Poaceae Pollen Research Articles

Multiporate Poaceae pollen grains observed in the recent fossil record from the Greater Serengeti Ecosystem and Lake Victoria region

Multiporate Poaceae pollen grains observed in the recent fossil record from the Greater Serengeti Ecosystem and Lake Victoria region

A 23-million-year record of morphological evolution within Neotropical grass pollen.

Grass-dominated biomes in South America comprise c. 20 million years of history, yet their evolution and underlying drivers remain poorly understood. Here we apply a novel approach that combines scanning electron microscopy imaging with computational analysis to quantify the morphometrics of grass (Poaceae) pollen micro-ornamentation from the Neotropics since the Early Miocene (23 million years ago). Three spatial-temporal pollen sets were assembled to further elucidate the variation and evolutionary traits of grasses through space and time. Our results reveals that three spatial-temporal pollen groups occupy unique, partially overlapping regions of their exine morphospace. The direction of this shift is consistent over time, progressing towards less dense ornamentation. Interestingly, the extent of the occupied morphospace did not vary significantly. This is the first time that the true morphological variation in Poaceae pollen micro-ornamentation becomes apparent through time. We hypothesize that changes in grass pollen exine since the Early Miocene were driven by evolutionary processes (evolutionary drift and/or directional selection), and potentially migration at the continental scale. The high diversity in pollen micro-ornamentation is likely related to their evolutionary success in the Neogene.

Poaceae Pollen as the Leading Aeroallergen

The relevance of aerobiological topics is evidenced by the fact that from July 1 to July 5, 2024, an unusual event was held in Vilnius (Lithuania), including the 8th European Symposium on Aerobiology (8th ESA), the 12th International Congress on Aerobiology (12th ICA) and the 5th International Ragweed Conference (5th IRC). World Aerobiology 2024 is an event of unprecedented scale. It discussed the use of artificial intelligence (AI) for calculating and interpreting aerobiological monitoring data. But so far, AI cannot identify all taxa, so careful counting and identification of plant pollen and fungal spores is only possible for a human researcher. Aerobiological monitoring using volumetric traps remains the gold standard of research. In the world community, there are networks of biological monitoring of air quality with the study of the concentration of plant pollen and fungal spores in the air. Through an application on a mobile phone, you can find out the forecast of periods of maximum risk, during which patients with hay fever are exposed to the main aeroallergens. Popular queries from Internet users relate to the complex problem of climate change, environmental pollution and aeroallergens. There is no National Aerobiological Monitoring system in Kyrgyzstan, but the Meteonova service has launched a pollen forecast application for mobile phones, which is still in the testing stage and does not reflect the real features of the aerobiological spectrum. It is known that in the world there are more than 12,000 species in the Poaceae family, classified into 771 genera belonging to 12 subfamilies. In Kyrgyzstan, 300 anemophilous species of annual perennial plants grow, releasing a huge amount of pollen into the atmosphere in the spring and summer. Poaceae pollen is still one of the top ten global aeroallergens, being the leading cause of hay fever, by predominant size, classified as biological pollutants (PM10). The concentration of cereal pollen was consistently observed in the air of Karakol during all seasons of the study and ranged from 167 to 174 days. Its daily maximum concentrations were detected in June-July; the distribution of pollen in the air is unimodal. The influence of the anthropogenic triad on fluctuations in the concentration of cereal pollen was established: climate change (temperature) and land use systems, as well as environmental pollution, which manifested itself in the degradation of pollen grains and the appearance of damaged and unidentified biological particles. The purpose of this article is to study the concentration of cereal pollen in the air, their integrative contribution to the aerobiological spectrum in the city of Karakol as dominant pollen allergens.

Forecast models for start and peak dates of Poaceae pollen season in Tétouan (NW Morocco) using multiple regression analysis.

