NUTRITION RESPONSE OF NORWAY SPRUCE AND WILLOW TO VARYING LEVELS OF CALCIUM AND ALUMINUM

Decreased forest tree growth has often been attributed to increasing soil acidification, especially from high concentrations of soluble Al3+ and low base saturation. The growth of willow cuttings (Salix viminalis L. 78183) and Norway spruce seedlings (Picea abies L. Karst) were measured in a greenhouse in the presence of variable Ca2+ at uniform NH4+ concentrations. Sets of willows were grown in sand culture, one watered with Ingestad's nutrient solution (INS, pH 5.4) and the other watered with acidified Ingestad's nutrient solution (NSA, pH 3.8). Three levels of Ca2+ and Al3+ concentrations (in NSA only) were established for all nutrient solutions. Sets of Norway spruce seedlings were grown in calcareous sand and watered with INS, one of pH 5.4 and the other of pH 2.1 (resulting in two Ca2+ concentrations after acid neutralization by CaCO3). In the field, observations were made on the correlation of naturally occurring soil solution Al3+ and Ca2+ to spruce needle Al, Ca2+ and N concentrations. In the willow studies, both the above- and below-ground biomass were negatively influenced by the presence of Al3+. Aluminium decreased the growth of rooted cuttings (more in roots than shoots), reduced the uptake of N, Ca2+, Mg2+ and P, significantly lowered the weight of fine roots, and caused overall reductions of tissue nutrient concentrations. As Al3+ concentrations increased, increased concentrations of Ca2+ were needed by the willow to help ameliorate the effects of Al3+. In field samples of spruce needles and soil, CAB (CAB = Log10 Ca2+/Al3+) was positively correlated with N concentration. From a combination of greenhouse and field studies the mechanisms for Ca2+ amelioration of Al3+ toxicity in trees appear to be i) the effect of Ca2+ on reduced absorption of Mn2+ and Al3+, ii) the effects of Ca2+ on NH4+ and P absorption, iii) and the stimulation of tree growth.