For two soils under mature Scots pine (Pinus sylvestris) forest in Southern Germany (Pfaffenwinkel, Pustert), the chemical status of the topsoil (forest floor, mineral soil down to 30 cm) has been investigated in 10-yr intervals over a period of 22 and 30 years, respectively. At each site, 12 soil samples taken from randomly assigned control plots of forest amelioration experiments were analyzed. At Pustert, the C/N ratio in the forest floor decreased from 36.5 in 1974 to 30.0 in 1984, 26.2 in 1994, and 23.0 in 2004; the N pool in the forest floor increased from 0.5 to 1.1 Mg ha-1. A similar trend was observed for Pfaffenwinkel, where the C/N ratio changed from 35.4 in 1982 to 32.9 in 1994, and 29.2 in 2004; the forest floor N pool increased from 1.3 to 1.6 Mg ha-1. The pH (0.01 M CaCl2) in the forest floors of both soils did not change, but remained at a constant value of 2.75 (Pfaffenwinkel) and 3.3 (Pustert). In the mineral topsoil of Pustert, the pH decreased systematically and significantly during the past 30 years, whereas no systematic change was noticed at Pfaffenwinkel. Also the base saturation of the mineral soil, which already was low at the beginning of the monitoring period (Pfaffenwinkel: <5%; Pustert < 15%) decreased systematically during the monitoring period. Between 1982 and 2004, the top 20 cm mineral soil of Pfaffenwinkel lost about 30% of its exchangeable Mg pool and 10% of its exchangeable Ca pool; at Pustert, 30% of the exchangeable pools of K and Mg got lost between 1974 and 2004. The results show a significant and considerable N accumulation, acidification, and base cation depletion for both soils during the recent 30 years, with atmospheric acid and N deposition probably being the main driving process.