Poaceae pollen is one of the most widespread sources of aeroallergens in the world. The aim of this study is to build predictive models for the pollen season start day (PSsd) and peak dates of the Poaceae pollen season and thus give an overview of the climatic parameters that have the greatest influence. In Tétouan, sampling was carried out using a volumetric spore trap of the Burkard Hirst type. The relationships between the PSsd, peak dates and meteorological parameters were determined using correlation analysis. The models were constructed using multiple regression analysis with data from 2008 to 2019 and tested on data from 2022. The PSsd was especially significantly influenced by minimum temperature during winter and precipitation in the autumn of the previous year. The peak dates were significantly correlated with precipitation in January, March and April, but not with temperature. Three models were obtained for each of the season's parameters; the most accurate model for the PSsd explained a variability of 61% and includes as main predictors rainfall from the autumn of the previous year and the mean daily average temperature from 23 February to 8 March. The two most efficient peak dates models included precipitation in January and April as the main predictor variables, and explained greater variability (87 and 88%). Precipitation in autumn and the mean daily and the sum of minimum temperature in winter, showed significant decreasing tendencies. However, the PSsd trend delay was not statistically significant. This study draws the importance of the weather during preseason for grass pollen production and emphasises the usefulness of the models for allergic patients to take preventive measures and for healthcare professionals in allergy therapy.

Development of a landscape in NE Minnesota, from the Early Holocene to Forest-harvesting, Agriculture and Industry

An array of lake sediment proxies including paleobotanic, geochemical, and historical records has been used to determine former environments of Bugbee Pond, a small, mesotrophic pond in northeastern Minnesota. Much research has been produced on the history of climate and vegetation change of the region, yet we have little information on the impact of human settlement. This well-dated, high resolution, multi-proxy record is important for its length and concentration on the historic period. The lake itself became established by ~7000 years ago. Pollen evidence suggests a transition between the regional Prairie Period to the Great Lakes mixed conifer – hardwood forest was established in the region at this time. XRF data suggest dry basin accumulation early in the record after ~7000 cal yr BP, but lake levels substantially increased by ~5600 cal yr BP, during a regionwide climatic transition to more humid conditions. Birch and boreal conifers increased after about 3800 cal yr BP; further increases in boreal conifers occurred by ~2000 cal yr BP. Anthropogenic vegetation changes during the Historic period, beginning in the late 19th century, is well represented by forest clearance of white pine ( Pinus strobus), followed by increases in early successional species and an increased sediment accumulation rate due to land clearance. Establishment of farming communities locally are shown by occurrence of corn ( Zea mays) and oat ( Avena sativa) pollen, and pasturing and grazing are documented by Rumex, Fabaceae and Poaceae pollen, as well as coprophilous fungi, such as Sordaria. The increase and subsequent decline in Pb and S concentrations in the uppermost sediments are mirrored by historically documented, nearby industrial activities.

Environmental DNA analysis of airborne poaceae (grass) pollen reveals taxonomic diversity across seasons and climate zones

BackgroundGrasses populate most biogeographical zones, and their diversity influences allergic sensitisation to pollen. Previously, the contribution of different Poaceae subfamilies to airborne pollen has mostly been inferred from historical herbarium records. We recently applied environmental (e)DNA metabarcoding at one subtropical site revealing that successive airborne grass pollen peaks were derived from repeated flowering of Chloridoid and Panicoid grasses over a season. This study aimed to compare spatiotemporal patterns in grass pollen exposure across seasons and climate zones. MethodsAirborne pollen concentrations across two austral pollen seasons spanning 2017–2019 at subtropical (Mutdapilly and Rocklea, Queensland) and temperate (Macquarie Park and Richmond, New South Wales) sites, were determined with a routine volumetric impaction sampler and counting by light microscopy. Poaceae rbcL metabarcode sequences amplified from daily pollen samples collected once per week were assigned to subfamily and genus using a ribosomal classifier and compared with Atlas of Living Australia sighting records. ResultseDNA analysis revealed distinct dominance patterns of grass pollen at various sites: Panicoid grasses prevailed in both subtropical Mutdapilly and temperate Macquarie Park, whilst Chloridoid grasses dominated the subtropical Rocklea site. Overall, subtropical sites showed significantly higher proportion of pollen from Chloridoid grasses than temperate sites, whereas the temperate sites showed a significantly higher proportion of pollen from Pooideae grasses than subtropical sites. Timing of airborne Pooid (spring), Panicoid and Chloridoid (late spring to autumn), and Arundinoid (autumn) pollen were significantly related to number of days from mid-winter. Proportions of eDNA for subfamilies correlated with distributions grass sighting records between climate zones. ConclusionseDNA analysis enabled finer taxonomic discernment of Poaceae pollen records across seasons and climate zones with implications for understanding adaptation of grasslands to climate change, and the complexity of pollen exposure for patients with allergic respiratory diseases.

