Differences in Tolerance of Alnus cordata (Loisel.) Duby and Tilia × europaea L. ‘Pallida’ to Environmental Stress in the First Year After Planting in Urban Conditions

The success of establishing new trees in cities and their subsequent growth depend, among others, on the proper selection of tree species which can easily tolerate the post-planting stress. In the spring of 2023, young Italian alder (Alnus cordata (Loisel.) Duby) and common lime (Tilia × europaea L. ‘Pallida’) trees were planted in a street of heavy traffic in Warsaw. In the summer of 2023, leaf samples were collected during the growing season for chlorophyll a fluorescence measurements and chemical analyses. Additionally, the autumn phenological phases were monitored. Chlorophyll a fluorescence measurements revealed higher values of Fv/Fm, density of reaction centers per cross-section, and electron transport chain efficiency between photosystems II and I, as well as lower energy dissipation rate per active reaction center of photosystem II in A. cordata. Moreover, A. cordata revealed higher chlorophyll a, chlorophyll b, and carotenoid content. The flavonoid and proline content in both species was the highest by the end of July and then decreased. In T. × europea ‘Pallida’, the contents of these stress biomarkers increased in the late growing season. Our results showed that T. × europaea ‘Pallida’ is less resistant to post-planting stress in urban conditions, while A. cordata showed higher resistance to variable weather conditions, high photosynthetic efficiency, and long foliage lifespan.