The highest defoliation in Estonia has continually been assessed in Scots pine though a permanent improvement of crown conditions of the trees has been observed since 1992. In 1996-99 there was a slight increase in the defoliation of Norway spruce and the steady decrease in defoliation, observed in 1989-95 stopped. The decrease in the defoliation of the Norway spruce is more noticeable in north-western and northern Estonia. Only 9.4 per cent of the Norway spruces and 8.9 per cent of the Scots pines were defoliated more than 25 per cent in 1999. The age of trees seems to have a great impact on both defoliation and discoloration of Norway spruce. Defoliation of older Norway spruces is higher than that of younger ones. Only 37 per cent of the older trees were defoliated less than 11.5 per cent and the proportion of such trees has decreased over the last four years. From Norway spruces younger than 60 years as many as 86 per cent of the trees were defoliated less than 11 per cent. In 27 sample points the Norway spruces had secondary shoots, in 16 points the proportion of the trees with secondary shoots was 10 per cent in 1999. In total the health state of the deciduous trees was markedly better than that of the conifers. For example, the share of healthy birches was 96 per cent in 1999

Virumaa has the richest forest resources in Estonia. The area covered with forests in Virumaa amounts to 51.3 per cent (total in Estonia 49 per cent). Pine, birch and spruce forests dominate. A large part of forests are under technogenous pressure (oil-shale mining, power engineering etc.). The total amount of all the fellings in 1999 was 1.061 million cubic metres (in Estonia totally 6.704 mln. cubic metres). The volume of fellings has reached the critical level close to the annual increment of forests. Therefore, the volume of cutting down forests should not be increased

The paper is based on the data of geochemical mapping of the humus horizon of soil and geochemical monitoring of soil carried out in 1986-94. These data have been supplemented with results of later investigations. The authors describe the formation of parent rock of soil in NE Estonia and its major geochemical features. The main plant nutrient elements and those having a negative influence of plant growth and the development of animate nature in the case of their elevated concentration in soil are observed. Components are areal distribution of technogenous atmospheric pollution falling on the ground surface in NE Estonia are also dealt with. The chemical composition of the humus horizon of soil in NE Estonia is variable, the variation coefficient of several elements exceeding 100 per cent. The trends of lateral changes in the concentration of elements are accidental. Such heterogeneity is mainly due to great variability of parent rocks of soil. Glacial deposits formed from Proterozoic crystalline rocks of Fennoscandian origin, as well as the Vendian and Paleozoic sedimentary rocks, among the latter mineralised or ore-bearing varieties, Dictyonema shale and phosphorite. Mean concentrations of elements in the humus horizon of NE Estonian soils are close to the respective concentrations of the whole Estonian territory, but differ considerably from the mean concentrations of all continents

The greatest sources of atmospheric emissions of alkaline dust and SO2 in Estonia are the soil shale based power plants and the cement production. In the vicinity of oil sale processing and chemical plants the organic pollutants, as well asammonia, H2S etc. are also found in the ambient air. Temporal changes in emission amounts and in atmospheric air pollution levels in North-East Estonia since 1960 until today (1997-98) are discussed. During the period of 1989-98 the emissions from power plants decreased about 2.5 times and those from cement production up to 40 times. In 1960-89 oil shale fly ash was the prevalent factor of air pollution, most notably in north-eastern and northern parts of the region. Since 1990-91 the proportion of SO2 has increased in the balance of alkaline and acidic components in some industrial areas. Zonation of landscapes on the basis of air pollution and the critical loads of pollutants for forest trees and Sphagnum are discussed

