Long-term effect of site preparation on soil quality in Tuntsa, Finnish Lapland

Abstract

Long-term effects of mechanical site preparation on soil chemical properties of Norway spruce (Picea abies) clearcut areas have remained unclear. In 1960 a forest fire burned a Norway spruce forest in Finnish Lapland and the remaining trees were harvested. Subsequent mechanical preparation with disk trenching created continuous cross-contour disturbance tracks. We measured soil dielectric permittivity as dependent on water content, electrical conductivity, temperature, pH, as well as ammonium acetate extractable concentrations of mineral soil elements in a clearcut area. After forty-six years the loss of soil nutrients was considerably high, particularly with exchangeable Ca (−40%) and Mg (−51%), Ca:Al ratio (−57%), and soil electrical conductivity (−53%). The disk trenching had no considerable long-term effect on soil water content. The results indicate that intensive mechanical site preparation is a risk for long-term soil fertility and forest productivity in boreal conifer stands.