity and SO2. Clinically relevant out-season Phl p 1 was found with a positive O3 correlation. The effect of climate and pollution may have contributed to the higher seasonal allergic rhinitis symptom score recorded in 2009.

Pollen-based mapping of Holocene vegetation on the Qinghai-Tibetan Plateau in response to climate change

Improved studies of past vegetation change are required to better understand the variation of alpine ecosystems on the Qinghai-Tibetan Plateau (QTP) in response to future climate change. Spatial and temporal variations of past vegetation can be traced by fossil pollen data mapping. In this paper, we synthesized 57 continuous pollen records on the QTP covering the past 15 kyr to depict large-scale vegetation change and its response to climate variations. In order to minimize potential chronological biases, age-depth models were revised using a state-of-the-art and consistent method for all the records. The spatial and temporal variation of major pollen taxa were examined based on interpolated pollen maps at 1000-year intervals. The arboreal pollen (AP, mainly of Pinus, Betula and Abies/Picea) content expressed significant climate signals over a broad spatial and temporal gradient. During the late glacial period, high proportions of AP widely occurred in regions that are presently unforested owing to the sparse local vegetation coverage. For the Holocene period, AP showed relatively high contributions in records from the southeastern margin of the QTP, with a decreasing gradient in abundance towards the northwest. The transportation of AP to unforested regions corresponds closely to the intensity of monsoon wind, which can be used to track the Holocene evolution of the summer monsoon. The dominant shrub and herbaceous taxa (including Artemisia, Chenopodiaceae, Cyperaceae, Poaceae and Ephedra) generally represent developments of local vegetation responding to climate variations. In addition, the persistent increase in Poaceae pollen during the mid to late Holocene correlates possibly to regional human activities. The inferred spatial and temporal patterns of major pollen types on the QTP provide significant knowledge about long-term vegetation change and its potential response to climate variations.

Characterisation of pollen seasons in Iceland based on long-term observations: 1988–2018

This paper describes a long-term (1988–2018) data series from pollen monitoring in two locations in Iceland: Akureyri and Reykjavik. Our data showed a low diversity of airborne pollen present in the aeroplankton of Iceland. We showed that Betula spp. and Poaceae can be considered the main pollen allergens in Iceland. Both Betula spp. and Poaceae pollen seasons in Iceland are characterised by a late onset compared to continental Europe. Betula spp. seasons are further characterised by a longer duration and low SPI and peak values. Icelandic Poaceae seasons are shorter, but have SPI and peak values comparable to those recorded in continental Europe. We recorded no synchronisation in the intensity of pollen production between our monitoring sites in Iceland, and our data do not confirm the existence of repeatable cycle (bi- or triennial) of high and low pollen production in Betula spp. Statistically significant trends towards increasing SPI values were recorded in Reykjavik (Betula spp.) and Akureyri (Poaceae).