THE EFFECT OF ACID-RAIN TREATMENTS ON THE SUSCEPTIBILITY OF PINUS-SYLVESTRIS TO GREMMENIELLA-ABIETINA

Scots pine (Pinus sylvestris) seedlings were planted in a nursery bed 20 cm thick. The substrate had been removed from an illuvial horizon i n the soil underlying a stand of Scots pine in Finland, which had suff ered from severe infection by Gremmeniella abietina. The seedlings wer e irrigated for 3 years, applying three pH levels (2.5, 3.5, and 4.5) using sulphuric acid, nitric acid, and a 3:1 mixture of sulphuric and nitric acid. The pH of the pure water used in the control treatment wa s 6.1-6.4. The seedlings were inoculated with the conidiospores of G. abietina to find out their susceptibility to infection with the Sclero derris canker disease. Because to the adequacy of its buffering capaci ty, the soil was observed to become more acidic only in the treatments at pH 2.5. The concentrations of extractable Ca and Mg cations decrea sed while the concentration of Al and Fe increased with soil acidifica tion during the 3-year experiment. Acidification did not increase the susceptibility of Scots pine to infection by the Scleroderris canker. Seedling growth was at its maximum in the acidification treatments whe re most nitrogen was added.