Acidification of soils in five catchments in Norway

Soil plots were established in catchments within the frame of the Norwegian Monitoring Programme for Long-Range Transported Air Pollutants. Four soil plots of about 10 m by 20 m were established within each catchment in areas with relatively homogeneous soil and vegetation. Multiple soil cores were taken at 50 points in a grid from each plot (repeated 4 times) and the samples were pooled by depths. Each soil core was divided by soil horizon, by predefined depths or by a combination of these, usually giving one soil sample for each 2-cm-depth down to about 15 cm. The soil pH measured in water suspension varied for all soils between 3.5 and 4.9. Base saturation measured at pH 7 varied between 2% and 22% with the highest values in the upper, more humus rich layers. All of the monitored catchments include acid soils poor in base cations. After 8 years the plots were resampled using the same procedure as for the first sampling. In most of the plots a decreasing pH trend from the first to the second sampling was measured. However, the base saturation was generally higher in all plots at the second sampling compared with the first. There are no clear effects of the different pollution regimes in the various catchments. It must be emphasized, however, that 8 years is a short period for measuring long-term soil changes.