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ICP Vegetation


International Cooperative Programme on
Effects of Air Pollution on Natural Vegetation and Crops

Chair: Mr. H. Harmens

Head of Programme Centre: Ms. G. Mills

The potential for damage to crops by air pollution in many areas of Europe is high and the annual economic cost may be considerable. The programme was therefore established to consider the underlying science for quantifying crop damage.

The objectives of ICP Vegetation are to:

    (a) evaluate the effects of air pollutants and other stresses on crops and non-wood plants by monitoring the onset of injury and reductions in the yield/biomass of sensitive species;

    (b) identify realistic dose-response functions, incorporating modifying (level II) factors for a range of economically important crops and for crops at risk from pollution;

    (c) validate and substantiate critical levels of ozone for crops and non-wood plants including incorporation of level II factors;

    (d) facilitate the production of European maps showing where critical levels for ozone are exceeded;

    (e) assist in assessing the economic loss due to ozone pollution;

    (f) conduct literature reviews and specific experiments on the accumulation of atmospheric deposition of heavy metals.

The ICP Vegetation is planned and coordinated by a Task Force led by the United Kingdom and supported by a coordination centre at the Centre for Ecology and Hydrology (CEH) in Bangor, United Kingdom. Currently 20 Parties to the Convention actively participate the programme. Attention is focused on ozone-induced damage to crops, as experiments have clearly indicated that crops are sensitive to ozone pollution. Less attention is paid to sulphur- and nitrogen-based pollutants, as these elements are components of fertilizers commonly used in agricultural systems. Ozone effects are also considered for natural and semi-natural vegetation such as grassland and wetland communities. By concentrating on ozone, an extensive database is being compiled for use in the development of protocols for the control of both ozone and nitrogen oxides. The accumulation of atmospheric deposition of heavy metals by plants has recently been included in ICP Vegetation work.

In the experimental programme participants conduct a series of experiments with ozone-sensitive species (e.g. clover) using experimental protocols and equipment supplied by the Programme Coordination Centre. At the end of the experimental season, participants supply data on injury, biomass, phenological development and biomass or yield, together with information on climate, pollution levels, and other abiotic factors. In some countries, supportive research is also conducted to complement the findings of the programme.

Experiments have evaluated the effects of ozone on a range of crops and natural/semi-natural vegetation species. Data on clover have been analysed to establish two short-term critical levels of ozone for visible injury. These consider climatic conditions as well as ozone dose in the five days preceding injury. ICP Vegetation participants have recorded ozone injury on the leaves of over 20 crop species (e.g. maize, potato, soybean, wheat) grown in commercial fields. In 1995 and 1996 experiments were conducted to identify other plants at risk from ozone pollution, and injury was observed on common mallow, creeping thistle, and broad-leaved dock.

The effects of ozone on biomass have been determined at most ICP Vegetation sites by comparing the biomass of ozone-sensitive and ozone-resistant clones of white clover. An earlier method compared the biomass of plants treated with a chemical protectant for ozone, ethylene di-urea, with that of untreated plants. The database generated by these experiments has been used to validate the long-term critical level for yield reduction and to identify important influences on the dose response to ozone.

Further information is available from the Programme Centre.