THE EXMAN PROJECT - BIOGEOCHEMICAL FLUXES IN PLANTATION FORESTS ON ACID SOILS

As a basis for experimentation, inputs and outputs of biogeochemicals were observed in coniferous stands in Denmark, the Netherlands, German y and Ireland. The range of deposition observed is characteristic of p opulated regions of northwest Europe, from only moderately polluted At lantic areas through decreasing marine influence and increasing deposi tion of anthropogenic nitrogen and sulphur. In intensive agricultural regions, ammonium inputs are high enough to cause nitrogen saturation of ecosystems, and nitrification acidification is a major soil process . Co-deposition of ammonia and sulphur dioxide may be significantly in creasing loads of N and S in forests in the region. Input-outputs are balanced for seasalts in the maritime sites, and sulphur outputs from the rooting zone also reflect the inputs to a large degree on these si tes. Mobilisation of cations, notably aluminium, apparently occurs as a result of acidity generated by nitrogen transformations.