EFFECTS OF ATMOSPHERIC AMMONIA ON VEGETATION - A REVIEW

Atmospheric ammonia does not only cause acute injuries at vegetation c lose to the source, but significantly contributes to large scale nitro gen eutrophication and acidification of ecosystems because the amount of sources is high and after conversion to ammonium it can reach remot e areas by long-range atmospheric transport. Besides having acute toxi c potential, NH3 and NH4+ (= NH(y)) may disturb vegetation by secondar y metabolic changes due to increased NH(y) uptake and assimilation lea ding to higher susceptibility to abiotic (drought, frost) and biotic ( pests) stress. Prevention of damage to natural and semi-natural ecosys tems will only be achieved if NH3 emissions are drastically reduced. I n this paper, the current knowledge on NH(y). emission, deposition, an d its effects on vegetation and ecosystems are reviewed. Critical leve ls and critical loads for nitrogen deposition are discussed.