Współczesne zmiany w ekosystemach leśnych sąsiadujących z obszarami ekologicznego zagrożenia na przykładzie Gór Izerskich

The Sudety, likewise many other mountain areas in Europe, are interesting owing to the visible degradation of the forest ecosystem. One of the reasons causing the degradation is the pollution of the air by solid, liquid and gaseous substances (in consequence, it results in acid presipitations). Location of the big sources emitting pollution near the south-western region of Poland and predominance of the circulation of air from the West in general, cause the situation that the Sudety remain in the zone, that is directly affected by the mentioned sources. During the decade 1984-1994, the observations of the changes in the stand of spruce trees in the lower layer, taking as an example the Izerskie Mountains, were carried on. Observed changes mainly concerned the condition of the sound forest. The condition is defined by the ratio of the number of damaged trees to the whole population (in per cent). The measure of the damage is the loss of the assimilative system and additionally the degree of its overcolouring. Variability of damage process of the stand according to the altitude has been observed. During the decade, in the areas previously deforested, afforestation and restoration took place. The character of vegetation let to ascertain that it was mainly the pioneer forest of the self-sown plants. The favourable trends connected with shrinking of deforested areas could be related to the significant diminishing of the pollution emitted from the areas close to the Izerskie Mountains.