Soil Acidification and Excess Nitrogen Deposition - a Threat to Austrian Forests? : Proceedings of the Joint Symposium "Environmental Threats to Forest and Other Natural Ecosystems" held at the University of Oulu, Finland, November, 1-4, 1988 : Ecological impact of acidification

1989

10 Abb., 1 Tab., 11 Lit

Unselbständiges Werk

14272

200060801

Measurements of the deposition rates of atmospheric trace constituents to forest ecosystems in Austria have shown that the average proton deposition is less than 0.5 kmol per hectare per year; however there is considerable regional and even local variability. The deposition of plant utilizable nitrogen compounds into the nitrogen cycle of Austrian forest ecosystems ranges from 12 kg N to more than 30 kg N per hectare per year. Locally, even higher deposition rates are encountered as a consequence of point sources or special deposition mechanisms such as fog interception, hoar frost deposition, and accumulation in snow drifts. In order to place these values into perspective, they are compared with the impact of natural processes such as erosion or deposition of litter and with the impact of modern forestry as well as historic land use on acid base realtions and nitrogen dynamics of forest ecosystems. It is evident that acidification from both natural litter erosion and litter raking may exceed acidification due to the present deposition of acidifying compounds. Nitrogen depletion and acculumation by natural processes may also be substantial. Litter deposition on the downward side of crests or in dells has over millenia added large amounts of nitrogen to the nitrogen stores of these micro-sites. however, since plant nutrients in addition to nitrogen were introduced with the deposited litter, such ecosystems differ from ecosystems where nitrogen is introduced from atmospheric deposition without a concurrent deposition of basic cations. Presently soil acidification due to the deposition of acids and ammounium must be considered serious in many areas in Austria. Mineral deficiencies are common in Austrian forests and are in part probably a consequence of excess nitrogen deposition. In the future, soil amendments and fertilizer applications to counteract negative effects of pollutant deposition on tree nutrition and on nitrogen dynamics of forest ecosystems will become a necessity in many Austrian forests.