@phdthesis{Ranpal2024, author = {Ranpal, Surendra}, title = {Impacts of environmental factors on pollen production of birch across different climatic conditions in Europe}, doi = {10.17904/ku.opus-963}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:824-opus4-9637}, school = {Katholische Universit{\"a}t Eichst{\"a}tt-Ingolstadt}, pages = {18 ungez{\"a}hlte Seiten, 114 Seiten : Illustrationen, Diagramme, Karten}, year = {2024}, abstract = {Pollen production in birch trees (Betula spp.) is a crucial factor influencing plant reproduction and public health, as birch pollen is a major aeroallergen. However, the complex interactions between environmental factors and birch pollen production are not fully understood. This doctoral thesis aims to investigate the impacts of genetic, climatic, and other environmental drivers on pollen production across different birch species and climatic conditions in Europe. The research therefore gains major importance since climate change conditions are believed to alter the risk and severity of allergic diseases and may change conditions for reproduction in forest tree species. The major questions addressed in this PhD thesis are: 1. What are the pollen production estimates for Betula species? In other words, how many inflorescences and pollen are produced by distinct types of the tree species? 2. Is there a year-to-year variation in birch pollen production? 3. How do genetic and environmental factors influence birch pollen production at local and regional scales? The research presented in this thesis is based on three peer-reviewed publications that employed a multi-faceted approach to address the overarching research questions. The first study (Chapter 4) assessed pollen production in cloned individuals of weeping birch (Betula pendula) over three consecutive years (2019-2021) in a seed plantation in Germany, with catkin samples collected from 28 birch trees. The second study (Chapter 5) investigated pollen production of downy birch (Betula pubescens) along an altitudinal gradient of 522 meters in the European Alps during 2020 and 2021, with catkin samples collected from 17 birch individuals at nine different altitudinal locations. The third study (Chapter 6) evaluated the continental-scale impacts of meteorology (temperature, precipitation) and atmospheric gases (ozone, carbon dioxide) on downy birch pollen production across 37 International Phenological Gardens (IPGs) in Europe, with catkin samples collected over three consecutive years (2019-2021) and tree age was approximated by stem circumference. We adopted a standardized method to extract pollen from catkins and maintained methodological consistency across all three studies. For Chapter 4 and Chapter 5, environmental factors such as air temperature, air quality, and solar radiation were monitored at the study sites. For Chapter 6, high-resolution (0.1°) gridded meteorological data were obtained from the E-OBS dataset, and concentrations of O3, NO2 and CO2 were derived from Copernicus Atmosphere Monitoring Service (CAMS) reanalysis. The major statistical analyses included non-parametric tests such as the Kruskal-Wallis test, Mann-Whitney U test, Spearman's correlation, and mean regression. Additionally, the research incorporated a distribution-free quantile regression method, where the quantiles of the response distribution (pollen production) were modeled directly. This allowed for assessing the impacts of factors such as temperature and O3 levels across different quantiles of the response variable. All statistical analyses were carried out using R versions 4.1.2, 4.2.2, and 4.3.2. We estimated mean pollen production for two birch species: 1.66 million pollen grains per catkin for B. pendula (Chapter 4) and between 0.4 and 8.3 million pollen grains per catkin for B. pubescens (Chapter 5 and Chapter 6). Moreover, significant annual fluctuations were noted in both pollen and catkin production. Our findings also include indication of masting behaviour in the selected birch trees (Chapter 4 and Chapter 5), suggesting that annual variations in pollen production could be influenced by masting, which may mask the effects of environmental factors such as temperature. At the seed plantation site, we observed that genetic variability in birch trees leads to increased variability in pollen production (Chapter 4). Consequently, to effectively investigate the effects of environmental factors, we employed a research design that minimized genetic variability among trees. This approach was applied in our study across Europe using IPG birches, which exhibit reduced genetic variability (Chapter 6). The results from studies in the European Alps (Chapter 5) and across Europe (Chapter 6) showed significant positive correlations between air temperature and pollen production in birch. However, no correlations were observed with altitude (Chapter 5) or CO2 concentration levels (Chapter 5). Increasing O3 concentration levels tended to decrease pollen production (Chapter 6). The findings suggest that further climate warming could worsen the adverse effects on individuals with pollen allergies. This doctoral research provides novel insights into the complex environmental controls on pollen production in birch species, contributing to a more detailed understanding of the potential impacts of climate change on plant reproduction and public health.}, subject = {Europa}, language = {en} }