In a period of 12 weeks, samples of white poplar bark (Populus alba), naturally covered with lichens of the Xanthoria parietina and Physcia aipolia species, and were polluted under lab conditions with different levels of Zn and Pb. The pollution was done through the watering and nourishing solutions and the level of the two pollutants varied between 20 – 240 mg Zn/L and 10-120 mg Pb/L. The reaction and adaptation mode of the two lichen species was assessed through the phytomass abundance study, evaluated according to the bark surface covering degree. The watering performed to pollute and nourish was done twice a week. Measuring the surface covering degree was done through planimetry at 3, 6, 9, and 12 weeks. Our results evidenced great sensitivity of the Physcia aipolia species to high pollution levels of Pb and ZN. The covering degree is reduced after 3 weeks to 60%, to 95% after 6 weeks, and at 9 weeks, this species completely disappeared. After an accommodation period of about 3-4 weeks, when the covered area remained the same, the covering degree of the surface by the Xanthoria parietina species increases by 10% at 6 weeks, reaching 15% at 12 weeks. These results lead to the idea that the careful study of the lichen abundance may offer in an easy way signal-news about the gaseous pollution level of the environment.

corticolous lichens; high levels of Pb and Zn; lichen abundance; monitoring

Presentation: oral