Forty-five macrolichen species were registered on 29 forested sample plots in Laeaene- and Ida-Viru counties in North-East Estonia. Analysis of the macrolichen species distribution indicated and impact of air pollution on the epiphytic lichen cover. The presented distribution maps demonstrate that lichen species belonging to different ecological groups by substrate requirements respond differently to air pollution. Lichen species diversity was analysed by means of species richness, diferent diversity measures including the Shannon-Weaver Diversity Index, and characterised by the sum of species abundances. Alpha diversity of epiphytic macrolichens for the study area is 8.3 (s.d. 5.5), beta diversity 5.4, and the Shannon-Weaver Diversity Index varied from 0 to 1.189. Variations in the lichen community demonstrated the existence of a steep local air pollution gradient oriented from north-east to south-west

A needle trace method was used to reveal the chronology of needle retention and growth rates on Scots pine in a stand near a power plant operating on oil shale. During the period of 1964-97, the height increment varied between 31 and 64 cm yr (-1), and the radial increment ranged from 1.06 to 3.71 mm yr (-1). The average needle density on the newly sprouted shoots of the main stem was 5.9 needles cm (-1) and the mean needle production on the same shoots was 266. The average number of needle sets along the main stem ranged from 2.2 to 3.1, the mean age of needles varied between 1.3 and 2.3 years. The short-term maximum concentrations of oil shale fly ash and SO2 ranged from 55 to 2510, and from 75 to 270 micro g m (-3), respectively. The annual average concentrations of fly ash varied between 6 and 95 micro g m (-3), and of SO2 between 2.5 and 10 micro g m (-3). Changes in neither the concentrations of fly ash nor SO2 were associated with the variation in needle retention of Scots pine. In the case of height increment, however, the correlation with the annual average concentration of oil shale fly ash was significant (r=0.83; p0.05)