Effect of clear-felling and slash removal on the acidity of Northern coniferous soils

Measurements of pH were carried out at two experimental sites in Sweden before and after clear-felling. At eleven sites, pH, cation-exchange capacity, base saturation and exchangeable hydrogen ions were compared in clear-felled areas where slash was left and removed, respectively. It is shown that pH increases significantly after clear-felling. The increase is larger than can be explained by the release of basic cations in connection with decomposition of slash and humus. The increase in pH is less in a clear-felled area when the slash is removed than when it is left. There is a decrease in exchangeable Ca²⁺, Mg²⁺ and Mn²⁺ and an increase in H⁺ and Al³⁺. There is a decrease in base saturation of about 80%.