Holocene histories of biome stability in northern Amazonian savannas

Paleoecological analysis of three lake sediment cores from the Roraima savannas in northern Brazil revealed systems dominated by Poaceae pollen throughout most of the Holocene. A slight increase of palms and woody taxa, probably linked to wetter conditions, is observed during the last 1000 years but is more noticeable after 300 and 150 calibrated years BP (yr BP) respectively. Charcoal was present throughout affirming the importance of fire for the landscape but showed the highest values mostly in the last millenium. Poaceae pollen size spectra varied considerably, showing more variability than the overall pollen record. Despite evidence of some climate change in the Holocene, these savannas were stable systems. The sedimentary records showed gaps in deposition between 10,000 and 7800 yr BP and between 2500 and 1200 yr BP, suggesting dry periods during which lakes most likely dried out or became impermanent and highlighting the sensitivity of these lakes to local water table variation. The establishment of the modern climate in the region is evident after 1000 yr BP.

Modern pollen assemblages of agricultural land, wasteland, and natural vegetation in China and their significance for reconstructing the intensity of agricultural activity

Knowledge of the modern pollen assemblage characteristics of artificial and disturbed vegetation can help reconstruct changes in the intensity of human activity and land use/land cover (LULC) based on Holocene stratigraphic pollen records. We obtained pollen assemblage data from 217 agricultural land (cultivated cereals) sites, 79 wasteland sites, and 389 natural vegetation sites in different regions in China. The results show that the pollen of cereals Poaceae and the associated agricultural weeds in agricultural land and wasteland vegetation contexts are effective indicators of the intensity of agricultural activity, and that the pollen assemblages of natural vegetation accurately reflect the regional zonal vegetation composition. Although the cereals Poaceae proportion varied greatly among the agricultural sites in different regions, due to factors like cultivation practices, crop types, and terrain, all of them were significant indicators of agricultural activity. The pollen assemblages of wasteland and natural vegetation in different regions were also different, and the indicator taxa exhibit distinct zonal characteristics. There was no consistent linear relationship between cereals Poaceae proportion and the area of agricultural land. The cereals Poaceae proportion did not vary with increasing agricultural area in regions with higher or lower levels of agricultural production; only in Northeast and North China, when the agricultural area was below 60%, did the cereals Poaceae proportion increase with increasing agricultural area. These results provide a modern process basis for the use of stratigraphic pollen data to reconstruct past changes in agricultural activity and LULC.

Palynology of sedimentary soils in the Pampa biome: Grassland-forest mosaics and landscape-soil-pollen relationships

Pampa biome vegetation is characterized by extensive areas of native grassland, interspersed with forests close to water courses. An understanding is been searched on how grassland and forest dynamics to contribute for the conservation and management practices suitable for the biome. The objective of this study was to asses if landscape-soil-pollen relationships are determinant of grassland-forest mosaics, by analyzing summit, footslope and toeslope positions in the landscape, in the Campanha region of the Pampa biome. We collected 32 samples in three soil profiles in topossequence under natural grassland of the Pampa biome, in southern Brazil. These samples were treated following standard methodology used in palynology studies. The pollen percentage diagrams were generated to represent the identified pollen set, while cluster analysis was used to define the paleoecological zones. The results found were supported by radiocarbon dating (age of subsurface soil varying from 3,460 to 4,090 calibrated years before present), and particle-size analysis. The paleoecological zones, for each soil profile, indicate a predominance of grassland vegetation, especially Poaceae pollen, whereas Fabaceae and Piper were predominant in forest sites. The pollen set obtained in the three soil profiles indicates hegemony of the sites, even under climatic conditions of increased moisture. Rare pollen grains from forest taxa suggests that trees and shrubs existed in isolated form. The presence of bryophyte spores and taxa associated with soil wetness indicates that the region was once dominated by extensive wetlands and moist landscapes. Our findings enhance the comprehension of the Pampa flora, and are applicable in restoration of degraded areas. The preservation of pollen grains in soil profiles shows the potential of minerals soils to reconstitute Pampa biome vegetation, representing a site for palynological research advance, and demonstrate grassland formations maintain their supremacy even under unfavorable climatic conditions. Thus, this study expands the frontier of palynological work, encompassing new sites and new opportunities to evaluate land use/land cover changes.

