Box 34A Forest damage in the Krusné Hory, Czech Republic
Dying forest
The forest decline in northern and western former Czechoslovakia is unmistakable. This region emits a significant fraction of Europe's sulphur dioxide, nitrogen oxides and toxic metals as the result of an economy based heavily on mining and burning of lignite and coal, heavy industry and building material production (cement manufacturing). From the early 1960s, foresters first noted the decline and then the collapse of forests in the mountainous Erzgebirge region. Some 100 000 hectares of Norway spruce (Picea abies) forests have died, and it is estimated that a total of 54 per cent of the forests in the Czech Republic have suffered irreversible damage (Moldan and Schnoor, 1992). Dry deposition of sulphur dioxide and sulphate is aided by efficient collection in forest canopies. The problem is severe. Annual average sulphur dioxide gas concentrations in the Erzgebirge (100 µg/m3) are about ten times greater than those measured in the Bavarian and Black forests of Germany. Stands that have died are rapidly harvested, and much of the area has been replaced by grassy meadow. Norway spruce in the Erzgebirge is progressively replaced by more tolerant species of spruce (Picea 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.