Beschreibung:
AbstractThe forests of the German Solling area are heavily impacted by acidic deposition. Analysis of soil solutions derived from suction lysimeters in the field reveal strong vertical gradients of Al‐activity in the soil solution and increasing activity with soil depth. Temporal pattern of Al‐ activity in soil solutions under field conditions cannot easily be predicted by equilibrium models using Al(OH)3 dissolution. Percolating disturbed soil samples under laboratory conditions with artificial acid soil solutions undersaturated to Al(OH)3 solids resulted in high rates of Al release in the 30–40 cm layer and revealed Al(OH)3 as a possible Al‐activity controlling solid. The laboratory findings are not in coincidence with field observations. This discrepancy with respect to the regulation of Al activity in the 30–40 cm layer is attributed to the effect of soil structure and the interaction of macropores and micropores under field conditions. Al activity of the soil solution in the 0–10 cm layer seems to be regulated by exchange reactions with organic substances.