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 sylvatica. Soil water monitoring revealed an overall decrease of ion concentrations and an annual peak in September due to seasonal nitrification. Liming reduced 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 SO₄ ^2-, which prevented a rise of pH, except during nitrification peaks. Liming had no effect on height increment of Fagus but stimulated Acer, which suffered 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-demanding species expanded while species that tolerate nutrient-poor conditions 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.