Ozone-induced symptoms on native forest vegetation in Switzerland with confirmation via controlled exposures
Rationale
Ozone is one of a number of air pollutants involved in long-range transport. Several recent reports have documented ozone-induced foliar injuries to forest vegetation and crops in America and some Mediterranean countries, but such records are relatively rare in central Europe. Long-range transport of tropospheric ozone and its pollutant precursors has been identified in southern Switzerland, with northern Italy being the most likely source region and the mid-elevation forests of Canton Ticino being the most highly exposed under normal summer wind trajectory patterns. Indeed, recent surveys of sensitive species such as Prunus serotina and Robinia pseudoacacia (photos), together with preliminary experimental studies have indicated the presence of ozone-induced foliar injuries in Canton Ticino.
Project aims
The aims of this project are:
- to assess the extent of ozone-induced foliar injuries to species of plants native to the forests of southern Switzerland (TI and VS), and
- to confirm the cause of injury by controlled exposures in continuously stirred tank reactor chambers (CSTRs) in conjunction with open-top chambers (OTCs).
The value of these species as bioindicators in the LTFER and Sanasilva plots will then be determined. The location of the project is aimed at identifying the extent of injury caused by transboundary (Italy-Switzerland) ozone.
The work will also contribute to the difficult issue of setting ozone standards for forests and other types of natural vegetation.
Methods
Potential ozone-induced injury on native plants is being assessed by field evaluation. Seed or suitable propagation stock is being collected from symptomatic and asymptomatic individuals of species showing symptoms. This material has been or will be planted in CSTRs at PennState University and exposed to ambient and near-ambient concentrations (typical of cantons Ticino and Valais) of ozone. The symptom responses observed under the known ozone-exposure conditions are being compared with field observations. Further confirmation of the causes of the observed symptoms is being obtained under ambient ozone - filtered air conditions using the open-top chamber facility established at Morbio Superiore in Ticino.
Work plan
A variety of species are being tested in the CSTR facility at Pennsylvania State University. These will be supplemented by further collections during 1997.
In the first year of the project, the following species have been planted in the chambers at Morbio Superiore: Acer pseudoplatanus, Betula pendula, Cornus sanguinea, Corylus avellana, Fagus sylvatica, Fraxinus excelsior, Morus nigra, Prunus avium, Prunus serotina, Rhamnus cathartica, Rumex acetosa, Sambucus racemosa, and Viburnum lantana (Photos). The plants will be remain in chambers for two years. These are all species on which foliar symptoms similar to those caused by ozone have been identified in Ticino.
Visible injury is assessed using the Horsfall-Barratt rating system. This is based on the extent of injury on a leaf and the number of leaves affected.
Participants
- Peter Bleuler
- Christian Hug
- John Innes
- Werner Landolt
- Christoph Scheidegger
- John Skelly (PennState University, Department of Plant Pathology)
- Ken Snyder (PennState University)
- David VanderHeyden (PennState University)
Contact
