Differential trait responses of Phragmites australis to urbanisation

The littoral zones of shallow lakes are critical transitional habitats and emergent macrophytes, such as common reed ( Phragmites australis ), frequently dominate these margins. The potential effects of urbanisation on the common reed in the littoral zone of Lake Balaton were investigated. Elevated artificial night light levels were detected along the shoreline, reflecting extensive human activity, with littoral zones exhibiting significantly higher illumination than pelagic areas. No statistically significant correlations were observed between artificial night light and most vegetative parameters, while reproductive biomass and the proportion of flowering individuals were found to be significantly negatively correlated with it. Furthermore, a statistically significant positive correlation was identified between artificial night light and the timing of the start of the season, indicating a delayed initiation of seasonal growth in more urbanised sites. The findings reveal that urbanisation does not uniformly impair plant performance but acts as a complex environmental filter, shaping specific functional traits. Generative traits and the onset of seasonal growth appear more sensitive to urban pressures compared to vegetative growth, also emphasising the importance of integrating indicators for a more holistic assessment of urban impacts on aquatic vegetation.