On upland plateaus of the Belgian Ardenne, some hydromorphic soils are qualified as ‘white clays soils’. Maintaining coniferous forest production on these sites is brought more and more into question because of a series of silvicultural (wind instability, limited productivity, complicated harvesting, delicate regeneration) as well as environmental (degradation of soils, waters and habitats) potential problems. Because the term ‘white clays’ encompasses in fact a great soil diversity, the main objectives of this research are to caracterize the range of sites in terms of functioning and potentialities, and to propose relevant management strategies for each type.