Grass pollen surface ornamentation is diverse across the phylogeny: Evidence from northern South America and the global literature

AbstractThe grasses are one of the most diverse plant families on Earth. However, their classification and evolutionary history are obscured by their pollen stenopalynous (similar) morphology. A combination of high‐resolution imaging of pollen surface ornamentation and computational analysis has previously been proposed as a promising tool to classify grass taxonomic boundaries. In this study, we test this hypothesis by studying Poaceae pollen across the phylogeny from plants collected in northern South America and also from published literature across the globe. We assessed if morphotypes that we establish using descriptive terminology are supported by computational analysis, if they vary along six (a)biotic variables and vary across the phylogeny. Based on this analysis, we constructed a reference framework for pollen surface ornamentation morphotypes. Our results showed that there is a wide variation of grass pollen surface ornamentation. We identified nine new and confirmed six known morphotypes, establishing a data set for 223 species (243 individual plant specimens) that represent 11 subfamilies. Computational analysis showed that our morphotypes are well‐supported by two quantitative features of pollen sculptural elements (size and density). The specific data set and mapping of the phylogeny confirmed that pollen morphological sculpture is unrelated to (a)biotic variables and is diverse across the phylogeny.

Investigation and analysis of airborne allergenic pollen in 4 districts and 5 counties of Hohhot City

Objective: To investigate the species, concentration and seasonal trends of main airborne allergenic pollen in 4 districts and 5 counties of Hohhot City. Methods: The Department of allergy, Beijing Shijitan Hospital Affiliated to Capital Medical University conducted a cross-sectional study about monitoring the airborne allergenic pollen from August 1, 2021 to July 31, 2022 by the gravitational method in 4 districts and 5 counties of Hohhot City, which include Yuquan District, Xincheng District, Huimin District, Saihan District, Tuoketuo County, Helingeer County, Tumotezuoqi County, Wuchuan County and Qingshuihe County. Daily pollens were counted and identified by optical microscopy, and the data were analyzed. Results: The airborne allergenic pollen was collected every month all year round in 4 districts and 5 counties of Hohhot city. Through the whole year of the total quantity of pollens ranged from 24 850 to 50 154 grains per 1 000 mm2 and two peaks of pollen concentration in air were observed,which happened in spring (from March to May) and in summer and autumn (from July to September). In spring, the main pollens were tree pollens, which principally distributed in Populus pollen (18.29%), Ulmus pollen (8.36%), Pinus pollen (6.20%), Cupressaceae pollen (5.23%), Betulaceae pollen (2.73%), Salix pollen (1.80%) and Quercus pollen (1.16%). In summer and autumn, the main pollens were weed pollens, which mainly included Artemisia pollen (42.73%), Chenopodiaceae pollen or Amaranthaceae pollen (7.46%), Poaceae pollen (2.26%), Humulus pollen or Cannabis pollen (0.60%). Conclusion: There were two peaks of main airborne allergenic pollen in 4 districts and 5 counties of Hohhot City. In the spring peak of pollen, the main airborne pollens were tree pollens. In the summer and autumn peak of pollen, the main airborne pollens were weed pollens. The Artemisia pollen was the most major airborne pollen in this area.

