Impact of dolomite lime on vegetation and fungi in the oak and the Norway spruce stands of Belgian Ardenne (Hestreu) | Reponse d'une chenaie et d'une pessiere ardennaises (Hestreu) a un amendement calcaro-magnesien : impact sur la phytocenose et la mycocenose

In the Walloon region, soil acidification, and consequent calcium and magnesium deficiencies, are pointed out as major causes of forest decline observed for about twenty years. Liming is then proposed to counteract these effects and to enhance health of hardwoods and conifers forests. The reaction of vegetation and fungi to dolomite lime supply at a rate of 5 t ha exponent-1 (1,5 t ha exponent-1 CaO, 800 kg ha exponent-1 MgO) has been survied during 4 years after treatment in a oak and a Norway spruce forests. The crown health of limed oaks became stable, and needles yellowing of spruce, due to magnesium deficiencies, has disappeared 3 years after dolomite application. Foliar analyses gave evidence of a better calcium and magnesium nutrition for both tree species. Tree rings analyses didn't reveal any change in radial increments after liming. The herb-layer floristic richness increased from the first year following liming, with the appearance of ruderal and N-demanding species, especially under spruce cover, where initial vegetation was scarce and competition was very low. The initial vegetation didn't react significantly to treatment. The moss layer was hardly affected, showing a decrease in frequency and cover of acidophilous dominant Dicranaceae species. Some neutrophilous competitive or stress tolerant species were spreading out and some ruderals appeared. The fungi showed great annual variations in sporocarps formation. Some species, especially litter decomposers appeared in great numbers after liming. The study of ectomycorrhizal symbiots at the root level of oaks and spruces lead to the recognition and description of the more abundant morphotypes connected with the two tree species. The global mycorrhizal rate was low, especially in spruce. The sporocarps and root levels of analyses partially agreed.