Acidity Properties in Swedish Forest Soils-Regional Patterns and Implications for Forest Liming

The chemical status within a subset of Swedish forest soils representing Spodosols and acid Entisols and Inceptisols at mesic sites is reported. Three regions which differ in climate and deposition, southwestern (SW), southeastern (SE) and northern (N) Sweden are compared. Most of the soils are located on acid siliceous bedrock. The three regions differ in the percentage of sample plots where the value of a given variable exceeds the mean calculated for the whole country. The order of decreasing frequency in the 0 and B horizons is N>SE>SW for base saturation, calcium saturation and magnesium saturation, and N>SW>SE for potassium saturation. For aluminium saturation the order is SW=SE>N in the 0 horizon and SE>SW>N in the B horizon. The regional difference is especially pronounced with respect to the calcium saturation in the B horizon. The percentage figure is 13, 37 and 45 in SW, SE and N respectively. 33 and 38% of the sample-plots in SE and N respectively have a calcium saturation <1% of CEC, the corresponding figure for SW being 73 %. Different liming criteria and the possible need for forest liming are discussed.