How Reproducible are the Reactions of Stress Indicators for Sitka Spruce Treated with Acid Mist?

SHEPPARD L.J. 1996. How reproducible are the reactions of stress indicators for Sitka spruce treated with acid mist? Phyton (Horn, Austria) 36 (3): (23) (30). Results of previously published experiments based on open-top chambers and field exposure systems with seedlings, mature grafts and physiologically mature trees (<13m tall) of Sitka spruce exposed to pH 2.5 mist are discussed briefly for the purpose of identifying reproducible bioindicators of acid mist induced perturbation, i.e. physiological disturbance causing stress (reduction in performance). None of the bioindicators studied, i.e. visible injury, foliar nutrient concentrations, ion leakage with and without freezing, and growth responded consistently to treatment. Substantial treatment by environment interactions were detected in treatment effects on visible injury and foliar nutrient concentrations. But the enhancement of ion leakage from unfrozen shoots and changes in foliar nutrient concentrations in treated compared with untreated shoots reliably indicated acid mist-induced stress.