Chemical composition of throughfall,soil water,leaves and leaf litter in a beech forest receiving long term application of ammonium sulphate

Nitrogen deposition in the range of 10–40 kg N ha^-1 a^-1 is common in large parts of Europe. Substancial amounts are deposited as NH ₄ ⁺ having fertilization and acidification effects in ecosystems. In a long term experiment the reactions of different compartments of a forest ecosystem were studied when the system became N saturated by continuously applying (NH₄)₂SO₄. The experiment was conducted in a beech forest and the application of 10 kmol_c N ha^-1 a^-1 lasted 11 yr from 1983 till 1993.The results revealed that despite the high soil acidity, the applied NH ₄ ⁺ was quickly oxidized to NO ₃ ^- in the surface 10 cm soil layer and leached to deeper depths. The amount of NO ₃ ^- leached from the surface soil increased during the initial three years and remained constant on a high level for the rest of the experimental period. Nitrification was associated with acidification of the soil solution, causing high concentrations of Al and Mn²⁺ in soil solutions. More than 50% of total Al in solution occurred in non-phytotoxic form (Al–SO₄ complexes). Moreover, concentration of base cations and dissolved organic carbon increased. Concentrations of SO ₄ ^2- in soil solutions increased during the first few years approaching more or less constant values in the surface 40 cm depth, whereas in 40–100 cm depth it took about 10 yr to reach those levels of sulphate concentrations in soils, indicating its retention in the deeper soil layers. No significant change in the chemistry of throughfall water and leaves was observed, indicating to N-saturation of the trees.