Flowering Phenology of Selected Grass Species in Connection with Grass Pollen Dynamics

Most of the environments on Earth are occupied by life. The atmospheric environment might seem void of life but it is occupied by many bioaerosols such as bacteria, viruses, plant pollen, fungal spores, arthropods and more. Many of these bioaerosols have negative health impacts on human societies through the allergenicity of the components of their cells.
Perhaps the most allergenic group of bioaerosols are grass pollen. They have been linked with major loss of productivity and quality of life for the grass pollen allergy sufferers. Grass pollen originate from flowering grasses, with differential contribution depending on plant abundance, species biodiversity, pollen production and other biological and environmental factors. Sources and sinks of grass pollen have been identified and quantified, but the connections between sources and sinks are uncertain. The details behind these connections are found in the mechanisms of plant phenology, pollen release and pollen deposition.
To investigate these connections a multidisciplinary research ethos from botany, ecology, environmental and atmospheric sciences, laboratory-based molecular biology, and statistical mathematics was utilized to gain a comprehensive and multispectral view of grass flowering and grass pollen dynamics. Pollen monitoring, atmospheric modelling, flowering phenology, eDNA and metabarcoding were all combined to investigate these connections.
Grass vegetation source areas within the larger Midlands area were important in contributing grass pollen to the Worcester sampling sites. Areas further than 30 km did not contribute significant amount of pollen. Spatially homogeneous stochastic and demographic elements were isolated from detailed observations of eight populations of flowering Dactylis glomerata found throughout the larger Worcester region. These elements were utilized to model pollen release scenarios. These scenarios were further confirmed to be representative of atmospheric pollen levels using species-specific eDNA samples that had been processed using DNA metabarcoding and bioinformatics. An isolated population of Festuca rubra were shown to contribute only minor levels of pollen eDNA to samplers located 300m away, highlighting the heterogeneity of dispersion distance from pollen source areas to the local environment.
The connection between atmospheric eDNA and flowering phenology have previously been one of the major missing link in current aerobiological knowledge. These findings have contributed new understanding that will be essential in the mechanistic modelling and forecasting of pollen dynamics and to solve the underlying connection with phenology.