Changes in soil acidity in two forest areas with different acid deposition: 1920s to 1980s

The aim of the present paper is to compare changes that occurred from the period 1926-27 until the period 1982-85 in stands of different ages in two areas with different acid deposition load and different forest history. The relative roles of tree species stand age, and acid deposition for soil acidification are discussed. Soil horizons in two forest areas with different climate, history and acid deposition load were examined electrometrically for acidity in 1926-27 (pH/sub aq/) and re-examined in 1982-85. The deeper soil horizons beneath coniferous stands were more acid in southwestern Sweden than those in northern Sweden already 1926-27. The new pH measurements indicate that the recent rate of acidification is higher in the southwestern than in the northern sites. There is no evidence that existing differences in forest history, climate, or soil mineralogy would explain this difference. The most likely explanation is the difference in acid deposition load. (authors).