Problems and possibilities of lichenometric dating in Polish mountains

The paper presents problems faced when using a new method for defining the growth curves of the thalli of the rockylichen Rhizocarpon spp in the Polish section of the Tatra and Karkonosze Mountains. Lichenometric curves based onpre-existing data were defined for two climatic-vegetation zones in the Tatra Mountains. These were mainly representativeof substrates located in the central parts of these zones. In the new lichenometric curve which was constructed forthe Tatra and Karkonosze Mts., the thallus growth curve for the first 100 years was defined in a linear manner in relationto altitude. Therefore the curve can be easily used for dating items located in any part of the altitude zone for which thecurve was defined. The paper also tackles the problem regarding the number of thalli that should be assessed when dating. An approach which assesses a certain number of the largest thalli of a similar diameter seems to be the most suitable for small-scale landforms (with small numbers of thalli) which were formed during one event. The shape of the thallus growth curve is strongly influenced by the landforms (either convex or concave) and the vertical extent of the zone in which the measurement is performed. The presence of multiannual snow patches in close proximity and air pollution also influence thallus growth on the mountains investigated. The geomorphic processes taking place turned out to be a significant problem for proper dating of the items - depending on their interpretation they can either help dating or obscure the reconstruction of the event.