Connections Between Climatic Conditions and the Nutritional Status of Spruce Needles Determined from the Austrian Bio-Indicator Grid

Data material from the Austrian Bio-Indicator Grid was used to examine potential connections between extreme climate conditions and certain needle parameters. From 1983 to 1995 1,120 spruce trees were sampled annually in October. Samples were examined for needle mass (weight of 100 needles in mg) and macronutrient concentrations (% N, % P, % K, % Ca, `% MG). Based on the analytical results, the annual mean values of the needle masses, the nutrient element masses (mg of element per 100 needles) and the nutrient ratios (N/P, N/K, N/Ca, N/Mg, K/Ca, K/Mg, Ca/Mg) were calculated. Extreme weather events were assessed using the deviations of the monthly means of the vegetation period (April to September) from the respective longterm mean (30-year period). Needle parameters were most significantly influenced by the extremely hot and dry summer of 1992. Monitoring results from that year showed the lowest annual mean for needle mass and the lowest nutrient masses for N, P, K and Mg. It was proved that hot and dry weather had influenced also the needle data of other years, though less markedly than in 1992. Results clearly showed that climatic conditions must be considered in the interpretation of needle data. This requires the comparison with data from long-term monitoring.

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