SILVICULTURAL USE OF WOOD ASHES - EFFECTS ON THE NUTRIENT AND HEAVY-METAL BALANCE IN A PINE (PINUS-SYLVESTRIS, L) FOREST SOIL

In a sustainable forestry recirculation of nutrients through the appli cation of ashes from forest residues can be an essential way to guaran tee healthy and vital forests. Wood ashes can also be regarded as a me asure against soil acidification. Wood ashes were applied at various r ates to the soil in a 35 years old pine (Pinus sylvestris, L) stand at Ringamala in Blekinge, South Sweden. The experiments started in 1984. The different treatments gave a clear effect on soil chemistry with d ecreased acidity and aluminum ion concentrations. The base saturation increased in both mor and upper mineral soil layers. Generally no sign ificant increases were found in soil concentrations of heavy metals, e xcept for Cu which increased significantly in the mor layer. Also the extractable Mn concentration increased, in spite of the increased pH i n the soil after application of ashes. In order to achieve a biologica l circulation of nutrients through ash application without polluting t he environment, it is of ultimate importance that the wood chips used in power plants and other furnaces have a low concentration of heavy m etals and other pollutants.