The effects of atmospheric nitrogen deposition and soil chemistry on the nutritional status of Pseudotsuga menziesii, Pinus nigra and Pinus sylvestris

The ammonium content and the base cation content, expressed relative to ammonium, are enhanced in the soil of Dutch forests, due to the extremely high deposition of ammonium to the forest floor. A nation-wide investigation was carried out to establish whether and how these changed nitrogen fluxes in deposition and soil affect the nutritional status of coniferous trees. The chemical composition of needles of Douglas fir, Scots pine and Corsican pine showed a regional trend similar to that of deposition and soil solution. Particularly nutrients, expressed relative to nitrogen, decreased from North to South. Of the macronutrients phosphorus was most often deficient and therefore probably limiting in the Douglas fir stands. Many pine trees suffered from relative magnesium shortages. In all stands, magnesium and, in Douglas stands, also phosphorus contents of the needles were negatively correlated with ammonium and ammonium/cation ratios in deposition. However, in contrast to pine trees, nutrient contents in needles of Douglas fir showed correlation with nitrate rather than with ammonium in the soil solution. Correlation analyses indicate that nitrogen fluxes in the soil, indirectly affect the nutritional status of coniferous trees.