Amelioration of Magnesium Deficiency in a Norway Spruce Stand (Picea abies) with Calcined Magnesite

Norway spruce has shown needle yellowing and defoliation symptoms on manysites of the Bohemian Forest in north central Austria since theearly 1980s. A forest amelioration experiment was set up toevaluate the response of spruce to magnesite based fertilizerswith different solubilities. Response variables were a crownvigor index, diameter growth, nutrient contents in needles,soil solution chemistry, and soil chemistry. Soil solution atfertilized plots showed an immediate response in base cationconcentrations, nitrate concentrations and pH-values.Fertilization increased the pool of exchangeable cations in theupper 15 cm of the soil and reduced levels of exchangeable Al. Themagnesium and calcium content of the needles of dominant trees wasgreatly improved. Fertilization has increased the mineralizationrate of soil organic matter. Diameter growth, as a measure of treevigor, showed a pronounced positive response with a time delay of5 years. Our results demonstratethat magnesite based fertilizers are a viable option to improvethe nutritional status of spruce forests on granitic bedrock.