Muyshondt, Babette

Abstract: In this PhD thesis the ecology of phyllosphere bacterial communities is investigated through both observational and experimental studies. In the first part, we aimed to assess the impact of urbanization on phyllosphere bacteria communities on a broad scale, and for that we determined the composition and diversity along a fragmentation and urbanization gradient in cities across Europe. More specifically, we investigated the relationship of urban phyllosphere bacterial community composition and diversity with different urban variables including particulate matter pollution, microclimate and landscape characteristics such as green infrastructure cover in the surroundings and green area size. To do so, we sampled the phyllosphere bacterial communities of Platanus x acerifolia and Acer pseudoplatanus in 77 UGAs distributed over six European cities and determined their composition and diversity using 16S rRNA gene sequencing. In the second part, we aimed to identify and compare the seasonal variation in the bacterial composition and diversity of leaves, twigs and buds on five different tree species in identical environmental conditions. In addition, we investigated the contribution of the twig and bud phyllosphere to the leaf phyllosphere. Therefore, we followed-up the bacterial communities of five tree species in a common-garden setting, using 16S rRNA sequencing, from budburst over leaf emergence to leaf shedding from March to October. In a third part, the effect of traffic-derived air pollution exposure on the phyllosphere bacterial community is studied, either directly or indirectly via the effect of the leaf traits including leaf wettability, stomatal density and specific leaf area. Differences in air pollution exposure were created by planting Betula pendula trees along a transect at different distances from heavy-trafficked highways at four locations. To do so, we followed the phyllosphere bacterial communities and leaf traits monthly of these 58 Betula pendula trees from May to September. As a last part, we investigated the effect of ammonium fertilization and dosage on phyllosphere bacterial communities and leaf traits of Hedera hiberica plant in an controlled environment. Weekly leaf samples were collected for five weeks and one more after eight weeks. With these experiments we want to gather new and more knowledge about phyllosphere bacterial communities and their relation to urban stressors, which will be essential for their management and potential application potential in the future

An ecological perspective on phyllosphere bacterial communities in urban environments

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