Fertilization of declining conifer stands in the Vosges and in the French Ardennes |
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| Authors: | Maurice Bonneau Guy Landmann Claude Nys |
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| Institution: | 1. I.N.R.A., Center de Recherches Forestières, 54280, Champenoux, France
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| Abstract: | Twenty fertilization experiments were set up in 1985 and 1986 in the Vosges mountains, using mostly calcareous or Mg fertilizers,
in order to verify whether fertilization can attenuate defoliation and yellowing recently recorded in Silver fir and Norway
spruce. In the Ardennes, a fertilization experiment set up in Norway spruce stands prior to the appearance of yellowing was
assessed. In these areas, the total acid deposition is about 2 kg eq H+ ha−1 yr−1. Nitrogen deposition is much more important in the Ardennes (52 kg N ha−1 yr−1 in form of wet and dry deposition) than in the Vosges (16 kg N ha−1 yr−1). The results in the eight adult stands showed no uniform reaction to the treatments. Spontaneous improvement, further deterioration
independently of the treatment, as well as a positive reaction to fertilization were observed. Additional N or P fertilization
sometimes had a beneficial effect on Ca or Mg treatments. The selection of the stands with the best response turns out to
be difficult, as the nutrient contents of needles alone seem not to be a satisfactory criterion for selection. Young plantations
reacted positivley to the treatments. Soluble Mg fertilizer leads to an immediate response. Low solubility Ca-Mg fertilizers
(Ca-Mg lime) did not produce reactions until three years after the application. In the Ardennes, in a 40 yr old spruce stand
suffering from severe Mg deficiency, a Ca and Ca-phosphate fertilization applied 5 yr before yellowing appeared had positive
effects on crown density, discoloration and wood production. Conversely, a single N fertilization in this experiment, as well
as in a young plantation in the Vosges, had a marked negative effect on Mg nutrition, even at low levels. |
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