Interaction of atmospheric ammonia pollution with frost tolerance of plants : a study on winter wheat and Scots pine

Ammonia (NH3) is one of the major air pollutants in The Netherlands. It originates for almost 90% frorn the intensive livestock agriculture, through the production and spreading of anirnal manure. In areas, where this livestock breeding is concentrated, the mean annual NH3 concentrations are 10 to 15 times higher than natural, background concentrations. From a large number of studies, carried out in connection with the Dutch Priority Programme on Acidification, it was shown that air pollution with ammonia seriously affects plant and ecosystem functioning; it is the main reason for the observed forest decline in The Netherlands.