DEPOSITION OF ATMOSPHERIC CONSTITUENTS AND ITS IMPACT ON NUTRIENT BUDGETS OF OAK FORESTS (QUERCUS-PETRAEA AND QUERCUS-ROBUR) IN LOWER AUSTRIA

Geochemical processes in central European oak ecosystems (Qercus petra ea and Quercus robur) suffering stand decline were studied in two oak stands of the Weinviertel, Lower Austria, about 30 km north of Vienna. Stores of chemical elements were determined by soil and biomass inven tories. Deposition input was monitored over a 2 year period by bulk sa mpling of throughfall. Soil solution chemistry was studied by tension lysimetry over a 1 year period. Mineral nutrition of oak was judged by foliar analysis. Bulk deposition rates were 10-12 kg N ha(-1) year(-1 ) and 15-20 kg S ha(-1) year(-1). Total annual nitrogen gain is high. Both systems lose calcium and magnesium. Foliar nutrient levels indica te sufficient nutrition with main mineral nutrients, except for magnes ium, which is in moderately low supply. Based on these findings, the h ypothesis that pollutant deposition has been the cause of a sudden and severe appearance of decline symptoms in the second half of the 1980s must be dismissed. The data on deposition rates and ecosystem nutrien t status, however, indicate that the soil of both systems is acidifyin g, nitrogen stores are increasing, and magnesium pools are depleted. I f deposition of pollutants continues at current rates, a slow but stea dy degradation of many oak ecosystems in the Austrian Weinviertel is i nevitable.