Tree Bark - Sensitive Biotest for Environment Acidification

The Niepolomice Forest, a large forest complex (11,000 ha), situated about 20 km from a large steel Mill and about 40 km from the city of Cracow was the object of study. Sulphur dioxide emitted by the steel mill and the city has already caused acidification of the environment of the Niepolomice Forest. The degree of such acidification was estimated using tree bark as a bioindicator. The pH value and buffer capacity were determined for three tree species - Quercus robur, Tilia cordata and Pinus sylvestris. The bark of all trees showed acidic reaction ranging from pH 2.2 to 4.7. Difference in pH of bark were found between various localities. The bark of examined species was much more acidic in the western part in the Niepolomice Forest than in the eastern part of the forest complex. The buffer capacity of bark also differs in various localities increasing with SO2 concentration in the air. A good correlation between acidification of tree bark and the concentration of SO2 in the air of Niepolomice Forest was found; therefore tree bark may be regarded as a good bioindicator and recommended for practical use to estimate the degree of air pollution. The procedure of sampling and analysis of tree bark is described in detail.