The effects of acid irrigation and compensative liming on soil and trees in a mature norway spruce stand (Hoeglwald Project) : Waldschadensforschung - Wissensstand und Perspektiven. Internationaler Kongress

1990

S. 667-690

13 Abb., 11 Lit. Ang.

Unselbständiges Werk

200073966

Since 1984 the soil of an around 80 years old spruce stand (Picea abies L. Karst.) was irrigated with acidified water (pH 2.7 - 2.8 by H2SO4 resp. pH 5 - 5.5 by H2CO3) in 15 to 18 events a 10 - 12 mm per year additionally to natural rain of 500 to 700 mm below canopy with pH mostly between 4.5 - 5.2. The main part of the added acidity was buffered in the mineral top soil by reactions releasing Al(H2O)6 3+. A small part was consumed in the surface humus layer by exchange of Ca, Mg, Mn and K. Up to now the trees do not show any signs of growth reductions, needle losses or discolourations. It seems that defensive mechanisms in the fine root system are responsible for that as active raise of pH on the rhizoplane of fine roots, possibly due to nitrate uptake. Liming, carried out once in April 1984 with 4.103 kg ground dolomite per ha, produced a strong increase of the pH only in the upper part of the humus layer, forming a steep pH gradient by depth. That gradient marking the deacidifation front is moving downward very slowly with time (around 1 cm/year). Although nitrification was already very active before lime was brought out liming enhanced the nitrte production markedly. At a depth of 20 cm the nitrate concentrations reached 280 mg/1 in the soil solution. Liming also enhanced the release of water soluble humic substances. Because of their ability to form stable organic complexes with Fe, Cu, Pb and Al, the contents of these metals increased in the soil solutions.