Soil water chemistry and revegetation of a limed clearcut in a nitrogen saturated forest

A clearcut stand of Pinus sylvestris in Flanders (Belgium) was limed with 3 ton/ha dolomite and reforested with Acer pseudoplatanus and Fagus sylvatic a. Soil water monitoring revealed an overall decrease of ion concentrations and an annual peak in September due to seasonal nitrification. Liming redu ced concentrations of NO3- and Al3+ and raised concentrations of K+ and Mg2 + and the molar ratio of(Ca+Mg)/Al. Liming also stimulated release of SO42- which prevented a rise of pH, except during nitrification peaks. Liming ha d no effect on height increment of Fagus but stimulated Acer, which suffere d from severe deficiencies of calcium (Ca), magnesium (Mg), potassium (K), and phosphorus (P) without treatment. Nitrogen (N) was not growth-limiting for Fagus or Acer and liming had no effect on N concentrations in leaves of both species. Liming had a strong impact on ground vegetation. Nutrient-de manding species expanded while species that tolerate nutrient-poor conditio ns decreased. It is argued that changes in ground vegetation had a greater impact on reduction of NO3- concentration in soil water than increased tree growth.