Structure and ecosystem services of small-leaved lime (Tilia cordata Mill.) and black locust (Robinia pseudoacacia L.) in urban environments

Knowledge of the structure and morphology of common urban trees is scarce, particularly of the full life cycle of a tree. The present and future structural dimensions of urban tree species are of an increasing interest because tree growth is associated with its ecosystem services. The purpose of this study was to characterize the dimensions of two urban tree species (small-leaved lime, Tilia cordata Mill. and black locust, Robinia pseudoacacia L.) and to predict future structural dimensions based on the diameter at breast height and tree age. Regression equations were developed for tree height, crown diameter, crown height, crown volume, crown projection area, and open surface area of the tree pit. The data revealed strong relationships (r2 > 0.7) between crown diameter, crown volume, crown projection area, crown height, tree pit for both species, and tree height of T. cordata. Based on tree dimensions and the leaf area index (LAI), three ecosystem services (carbon storage, shading, and cooling effects) were estimated for the analyzed trees. The results indicated that urban trees considerably improved the climate in cities, with carbon storage, shading, and cooling of single trees showing a direct relationship with LAI and age. The associations of tree growth patterns identified in this study can be used as guidelines for tree planting in cities and their ecosystem services; they may improve the management and planning of urban green areas.