Horse Chestnut (Aesculus hippocastanum L.) Urban Habitat - Pollution Influence on Some Phenotypic and Morphological Characteristics

摘要

Background and purpose: Horse chestnut (Aesculus hippocastanum L.) may be found in most urban areas in Croatia. Over the years it showed to be resistant to various negative urban influences. In this research we tested trees on randomly selected streets with intense traffic in smaller towns. The main goal of this research was to establish the link between pollution and tree growth and to analyze to what extent pollution influences the increase in the measured parameters. Materials and methods: The research was done in 7 settlements, in towns with the population of up to 75 000 inhabitants. The measured parameters were the morphological characteristics of trees, shoots, leaves and nuts. From the selected branches we measured the annual shoot (thickness and length), leaves, the number of flowers and nuts. The crown transparency was assessed according to the ICP Forest method. Results and conclusions: The phenotype of the urban Horse chestnut significantly differs from its natural phenotype, and it is transformed by multiple radical pruning, what may be seen in the following ratios: the diameter at breast height - tree height, trunk height - tree height, crown height – tree height, crown width – crown height. The most significant characteristic of the tree is the vitality expressed by crown-damage classes. On the selected trees the worst crown damage class was “3b” and the best was “0”. The measured parameters of yearly shoot characteristics were defined. All measured parameters (trees, shoots, leafs and nuts) show significant differences from thegiven average values.