Long-term patterns in soil acidification due to pollution in forests of the Eastern Sudetes Mountains

Soil acidification was assessed in the Eastern Sudetes Mountains (Czech Republic) between 1941 and 2003, i.e. before and after the period of major industrial pollution (1950s-1990s). The twenty sites included in our study were distributed along a gradient of altitude ranging 1000 m. Values of pH have decreased in 80-90% of the pairs of samples after the six decades, on average by 0.7 for pH-H2O and 0.6 for pH-KCl. Organic matter increased in the topsoil, probably reflecting a change in decomposition conditions. The most important finding is that the acidification varies along the joint gradient of altitude/tree layer composition, and displays a changing pattern in three soil horizons (A, B and C). Contrary to expectations, most acidified were soils in beech forests at lower elevations. - Highlights: → Soil acidification varies along the joint gradient of altitude/tree composition. → Soil acidification displays a changing pattern in topsoil and subsoil horizons. → Acidification rate is stronger in soils of beech forests at lower elevation. → Historical measurements provide a reliable evidence of long-term soil acidification. - Strong acidification decreasing with altitude was observed in forest soils resurveyed after more than half a century.