pungens).
The longest legacy of the past 40 years may be the build-up of toxic constituents in the region's soils. Foresters have scraped away the top 15 cm of soil with bulldozers into wind rows in order to get seedlings to survive. They feed the soil with limestone and fertilisers, but regeneration remains poor. Metals (aluminium, arsenic, beryllium, cadmium, lead and zinc) make the soil toxic. Small-catchment research has demonstrated that the chemical weathering of calcium and magnesium cannot keep pace with the acidic deposition (Paces, 1985). Aluminium that is liberated from the soil as the pH decreases is toxic to spruce trees. Changes in soil pH were recorded in more than 200 sites in the Czech Republic. A significant decrease in pH was found, from 3.8 in 1960 to 3.3 in 1985. This survey represents one of the few examples in the literature of relatively large-scale soil acidification caused by atmospheric deposition.