EFFECTS OF A DECREASE IN ATMOSPHERIC DEPOSITION OF NITROGEN AND SULFUR ON THE MINERAL BALANCE AND VITALITY OF A SCOTS PINE STAND IN THE NETHERLANDS

Atmospheric deposition of sulphur and nitrogen was reduced to pre-industrial levels in a 45-year-old Scots pine (Pinus sylvestris) stand in the Netherlands. The reduction was achieved by throughfall interception by means of a transparent roof. In an experimental plot underneath the roof, trees were sprinkled with demineralized water to which all nutrients except for nitrogen and sulphur were added in the same amounts as present in the throughfall water. Below and outside the roof control plots were established. After 1 year of treatment the first preliminary results were available. The nitrogen and sulphur depositions were reduced from 40 to 2 and from 30 to 4 kg ha-1 year-1, respectively. The chemical composition of the soil solution showed a quick response. The sulphur, nitrate and ammonium concentrations strongly decreased in the upper soil layers. Consequently, the ratios of ammonium to potassium and magnesium also became lower. The levels of nutrients in the needles have not yet changed. However, nutrient fluxes via the litterfall have decreased slightly, which might indicate some reallocation. No changes in the undergrowth have been noticed so far.