NUTRITIONAL AND MICROBIOLOGICAL ASPECTS OF DECLINE IN THE VOSGES FOREST AREA (FRANCE)

The aim of this study was to experimentally determine a possible influence of microbial or chemical properties of soil in Norway-spruce decline. Soils collected from declining and healthy forest sites of the Vosges were subjected to a range of soil treatments. Three glasshouse experiments were conducted. Soil is directly involved in the spruce decline by inducing nutrient deficiency, which can be partially corrected by fertilization. The addition of calcium carbonate increases mycorrhizal status and restores normal mineral nutrition (especially phosphorus nutrition) and growth. The low pH of the soils and the presence of a noxious microbial factor are involved in the poor mycorrhizal infection and nutrients status of Norway spruce. Fungi rather than other microorganisms could be involved; they cause no root necrosis, and might be some species of Penicillium, Trichoderma, Acremonium or Cylindrocarpon regularly recovered from the roots. This microbial component involved in the reduced mycorrhizal development of seedlings could be suppressed by soil pasteurization and fungicide application. Possible remedial treatment of declining spruce stands in the Vosges should include liming and fertilization. © 1990.