Phytomonitoring study on intra urban variations of leaves of some evergreen and deciduous trees

This paper explores the hypothesis that the action of stressors changes the state of mineral content at different stages in the leaf development in urban environment, in sites close to the major traffic roads. We evaluate a low-cost method to assess urban habitat quality with relatively easy sampling and no need for complicated and expensive equipment. The method is based on quantifying gravimetric (leaf dry weight – LDW, oganic weight in leaves – LO, ash weight in leaves – LA) and physiological (leaf mineral content – LMC, leaf organic content – LOC, leaf organic content/leaf mineral content ratio – LOC/LMC, leaf mineral deposition in tissues – LTDM) parameters. These parameters are relatively simple, accurate, and inexpensive and can be quickly determined. Kruskal–Wallis tests were used in order to compare LDW, LA, LO, LMC, LOC, LTDM and LOC/LMC among the eight species (Acer platanoides, Acer pseudoplatanus, Tilia platyphyllos, Tilia tomentosa, Aesculus hippocastanum, Aesculus × carnea, Taxus baccata, Picea abies). All these species are considered as valuable forest and decorative ones recommended for planting in the green zones of the towns. These tree species are easily identified, widely distributed, and widely used in bioindication studies. The variable mineral content within leaves can be explained by environmental effects, as well as by the physiological differences between species. Species that exhibit phenotypic plasticity with respect to these parameters (Acer platanoides, Acer pseudoplatanus, Tilia platyphyllos, Tilia tomentosa) reflect changes in the urban environment. With a high mineral content, A. carnea is more suited for the urban environment than A. hippocastanum. Taking into account the existing conditions in Timisoara, we consider evergreen species (T. baccata, P. abies) to be inadequate for cultivation in areas with heavy road traffic because they show stability in leaf mineral content.