Influence of meteorological conditions and climate on pollen season of the early-flowering woody taxa in Poland, Central Europe

The aim of this study is to analyse the spatial and temporal variability of the pollen seasons in Poland and to demonstrate the impact of meteorological parameters on the course of the pollen seasons within the context of climate change over two decades 2003-2012 and 2013-2022. Five early-flowering plant taxa were selected for analysis: Alnus (alder), Corylus (hazel), Populus (poplar), Ulmus (elm), and Salix (willow). Daily airborne pollen data were collected using a Hirst-type pollen trap in six cities across Poland, representing different climatic conditions. Firstly, long-term air temperature trends were analysed to identify spatial and temporal climate variability. Secondly, the differences in pollen seasons between stations were compared to assess the spatial variation. Thirdly, pre-season meteorological influences on season onset and intensity were analysed. Finally, the influence of meteorological parameters on daily pollen grain concentration in the atmosphere was examined. The results show that, in the second decade, the strongest temperature increases occurred in early-year months, potentially influencing early-flowering taxa. Over a 20-year period, the period with the highest pollen grain concentration starts earlier and lasts longer for most stations and taxa. Meteorological influences on pollen dynamics shifted over time, leading to spatial, temporal, and species-specific variation across Poland. Air temperature, insolation time, and relative humidity notably influence daily pollen levels, especially for Populus, Salix, and Ulmus (correlation > 0.2), while Corylus and Alnus show weaker correlations (< 0.1). The analysis indicates a decline in correlation coefficient values over the study period, particularly for Corylus and Alnus.