THE EFFECTS OF LIMESTONE AND OF LIMESTONE PLUS NPK FERTILIZATION ON THE SOIL AND MASS-BALANCE OF A SPRUCE STAND (PICEA-ABIES (L) KARST) IN THE VOSGES MOUNTAINS

Calcareous amendment and/or fertilization trials were carried out in a declining 66-year-old Norway spruce (Picea abies (L.) Karst.) stand in the Vosges mountains (northeast France, altitude 1100 m) in 1985. The aim was to test tree response to nutritional deficiencies (Ca + Mg) and to alleviate soil acidity. In 1988, experimental equipment was set up to collect atmospheric input (bulk precipitation, throughfall) and soil seepage water. The soils are podzolic ('ocre-podzolique'), derived from an acid-poor granitic bedrock ('granite du Valtin'). The soils are coarsely textured, hence very porous. They are very acid (pH 3.4 in the A1 horizon, and pH 4.1 in the Bs horizon). The cation exchange capacity (CEC) is highly saturated in exchangeable acidity: 86% in the A1 horizon. Ca2+ + Mg2+ saturation is very low (<10% in A1 and <1% in the subsoil). Liming and fertilization significantly increase soil pH, base cation saturation and decrease soil acidity, especially in the surface horizons. Bulk precipitation is dilute and acidic (pH 4.5); ion concentration of the precipitation greatly increases after passing through the tree canopy. Dry deposition is moderate and has values in the lower range reported for Europe. Nitrification produced large amounts of NO3- -N and H+ ions in the O layer and organomineral horizons. Nitrate and aluminium dominate the chemical composition of the soil seepage water. Liming induces a considerable rise in the soil solution pH and the base cations (Ca2+ + Mg2+ and decreases nitrate and aluminium substantially. Liming alone seems to lower the rate of nitrification. Addition of fertilizers increases the deep drainage of base cations which could reduce the long term efficiency of liming. Improvement of tree health-status accords with the positive effects of liming and/or fertilization on the soil's solid phase and solution.