REVITALIZATION EXPERIMENTS IN MAGNESIUM DEFICIENT NORWAY SPRUCE STANDS IN AUSTRIA

Amelioration of degraded forest ecosystems on acidic substrates showin g the new type of forest decline is a major goal of forest management. A number of experiments show positive effects of Mg-application to sy stems suffering from Mg-deficiencies. The current paper compares exper iments conducted in the Austrian part of the Bohemian Massif, where bo th effects on soil solution chemistry and effects on plant nutrition, vitality and growth were investigated. It turned out that any type of Mg-source is able to improve Mg-nutrition of trees; both a neutral sal t like KIESERITE as well as alkaline reacting magnesite and dolomite d erived materials. A positive reaction of vitality and growth could how ever only be induced with dolomitic lime or magnesite. Using mineral N PK fertilizers, even with high Mg-content, induced Mg-deficiencies and led to nutritional imbalances. In addition significant NO, leaching o ccured. On the other hand an organic slow release fertilizer (BACTOSOL ) amended with magnesite derived fertilizers (BIOMAGc*) led to balanc ed nutrition and a fast recovery of tree health status, as judged by c rown transparency, vitality index and growth rates. In both cases, whe n either magnesite derived compounds or combinations with the organic slow release fertilizer were applied, NO3- leaching occured only durin g the first three years after fertilization. The leaching rates declin ed afterwards to values comparable to unfertilized plots, while Mg-con tent of the soil solution could be elevated compared to the CONTROL, s howing the sustainability of proper fertilization.