The effect of alkaline air pollutants appears on 98% of the area of forests in Slovakia. Despite a local impact of magnesite air pollutant type is very significant as to the degree and extent of damage. Despite enormous efforts of magnesite plants only a low reduction of dust fallout was reached. While in the years 1978-1979 emission of Mg dust reached 7396.5 tons and emission of SO2 1133.5 tons, in the years 1990-1991 respective figures were 1174.5 tons of Mg dust and 1114 tons of SO2. It means that the amount of emitted SO2 has not changed but the amount of emitted dust has dropped 6.5 times. On the basis of research results the whole attacked territory was divided into four zones of endangerment and there were tested various reclamation and revitalization measures successfully

The alkalinization has a positive influence on soil microflora abundance. The number of ammonifiers nearby the plant is greater by 2-4 times than in relatively unpolluted soils of the same type, while the amount of denitrifiers and anaerobic nitrogen-fixing microorganisms even by 20-50 times. Alkalinization has induced biological soil activity. The data obtained are compared with the data of analogous studies conducted on forest ecosystems affected by acidifying pollutants

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

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