Effect of ambient ozone and acid mist on aphid development.

The effect of ambient air with increased ozone concentrations and artificial acid mist on the population growth of two different aphid species was studied: Aphis fabae on Phaseolus vulgaris and Phyllaphis fagi on seedings of Fagus sylvatica. Whereas the ambient air inhibited growth of Aphis fabae, it stimulated population growth of Phyllaphis fagi. In Fagus, analysis of a phloem exudate revealed that the amino acid/sugar ratio was significantly increased by the ambient air compared to filtered air.

Short-term canopy interactions of beech trees: mineral ion leaching and absorption during rainfall.

Mineral nutrient composition of the stemflow of 70-120-year-old beech trees Fagus sylvatica L. in 26 stands in northwestern Switzerland was compared with that of incident precipitation. Four mm of precipitation was sufficient to wash-off the bulk of the dry deposition intercepted by the canopy.

The influence of NaCl on leaf water relations and the proportions of K, Na, Ca, Mg, and Cl in epidermal cells of Fraxinus excelsior L.

The influence of NaCl on leaf water relations was investigated in 3-4-year-old, potted Fraxinus excelsior L. trees. Until midsummer, the application of NaCl to the soil resulted in increased leaf water potentials (Psi) and stomatal diffusive resistances (r(s)).

Factors contributing to forest decline in northwestern Switzerland.

Possible causes of decline of 37 beech (Fagus sylvatica L.) forests in northwestern Switzerland were investigated. The trees were assessed for symptoms of damage or disease including loss of leaves, chlorosis and dead shoots.