Foliar mineral composition, fertilization and dieback of Norway spruce in the Belgian Ardennes

Needles from healthy Norway spruce (Picea abies (L.) Karst.) at Willerzie in the West Ardennes and from trees with symptoms of dieback at Langesthal in the East Ardennes were analyzed by age class for mineral composition. Both stands were on acid oligotrophic soils. At Willerzie, needles were sampled from plots fertilized 12 to 17 years earlier (dolomitic lime plus N, P and K) as well as unfertilized plots. Effects of fertilization included increased levels of calcium, manganese, phosphorus, and copper and reduced levels of total sulfur, sulfate-S, sulfate-S:total S, potassium and aluminum. Levels of calcium, magnesium, copper and boron were low at both sites and, at Langesthal, calcium and magnesium may have been deficient. Sulfur level was normal at Willerzie, but at Langesthal, mean sulfur content for needles of all age classes was 198 mg 100 g(-1) dry weight, a level that may be toxic. In older needles, the N:S ratio at Langesthal was below the threshold value of eight reported to be necessary for healthy growth. Other symptoms of stress observed were high sulfate-S:total S and nitrate-N:total N ratios. At Langesthal, manganese level was probably adequate although only one-fifth the level at Willerzie. Levels of aluminum and iron were very high at both sites. Most of the iron and much of the aluminum occurred as a surface deposit that could be removed by washing the needles in chloroform.