Air pollutants (oil shale fly ash, gases, organic compounds) emitted by the oil shale industry in Kohtla-Jaerve, North-East Estonia, have caused changes in the growth conditions of forest ecosystems. Compared with the period before 1990 the pollution load in the area investigated has fallen drastically; however, this has not resulted in an essential improvement in growth conditions of trees. Morphological analysis of 80-year-old Picea abies (L.) Karst. and Pinus sylvestris L. growing on sample plots (6) in the polluted area and in the control area showed that air pollution has had a temporally and spatially variable effect on the parameters characterising the state of trees: length growth, weight and dry matter content needles and shoots, density of needles on shoots and radial increment of trees. The length growth of Scots pine needles and shoots proved to be one most suitable parameters indicating the influence of air pollution, although not in all sample plots investigated. The results for fresh and dry weight of needles revealed great differences between sample plots. The biomass of the shoots of Norway spruce was notably greater in the immediate vicinity of Kohtla-Jaerve than in the control. The Scots pines and Norway spruces whose shoots showed inhibited length growth had greater density of needles on shoots with difference from the control being respectively up to 33 per cent and 16 per cent. The effect on the radial increment of Norway spruces was especially strong in the immediate vicinity of pollution sources but it fell rapidly with distance from them

In 1985-99 studies were carried out in the area of the Kunda cement plant on North Estonian coastal plain on sample plots stretching 1.5 and 2.5 km east and 2 km and 3 km west, where changes in crown damages and radial increment of pine and spruce were estimated. The selected stands were with 0.7-0.8 density and II quality class, with moderately dense or sprase understorey, 75-85-year-old Myrtillus site type pine or spruce stands. Practically every tree in the area of intensive dust pollution had signs of damage. The relations between the defoliation and radial increment in the region were not linear. Weak defoliation (up to 25 per cent) influences slightly the radial growth. The correlations were more evident on Pinus sylvestris with more than half of the trees in the area having moderate or strong defoliation (at least 30-35 per cent). We suppose that defoliation, which leads to a decrease in the assimilating area of trees, causes essential changes in physiological processes. In the region of intensive pollution stress the radial increment decreased along with the defoliation level on both Pinus sylvestris and Picea abies

To study the impact of air pollution on the growth of conifers sample plots were established at different distances and directions from the Kunda cement plant. The plots included stands of 70-80-year-old Scots pine and Norway spruce. Although emission of alkaline cement dust had decreased in the second half of the 1990s analyses of soil samples collected to characterise the growth substrate of trees showed that the pH value of the humus horizon of weakly podzolised temporarily overmoist sandy soils was within the radius of 3 km from the cement plant 2.0-2.9 times as high as that of the control plots in Lahemaa National Park. To ascertain the effect of alkaline environment on the growth of conifers the length (cm) of the needles and shoots formed in 1996-99, dry and wet mass (g) of 100 needles, dry matter content of needles(per cent) and density of needles on shoots were measured. The results obtained were compared with data from 1992 if possible. Both pine and spruce were found to be sensitive towards cement dust pollution and alkalised environment; however, the impact on different morphological parameters was different. As compared to the control, the strongest inhibition of growth was revealed in the sample plot situated 2.5 km east from the cement plant. Conifers on sample plots 2 km west from the emission source showed more vigorous growth than the control. As compared with data from 1992, some improvement in the growth of pine and spruce was observed

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)

The present paper is based on experiments carried out with black spruce in the industrial area North-East Estonia. Two-year-old seedlings of black spruce were planted in a sample plot affected by a cement plant and by oil-shale processing enterprises and in an unpolluted control sample plot in 1990. At the end of the experiment in 1997 it was ascertained that the impact of industrial alkaline air pollution complexes resulting in the alkalisation and chemical deviations of growth conditions retards the height growth of trees and brings about a decrease in their biomass. The sturdiness quotient was higher and the Dickson quality index was lower than the control, indicating serious damages of trees under air pollution. Increasing share of needles in the total biomass in polluted areas in comparison with control trees suggest that compensation mechanism were started in trees to increase the assimilating mass in order to survive under stress. The state of young black spruces in alkalised industrial areas shows unsuitability of using this species in industrial areas