engleski

Impact of the city of Zagreb, Croatia, on the lichen flora of Medvednica natural park: a preliminary survey using epiphytic lichens as biomonitors

Lichen flora of Croatia is still much unknown and lichens as bioindicators have not much been used here. The purpose of this paper is to present preliminary overview of impact of the city and its inhabitants, by the means of industry, tourism and forest management on the lichen flora on the natural park which presents � the lungs of the city� . Zagreb is partly situated on the south slopes of the mountain Medvednica whose largest part is under protection on the niveau of natural park. About 50 years ago only one road was going up to the top of the mountain, but since then much more have been built together with some hotels, TV towers etc. As not much lichenological work was done, the data available can only be used partially e.g. to note disappearance of certain species. Lichens were collected on various sites on the mountain and in the northern area of the city. They were then analysed by scales of toxitolerance and preferred bark characteristics (pH and nutrients). This paper shows the increase of nitrophilous lichen species especially by the roads, on the basis of the trees and more in the urban area. Checking the rose of the winds for Zagreb and the mountain shows that not much of the pollution from the city can be transmitted to the mountain but probably more pollutants come with higher air currents from the central Europe. It was noted that members of the Lobarion alliance disappeared from the mountain. Due to the fact that the levels of SO2 are decreasing since 1970� s and those lichens were noticed on the mountain even some 20 years ago, it is suggested that these lichens are extinct due to the wrong forest management, e.g. cutting down old trees and planting pure stands of the tree species that naturally don� t grow in the area, ruining the old-forest integrity. In that period it was also noted disappearance of before very abundant Usneas which are now slowly returning to the area, even found in some urban sites which supports the idea previously stated. In general, it can be stated that the air quality in Zagreb and on Medvednica is approving: the SO2 levels have dropped which can be noticed by reappearance of sensitive species, but nitrogen compounds became more important pollutant, however it is expressed mostly locally by the roads and on the basis of the trees. Better air quality is shown by reappearance of some sensitive species like Usneas. Disappearance of the members of Lobarion alliance is therefore caused by forest management and should be suggested to put some lichens on the red-list. For more detailed study it is suggested to make permanent sites for observations in the lichen flora changes but also to measure element contents and pH of the tree bark lichens are growing on.

epiphytic lichens; bioindication; Medvednica

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