Changes in the epiphytic lichen biota of Białowieża Primeval Forest are not explained by climate warming

Epiphytic lichens are sensitive bioindicators responding to climate change and atmospheric pollutants. Climate warming changes in lichen biota have been reported from Western and Central Europe; therefore, similar trends in the biota of the close-to-natural forests of Eastern Europe were expected. In both examinations (1987–1989 and 2015–2016) of 144 permanent plots the same field method was used. The following functional epiphyte groups were distinguished: climate warming indicators (VDI species and species containing Trentepohlia algae) and Wirth's ecological indicators (T – temperature, N – eutrophication, R – reaction, M – moisture). PCA ordination for exploring species composition changes, species richness and diversity (Shannon-Wiener index) in different forest types was used. When compared with the earlier survey, a higher plot species richness, Shannon-Wiener diversity index, and proportion of more nitrogen-demanding lichens, and lower proportions of warm-demanding and high-acidity tolerant lichens were found. No change in the epiphyte biota composition influenced by the decreasing atmospheric precipitation was detected. The species richness and Shannon-Wiener index of climate warming indicators did not show a significant change. Although the share and frequency of epiphytic lichen species and their functional groups changed over a 25-year period, no relationship was found to be related to climate warming: indicators of global warming showed no significant change in frequency, while those with higher value of T even decreased frequency. The changes suggest a connection with eutrophication (increase in frequency of species with higher value of N) and a decrease in sulphur deposition (increase in frequency of species with higher value of R).