The research was conducted in 1990-99 in forest observation sites in the neighbourhoods of industrial enterprises of Kohtla-Jaerve-Johvi and the cement plant of Kunda and in the control area in Lahemaa National Park. Differences between the radial increments of conifers growing under pollution and in a relatively unpolluted area were estimated. The stands selected for investigation were similar as to their edaphic conditions and forest survey indicators. The high sensitivity of conifers to long term emissions of pollutants into the atmosphere from oil shale based power engineering and chemical industry, production of building materials and fertilisers and other industrial enterprises in the investigation area is expressed as changes in the radial increment of trees with the changes depending on the pollution load and alterations in precipitation and soil

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

The aim of the study was to compare the amount of epicuticular waxes of Norway spruce and Scots pine needles from the area of cement production in Kunda. The amount of Norway spruce waxes decreased under air pollution influences and with ageing. The quantity of waxes of Scots pine needles showed an increasing tendency in the polluted area and in one-year-old needles compared with the current-year ones. A rapid decrease in the amount of waxes was established also in the older needles of Scots pine

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

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)

It was ascertained that the content of soluble sugars, starch and ratios between different forms of carbohydrates varied in the trees growing in areas affected by industrial production in Kohtla-Jaerve and Kunda. The ratio of soluble sugars to starch is a good indicator of the state of trees in industrial areas. This ratio depends on the level of air pollution. In the studied areas a strong relationship between the content of soluble sugars and N, Mg and K was observed in the needles of Norway spruce

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 influence of air pollution from a cement plant on chlorophylls and carotenoids of the needles of Scots pine and Norway spruce was studied on the sample plots established at different distances from the emission centre in 1992, 1994 and 1999. No essential difference was observed in pigment concentrations in needles between 1992, when the emission of cement dust from the plant was very high, and 1999, when dust pollution had practically stopped. The negative influence on the synthesis of pigments in needles occurred through the alkalisation of soil and disbalances of mineral nutrients accumulation into the organism

Element concentrations in the xylem wood of Scots pines (Pinus sylvestris L.) growing in different soil and pollution load conditions at Narva-Joesuu and Haeaedemeeste, Estonia, were studied for temporal trends with respect to soil properties. The upper horizons of the Haeaedemeeste stand soil profile were strongly acidic compared with those of Narva-Joesuu, which were weakly acidic. Element concentrations for K, Ca, Mg, Mn and Zn in upper soil horizons were higher at the Narva-Joesuu stand and for Pb at Haeaedemeeste. Concentrations of xylem elements Mg, K, P, Pb and Cu were higher in the Narva-Joesuu sample and of Ca, Mn and Zn in the Haeaedemeeste sample. The concentrations of xylem elements except for K, Mg and Cu were poorly associated with those in soil. The increasing concentrations of Ca, K, P and in the Narva-Joesuu sample during the last decades can be explained by the larger amounts of emissions of the oil-shale fly ash by the neighbouring thermal electric power stations. Thus, the alteration of the concentrations of these elements in the xylem offer a promise for determining deposition-mediated changes in the environment