HOW REPRODUCIBLE ARE THE REACTIONS OF STRESS INDICATORS FOR SITKA SPRUCE TREATED WITH ACID MIST

Results of previously published experiments based on open-top chambers and field exposure systems with seedlings, mature grafts and physiolo gically mature trees (<13m tall) of Sitka spruce exposed to pH 2.5 mis t are discussed briefly for the purpose of identifying reproducible bi oindicators of acid mist induced perturbation, i.e. physiological dist urbance causing stress (reduction in performance). None of the bioindi cators studied, i.e. visible injury, foliar nutrient concentrations, i on leakage with and without freezing, and growth responded consistentl y to treatment. Substantial treatment by environment interactions were detected in treatment effects on visible injury and foliar nutrient c oncentrations. But the enhancement of ion leakage from unfrozen shoots and changes in foliar nutrient concentrations in treated compared wit h untreated shoots reliably indicated acid mist-induced stress.