Influence of Various Stresses on Ca and Mg Nutrition of a Spruce Stand Developed on Acidic Soil.

In order to understand the relative influence of sylviculture and atmospheric deposition on spruce yellowing, an input/output budget has been developed in 3 adjacent stands of increasing ages. It appears that both forest growth and atmospheric deposition influence soil desaturation, growth being the major factor of soil impoverishment in young stands, and pollution acting mainly in old ones. An experimental drought has proved able to amplify spruce yellowing. However, this factor is unlikely to be directly responsible for the broadly extended Mg deficiencies. Spruce seedlings grown on one of these soils show yellowing symptoms although they grow healthily, when the soil is previously pasteurized. A deleterious microflora might be the link explaining the development of spruce yellowing in the Vosges.