title: The effects of ozone and acid mist on Scots pine saplings.
abstract: It has been suggested that the forest decline ("Neuartige Waldschäden") seen recently in parts of West Germany is due to the direct effects of ozone combined with acid mists, rather than soil-mediated effects of acid deposition. It has been proposed that ozone (a) makes the needles of affected conifers more susceptible to leaching by acid mist and (b) damages the photosynthetic apparatus, giving rise to diminished carbohydrate reserves which reduce the ability of affected trees to replace the leached nutrients. This nutrient deficiency (especially of Ca and Mg) is a characteristic symptom of the Waldschäden, which progresses through growth decline, needle loss, and eventually death. Parts of this hypothesis were tested in a preliminary experiment in which 3-year old Pinus sylvestris (Scots pine) saplings were exposed to 4 different O3levels, with and without acid mist (pH 3) treatment, for 56 days between July and September, 1983 in outdoor 'solardome' fumigation chambers. The visual symptoms observed at >100 μg m-3were more characteristic of the chlorotic mottle seen on O3-affected trees in the USA than the general chlorosis of affected stands in Germany. O3at mean concentrations of >200 μg m-3for 56 days reduced the fine root biomass and accelerated the senescence of older needles, in keeping with field effects observed in Germany. However, these O3levels increased, rather than decreased, the concentrations of most elements in the needles. Acid mist had no effect on needle concentrations, and there was no O3-acid mist interaction. O3up to 300 μg m-3also had no effect on the amount of ions leached from the needles, whereas acid mist increased the leaching of some ions, and again there was no interaction. The only nutritional effect of O3was to reduce the foliar uptake of NO-3from the acid mist solution. An aphid infection part way through the experiment caused a large increase in leaching, particularly of K, and affected the intermediate O3and watersprayed plants most. Caution is needed in extrapolating these results to the field, as the experiments were of short duration on young trees with fully-formed needles, growing in a soil better supplied with nutrients than field soils. Nevertheless, these preliminary results do not support the hypothesis of an O3-mediated increase in foliar leaching as the major cause of forest decline nor were the symptoms of O3-injury on Scots pine comparable with those reported in the field.
authors.affiliation: Central Electricity Research Laboratories, CEGB, Kelvin Avenue, KT22 7SE, Leatherhead, Surrey, U.K.
authors.forename: R A
authors.initials: RA
authors.lastname: Skeffington
authors.affiliation: Central Electricity Research Laboratories, CEGB, Kelvin Avenue, KT22 7SE, Leatherhead, Surrey, U.K.
authors.forename: T M
authors.initials: TM
authors.lastname: Roberts