Influence of spruce and pine on the acidity and composition of atmosphericfallout in north taiga forests of an industrially developed region

The ideas concerning the spatial and temporal variation of acidity and comp osition of atmospheric fallout in forests of the boreal zone are discussed. The role played by the atmospheric component in the functioning of these f orests depends on the acidity and composition of fallout and the extent of their transformation by the biocenosis. The most profound transformation of fallout occurs during the growing season. In spaces between crowns, the co rresponding changes are atmogenic; in undercrown areas, they are obviously biogenic (autogenic). Spruce transforms the fallout more intensively than p ine. Under conditions of industrial pollution, the atmobiogenic character o f fallout is supplemented with a technogenic component, as its acidity and concentration of pollutants and other elements sharply increase. Concentrat ions of principal cations reach high values because of their leaching from the crown by acid precipitation. The traditional concept of atmospheric loa d on boreal forests should be reconsidered taking into account their spatia l structure.