Atmospheric deposition to forest ecosystems

Atmospheric deposition is an important source of macro- and micronutrients to forest ecosystems (Parker, 1983). This input to the nutrient cycle can be a deterministic factor for tree growth and forest health. On the other hand, a large input of nutrients in the form of inorganic nitrogen (N) may result in eutrophication of surface waters and terrestrial ecosystems. Also, atmospheric deposition of high amounts of acidifying air pollutants (sulfur, S, and N) may lead to acidification of both forest soils and surface waters. In the past decades, atmospheric deposition to the majority of European forests has been dominated by long-range air pollution, for example, through sulfur dioxide (SO2), nitrogen oxides (NOx), and ammonia (NH3) emissions from fuel combustion, industrial, and agricultural processes which increased from the 1950s until the 1980s and 1990s but now seem to have decreased again in Europe. Knowledge on atmospheric deposition to forests is important for studies of air, water, and soil quality. Deposition monitoring can help clarify trends in atmospheric deposition through the years in order to assess whether emission patterns have an effect on deposition. As such, deposition monitoring is an important input to the creation and implementation of clean air policies at the European level. Long data series of atmospheric deposition are also useful in nutrient cycling research as well as in extended acidification and eutrophication modeling research. This chapter describes and discusses appropriate measurement and estimation methods for atmospheric deposition to forest ecosystems and presents some results obtained within the European approach of the International Co-operative Programme (ICP Forests).