Vascular tissue anatomy of Norway spruce needles and twigs in relation to magnesium deficiency.

Vascular tissues of needles and twigs of Norway spruce with low foliar magnesium concentrations were examined by light microscopy. Observations were made on samples from (1) apparently healthy trees, (2) trees exhibiting progressive symptoms of decline, including the yellowing and fall of needles and the death of twigs and branches in the subapical canopy, and (3) trees recovering from symptoms of decline after fertilization with magnesium sulfate. Abnormalities in cambium and phloem anatomy, which were apparent in 2-year-old needles of declining trees, were seen only in needles at least 4 years old in healthy trees, suggesting that needles of declining trees are susceptible to precocious aging. Abnormalities in xylem anatomy were observed in needles 3 years or more in age in declining trees, but were never seen in needles of healthy trees. Over time, anatomical abnormalities in declining trees were seen in progressively younger twigs, which may explain the acropetal development of decline symptoms. After fertilization with magnesium sulfate, normal phloem and xylem were observed in the newly formed tissues.

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.