The Influence of Urban Conditions on the Phenology of Aesculus hippocastanum L. Using the Example of Wroclaw (Poland)

The differences in plant phenology between rural and urban areas are the subject of research conducted all over the world. There are few studies aimed at assessing the impact of the urban heat island on plant vegetation only in urban areas. The aim of this study is to assess the impact of the distance from the city center and the form of land cover on the phenological development of trees using the example of the horse chestnut (Aesculus hippocastanum L.). The research area covered the entire city of Wrocław. In order to best capture the impact of the distance from the city center on the rate of changes of individual phenophases, 3 areas were designated—at a distance of 1 km, 2 km and 5 km. The study assessed the average duration of individual phenological phases along with the variability characteristics for leafing, flowering and fruiting in relation to the designated zones and classified forms of land cover based on mean value (x¯) and standard deviation (±SD) in individual weeks of the year. For the leafing and flowering phases, the frequency of the occurrence of phases in individual weeks of the year was analyzed in relation to the designated zones and classified land use methods. The results obtained on the basis of phenological observations carried out in 2017 in Wrocław confirmed the extension of the period of vegetation in the city center in relation to its peripheries. Trees growing in road lanes entered the vegetation period later and defoliated faster, which confirms the negative impact of street conditions on the development of trees in urban space. Thus, the growing season in road lanes is shorter and due to the 1-year observation period, it is justified to conduct further observations.