Chemical composition of the humus layer, mineral soil and soil solution of 200 forest stands in the Netherlands in 1995

Abstract

A nationwide assessment of the chemical composition of the soil solid phase and the soil solution in the humus layer and two mineral layers (0-10 cm and 10-30 cm) was made for 200 forest stands in the year 1995. The stands were part of the national forest inventory on vitality, included seven tree species and were all located on non-calcareous sandy soils. The soils are nearly all characterized by high nitrogen and metal contents in the humus layer ans low pH and base saturation values in the minerallayer, indicating the occurrence of eutrophication, acidification and heavy metal pollution. Of those stands, 124 were also sampled and analysed in 1990. Compared with 1990, results for the humus layer show a decrease (release) in nitrogen and metal contents and pools, and a decrease in total and exchangeable pools of base cations, combined with increase in hydrogen saturation. This indicates a decrease in eutrophication but an ongoing acidification. The soil solution, however, shows a decrease in Al/Caand NH4/K ratios, implying a slight recovery from acidification. For the mineral soil, the changes in element pools are too unreliable to draw any distinct conclusion