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

Prolonged effects of the multicomponent air pollution complexes emitted from the cement production in Kunda and oil shale processing in Kohtla-Jaerve, North-East estonia, on the forest ecosystems are discussed. It was found that atmospheric input substantially affects biogeochemical cycling in forest. The comparatively high concentrations of alkaline dusts and ash and various gaseous pollutants in the atmosphere of the investigated areas over 40 years have caused qualitative and quantitative changes in the forest soil, soil water and precipitation and in the state of forest and trees. Although the levels of air pollutants emitted by the industry have seriously decreased in recent years, alkalisation of the growth environment of trees is still essential in some regions. Alkalisation of soil and soil water in the vicinity of Kunda and Kohtla-Jaerve complicated mineral nutrition processes and disbalanced mineral elements composition in tissues, which resulted in a decrease in the increment and quality of trees