Response of the lichen Cladonia rei Schaer. to strong heavy metal contamination of the substrate.

The phenomenon of mass occurrence of the lichen Cladonia rei in extremely contaminated post-smelting slag dumps was studied in relation to metal accumulation capacity of this lichen. The research was aimed to evaluate the relationships between element contents in the thalli and in the corresponding substrate. The study was conducted in terms of a wide spectrum of Zn, Cd, Pb and As contents. The concentrations of these elements in the lichen thalli and substrate samples were measured. Various regression models were considered to find the best fitted one that greatly reflects the dependencies. Various Cladonia species and the hyperaccumulator Diploschistes muscorum were also included in the study for comparison purposes. Specific non-linear regression models described by a power function reflected relationships between Zn and Cd contents in C. rei thalli and in the host substrate in the most reliable way. The relationship for As was also noted, but none significant model was found. Contrarily, Pb concentrations in the thalli varied independently of the metal levels in the substrate. Nevertheless, the concentrations of all measured heavy metals in C. rei thalli are relatively low considering the frequently enormous substrate contamination. Different Cladonia species demonstrated a generally similar accumulation capacity and could be considered as weak accumulators. The restrained accumulation pattern may be one of the important attributes of C. rei which facilitates its colonisation of extremely contaminated dumps. This finding highlights ecological importance of this species as stable and resistant pioneer in such affected sites.