COMPARISON OF THE GRAVITATIONAL AND THE CAPILLARY WATER OF 3 SPRUCE (PICEA-ABIES KARST) STANDS IN THE VOSGES - USEFULNESS FOR THE IDENTIFICATION OF THE CURRENT SOIL FUNCTION AND CONSEQUENCES FOR THE HEALTH-STATUS OF THE STANDS

Comparison of the gravitational and the capillary water of 3 spruce (Picea abies Karst) stands in the Vosges. Usefulness for the identification of the current soil function and consequences for the health status of the stands. Soil solutions were studied for I yr in 3 Norway spruce stands (Picea abies Karst) in the Vosges mountains. These stands represent a gradient of production and forest decline symptoms for Spruce in this area: the Gemaingoutte stand has high production and never showed any decline symptoms; the Aubure stand is moderately productive but showed some decline symptoms; and the Bonhomme stand has a low productivity with high decline symptoms. in the latter a revitalization was obtained by fertilization (Ca and Mg). Gravitational water was collected every 2 weeks in Aubure and every fourth week at the other 2 sites, by zero-tension hysimeters installed at different depths in the soil profile (15, 30, 60 and 70 cm). Capillary water was extracted from soil samples collected at the same time interval, by displacement in columns. The results showed that these 2 types of solutions could have very different or sometimes similar compositions. It was hypothesized that both soil physical and climatic parameters determining the soil wafer regime, could explain these differences. The residence time and the wafer pathways are of paramount importance for the soil solution chemistry. In the studied soils, the observations made on the gravitational and capillary water (fig I to 5) allowed us: i) to identify the biogeochemical function of the soils (fig 6); ii) to qualify the transformations of soil biogeochemistry after liming (fig 4); and iii) to correlate the edaphic parameters to the health status of the stands (fig 7).