A real-time calibration method for the numerical pollen forecast model COSMO-ART

Technologies for monitoring pollen concentrations in real-time made substantial advances in the past years and become increasingly available. This opens the possibility to calibrate numerical pollen forecast models in real-time and make a significant step forward regarding the quality of pollen forecasts. We present a method to use real-time pollen measurements in numerical pollen forecast models. The main idea is to calibrate model parameterizations and not to assimilate measurements in a nudging sense. This ensures that the positive effect persists throughout the forecast period and does not vanish after a few forecast hours. We propose to adapt in real-time both the model phenology scheme and the overall tuning factor that are present in any numerical pollen forecast model. To test this approach, we used the numerical pollen forecast model COSMO-ART (COnsortium for Small-scale MOdelling-Aerosols and Reactive Trace gases) on a mesh size of 1.1 km covering the greater Alpine domain. Test runs covered two pollen seasons and included Corylus, Alnus, Betula and Poaceae pollen. Comparison with daily measurements from 13 Swiss pollen stations revealed that the model improvements are large, but fine-tuning of the method remains a challenge. We conclude that the presented approach is a first valuable step towards comprehensive real-time calibration of numerical pollen forecast models.

Vegetation History of Lake Marmara (W. Türkiye) and Surrounding Area during the Last 700 Years

In this study, a 65 cm long sediment core was obtained for pollen analysis from Lake Marmara situated in the west of Türkiye. The bottom sediment was dated by one AMS radiocarbon date on bulk organic carbon. Thus, the core provides information about the vegetation history of the lake for the last 700 years. Palynological evidence indicates that the vegetation around the lake basin was dominated by Quercus (evergreen oaks) and Pinus. The presence of Olea, Juglans, and Poaceae pollen grains reveals that this forest vegetation was interrupted from time to time by human impact. The existence of the non-arboreal Taraxacum and Plantago in the uppermost zones of the pollen diagram also indicates grazing or deterioration of the vegetation cover in this region from 1568 AD to the present.

Effects of Fabaceae and Poaceae Pollen Accessibility and Traits on the Pollinivory of Adult Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae).

Pollen is a food source for adult Chrysoperla externa(Hagen), whose larvae are biocontrol agents against pests. However, adults may face challenges in foraging for pollen due to differences in pollen accessibility and variability in pollen morphology and chemistry. In the laboratory, we investigated the ability of adult C. externa to consume pollen from flowers of Cajanus cajan, Canavalia ensiformis, Crotalaria juncea, Flemingia macrophylla, Avena strigosa, Pennisetum glaucum, Sorghum bicolor, and Zea mays, and we explored whether adults chose any of these pollens based on their quantitative and qualitative features. Cajanus cajan and F. macrophylla pollen were the only ones not consumed by adults when confined to flowers. Pollen removed from the preanthesis buds was offered simultaneously for 24 and 48h. In both periods, adults consumed more of the medium-sized P. glaucum (with the second largest exine thickness) and large-sized Z. mays (with the thinnest exine) pollen, even though they had significantly less crude protein than Fabaceae pollen, whose sizes varied from medium (C. juncea, with the thickest exine) to large (C. ensiformis, whose exine thickness was equal to that of P. glaucum). Overall, adults consumed more Poaceae pollen than Fabaceae pollen, but the palynological features and the protein contents did not affect this choice. Our results highlighted that C. juncea, P. glaucum, S. bicolor and Z. mays are good pollen sources for adult C. externa and should be considered promising candidates in the selection of insectary plants to deploy in biocontrol programs aimed at the conservation of this lacewing.

