THE EFFECTS OF SIMULATED ACID RAIN ON GERMINATIVE CAPACITY, GROWTH AND MORPHOLOGY OF FOREST TREE SEEDLINGS

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Abstract
Summary: Acid rain‐induced direct injury to forest tree seedlings was investigated in specially designed controlled‐environment simulated‐rainfall chambers. Seed germinative capacity, seedling survival, seedling growth and morphological responses to simulated rains of pH 5.6, 4.6, 3.6 and 2.6 were examined during the first growth cycle in 11 commercially important north temperate tree species. Germinative capacity was weakly responsive to rain pH, while seedling survival was more sensitive. No evidence of macroscopic foliar injury was observed at rain pH > 2.6. 1 reatment with pH 4.6 rain was sufficient to induce statistically significant growth reductions and morphological changes in coniferous seedlings. Response varied with species, treatment pH and parameter measured. No consistent growth stimulations were observed. Initiation of Primary needles, axillary meristems and shoot apex height were most affected by simulated pH. Deciduous species were considerably more resistant than coniferous species. Treatment with ram of pH 2.6 was generally required to induce significant growth reductions in deciduous seedlings.