Lichenometric curves for the Polish part of the Karkonosze and Tatra Mountains established with a new method
published: Mar 1, 2015
The hitherto existing growth curves for Rhizocarpon lichens for Polish mountains were prepared in a traditional way for given climatic zones. Each altitude interval determined by vegetation-climatic zones has got a specific lichen factor. Since the rate of thallus growth changes with altitude gradually, rather than in a step-like manner, there is a problem which lichen factor should be selected when dating objects with a large vertical extent, such as debris flows. If a debris flow extends into two climatic zones and has been re-modelled many times, it is difficult to properly date successive geomorphological events because lichen factors show the rate of thallus growth most precisely for the middle parts of the climatic zones. The farther from the middle part of the zone, the less precise the dating is. Another problem, causing dating errors, is how to determine growth curves for the averaged maximum diameter thalli. This was the reason to establish new growth curves for the Polish parts of the Tatra Mountains and the Karkonosze Mountains, which would show the rate of thallus growth with altitude in a gradual, not step-like manner. This way more accurate dating of some events was obtained. The new method can be broadly used for lichenometric dating in different mountain areas. The new lichenometric curves show the relationship between lichen factor and altitude. Weaknesses of the new curve include a possibility of the increase in dating error while dating objects older than 100 years. The oldest mark objects in the Polish part of the Karkonosze and the Tatra Mountains are only a hundred and a few years old so even using traditional curves, the dating may be inaccurate.