The effects on forest growth of air pollution from energy production

The properties of the atmosphere have changed and will continue to change due to changes in anthropogenic activity. The change in the atmosphere is reflected in the functioning and growth of forests. This is analyzed by considering the changes in the amounts and flow rates of different substances in the entire system of the atmosphere, forest soil and forest trees. Possible effects are either direct or indirect. Three direct effects are treated in more detail, i.e. the effect generated by toxic compounds, increasing CO₂ and N deposition. The indirect effects are connected to the acidification of soil, i.e. the amounts of nutrients and toxic compounds in the soil.The study concerns coniferous forests on sandy soils in Finland. Generalization of the results and a forecast to the year 2040 is based on a multiplicative model based on the five components. According to the growth data in conservation stands the growth on sandy soils has increased by 30% during the period 1900–1980. Model analysis for the same period is shown to produce good agreement with the measured growth data. The increase of growth is presumed to be due to the steady increase in CO₂ and nitrate deposition. Continuing changes in the environment will affect negative changes in the forest growth by the end of the 20th century. The decrease is presumed to be due to acidification effects in the soil. The ion exchange process in the soil will generate a time lag between acid deposition and its effect. This time lag in the soil in Finland is expected to be 20 ±10 years. Effects of two other time lags are also analyzed.