Changes in the soil sorption complex of forest soils in Poland over the past 27 years.

Soil acidification due to natural factors and acid deposition is expressed in changes in soil properties such as pH, cation exchange capacity (CEC) and Al saturation. The aim of this work was to establish whether the soil sorption complex of forest soils in Poland was subject to changes over the period 1978-2005. The removal of base cations from the soil sorption complex was observed. The intensity of cation leaching depends, inter alia, on the soil type and vegetation cover. Changes occurring over the past 27 years are best recognized in the saturation of CEC with base and acid cations. The composition of CEC, expressed as series of decreasing proportions of cations, showed replacement of Ca with H ions in the Rustic Podzol; a shift of Ca and Mg towards lower percentages and an increase in the proportion of H in the Eutric Cambisol and a drastic decrease in the Mg contribution in the Haplic Podzol. This suggests that the ion composition of CEC may be used as an efficient index for evaluating the acidification process.