Combined effects of acid mist and frost on the water status of young spruce trees (Picea abies)

Acid mist (pH 3) precipitation led to a degradation of the epicuticular waxes of the youngest needles. Under the influence of frost drought in spring those affected trees resulted in a detrimental decline in needle water potential and turgor potential. The results indicate that a damaged, poor cuticle loweres the water retention capability and increases water losses by non stomatal, cuticular transpiration. Therefore acid mist treated trees seem to be more endangered to water stress under frost drought conditions in spring than trees with an intact cuticula. The results are in agreement with observations of decline symptoms under field conditions after years of drought. The influence of mist acidity in combination with frost simulatio during winter time were of minor importance.