Comparison of airborne Cupressaceae, Quercus and Poaceae pollen between Tulsa (Oklahoma) and Córdoba (Spain)

This study focuses on the pollen season timing and intensity, and the influence of weather conditions, on airborne Cupressaceae, Quercus, and Poaceae pollen in two different biogeographical areas, Córdoba (Spain) and Tulsa, Oklahoma (USA), during 2010–2014. Pollen concentrations were recorded using Hirst-type spore traps. The meteorological parameters studied included temperature, relative humidity, wind speed, and rainfall. This study aims to define the pollen seasons and their intensity and relationships with meteorological parameters in different biogeographical areas. The main pollen season (MPS) of each pollen type was divided into two periods: pre-peak and post-peak. The Shapiro–Wilk normality test was applied to the pollen concentrations and log transformed data were used. Pearson correlations and linear regression were applied for the pre-peak, post-peak, and MPS for comparing pollen concentrations with meteorological parameters considering both the same day and the previous day. Then, multiple regression analysis was applied with all the meteorological parameters that showed significant results in the linear regression. The models were validated through correlations between the measured and predicted pollen concentrations. The results showed a small difference in the MPS for the different pollen types at each site. Temperature, relative humidity, and rainfall influenced the pollen concentrations. The same day's meteorological parameters usually had a greater impact on the pollen concentration than the previous day's meteorological parameters; although, pollen concentrations for the next day could be forecasted considering the meteorological parameters forecasted for the present day. The pollen concentrations showed greater correlations with temperature.

Constructing a pollen proxy from low-cost Optical Particle Counter (OPC) data processed with Neural Networks and Random Forests

Pollen allergies affect a significant proportion of the global population, and this is expected to worsen in years to come. There is demand for the development of automated pollen monitoring systems. Low-cost Optical Particle Counters (OPCs) measure particulate matter and have attractive advantages of real-time high time resolution data and affordable costs. This study asks whether low-cost OPC sensors can be used for meaningful monitoring of airborne pollen.We employ a variety of methods, including supervised machine learning techniques, to construct pollen proxies from hourly-average OPC data and evaluate their performance, holding out 40 % of observations to test the proxies. The most successful methods are supervised machine learning Neural Network (NN) and Random Forest (RF) methods, trained from pollen concentrations collected from a Hirst-type sampler. These perform significantly better than using a simple particle size-filtered proxy or a Positive Matrix Factorisation (PMF) source apportionment pollen proxy. Twelve NN and RF models were developed to construct a pollen proxy, each varying by model type, input features and target variable. The results show that such models can construct useful information on pollen from OPC data. The best metrics achieved (Spearman correlation coefficient = 0.85, coefficient of determination = 0.67) were for the NN model constructing a Poaceae (grass) pollen proxy, based on particle size information, temperature, and relative humidity. Ability to distinguish high pollen events was evaluated using F1 Scores, a score reflecting the fraction of true positives with respect to false positives and false negatives, with promising results (F1 ≤ 0.83). Model-constructed proxies demonstrated the ability to follow monthly and diurnal trends in pollen. We discuss the suitability of OPCs for monitoring pollen and offer advice for future progress. We demonstrate an attractive alternative for automated pollen monitoring that could provide valuable and timely information to the benefit of pollen allergy sufferers.

Coexistence of savanna and rainforest on the ice-age Sunda Shelf revealed by pollen records from southern South China Sea

Exposure of the presently submerged continental shelf of Southeast Asia during low sea-level stands of the Quaternary is thought to be deeply involved in the biogeographic evolution of this biodiversity hotspot. Inland proxy records are mounting to argue grassland expansions over Southeast Asia during glacial periods, lending supports to the existence of a transequatorial “savanna corridor” as hypothesized. However, pollen records retrieved from marine sediments have indicated widespread rainforests on the exposed northern Sunda Shelf. To reconcile these seemingly conflicting observations, here we present new, multisite marine pollen records from the southern South China Sea focusing on the Last Glacial Maximum (LGM) time interval. It is found that the sites in front of the Sunda Shelf palaeo-rivers contain substantially more Poaceae pollen, in particular a smaller size fraction, than the site offshore North Borneo. Among the sites, abundant lowland tree pollen with similar major taxa is also observed. The co-occurrence of grass and rainforest pollen suggests a longitudinal climate gradient with increasing aridity toward the interior of glacial Sundaland. Combining our results with various palynological evidence from marine sediments seems to indicate that the vegetation on the exposed Sunda Shelf might not be fully recognized by previous studies. This is likely due to an admixture of pollen from other source regions, particularly Borneo where the rainforest was retained during glacial periods. Therefore, the extant vegetation records, from both terrestrial and marine archives, support the hypothesis of a “savanna corridor” over the LGM sundaland.

