COMPARISON OF THE GRAVITATIONAL AND THE C APILLARY 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 (P icea abies Karst) stands in the Vosges. Usefulness for the identificat ion of the current soil function and consequences for the health statu s of the stands. Soil solutions were studied for I yr in 3 Norway spru ce stands (Picea abies Karst) in the Vosges mountains. These stands re present a gradient of production and forest decline symptoms for Spruc e in this area: the Gemaingoutte stand has high production and never s howed any decline symptoms; the Aubure stand is moderately productive but showed some decline symptoms; and the Bonhomme stand has a low pro ductivity with high decline symptoms. in the latter a revitalization w as obtained by fertilization (Ca and Mg). Gravitational water was coll ected every 2 weeks in Aubure and every fourth week at the other 2 sit es, by zero-tension hysimeters installed at different depths in the so il profile (15, 30, 60 and 70 cm). Capillary water was extracted from soil samples collected at the same time interval, by displacement in c olumns. 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 w afer regime, could explain these differences. The residence time and t he wafer pathways are of paramount importance for the soil solution ch emistry. In the studied soils, the observations made on the gravitatio nal and capillary water (fig I to 5) allowed us: i) to identify the bi ogeochemical function of the soils (fig 6); ii) to qualify the transfo rmations of soil biogeochemistry after liming (fig 4); and iii) to cor relate the edaphic parameters to the health status of the stands (fig 7).