The effect of liming on quantity and chemical composition of soil organic matter in a pine forest in Berlin,Germany

The study was carried out in a 40-yr old pine plantation on a Cambic Arenosol within the urban area of Berlin. Lime application (6.1 t ha^-1) has led to a pH increase in the forest floor from 3.3 to 5.5 within one year and to a strong stimulation of macrofaunal and microbiological activity. Three years after liming, the C:N ratio of the forest floor decreased from 28 to 25 and P, Pb, Zn, Cu and Cd concentrations in organic matter increased significantly. The organic C pool of the forest floor was almost 7 t ha^-1 lower in the limed plot which is attributed to increased microbial respiration. In the mineral soil too, C-pools are lower in the limed plot, amounting to 13.2 t ha^-1 or 14% less than in the control. C:N ratios have narrowed significantly from 27–29 to 23 in 10–30 cm depth. The humic acid fraction is lower throughout the limed profile while the percentage of fulvic acids has increased significantly below 10 cm. The results point to severe losses of organic matter and to profound changes in its composition. This may be of consequences for site quality and leaching processes.