Determining if honey bees (Apis mellifera) collect pollen from anemophilous plants in the UK

Whether insect pollinators use wind-pollinated plants have implications for insect monitoring and conservation strategies in a wide range of environments. Habitats, such as coniferous plantations and arable crops of the Poaceae family are not typically considered priority for the monitoring of insect pollinators or habitat enhancement. Further many pollinator monitoring techniques focus on flowers and do not count insect interactions with wind-pollinated plants. Using two honey bee colonies from distinct environments (urban and rural) in north east England, we investigate the use of wind-pollinated plants over the summer of 2021. We combine honey bee pollen pellet analysis with airborne pollen sampling to investigate whether honey bees use three common wind-pollinated plant groups (Pinus sp., Plantago sp. and Poaceae) that have previously been considered sources of forage. Our results show that honey bees do forage on Plantago and Poaceae pollen, in line with previous studies. However, we show statistically that Pinus pollen is contamination from the atmosphere and not actively collected. It is important to consider airborne contamination before making interpretations based on small amounts of pollen in samples of bee products. The use of members of the Poaceae has implications for insect pollinator monitoring in urban environments, which has not always been considered in past studies.

Combined synoptic and regional weather patterns affecting atmospheric Poaceae pollen concentrations in Sydney, Australia

Inhalation of grass pollen can result in acute exacerbation of asthma, prompting questions about how grass pollen reaches metropolitan areas. We establish typical atmospheric Poaceae (grass) pollen concentrations recorded at two pollen samplers within the Sydney basin in eastern Australia and analyse their correlation with each other and meteorological variables. We determine the effect of synoptic and regional airflow on Poaceae pollen transport during a period of extreme (≥ 100 grains m−3 air) concentration and characterise the meteorology. Finally, we tested the hypothesis that most Poaceae pollen captured by the pollen samplers originated from local sources. Fifteen months of daily pollen data, three days of hourly atmospheric Poaceae pollen concentrations and fifteen months of hourly meteorology from two locations within the Sydney basin were used. Weather Research Forecasting (WRF), Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) modelling and conditional bivariate probability functions (CBPF) were used to assess Poaceae pollen transport. Most Poaceae pollen collected was estimated to be from local sources under low wind speeds. Extreme daily Poaceae pollen concentrations were rare, and there was no strong evidence to support long-distance Poaceae pollen transport into the Sydney basin or across the greater Sydney metropolitan area. Daily average pollen concentrations mask sudden increases in atmospheric Poaceae pollen, which may put a significant and sudden strain on the healthcare system. Mapping of Poaceae pollen sources within Sydney and accurate prediction of pollen concentrations are the first steps to an advanced warning system necessary to pre-empt the healthcare resources needed during pollen season.

Is Poaceae pollen size a useful proxy in palaeoecological studies? New insights from a Poaceae pollen morphological study in the Amazon

Poaceae (the grass family) is highly diverse, geographically widespread, and an important component of many terrestrial ecosystems. Poaceae pollen size has previously been suggested as a proxy to reconstruct the past vegetation and climates in the Amazon area, but it is still unclear if this variable can be used at broader spatial and deep-time scales. Here we set out to perform a comprehensive assessment and to test the robustness of this proxy. We generated pollen size data, as well as associated measurements of the pollen wall and pore, using 127 plant specimens from 58 species across the Poaceae phylogeny from the Amazon drainage basin (ADB). We tested the relationship between pollen size and a range of abiotic and biotic variables (vegetation type, soil composition, climate conditions, photosynthetic pathway and genome size), and fitted models using phylogenetic generalized least squares (P-GLS) and linear mixed models (LMM). Our measurement data shows that Poaceae pollen size presents a very wide range (18.77–71.62 μm), and varies not only among genera and species but also within species. There is no obvious relationship between pollen size and the explanatory variables considered here. We suggest that pollen size cannot be used as generally applicable proxy to reconstruct past vegetation and climate.