Effects of mounding and soil clay content on postplanting success of Norway spruce

The results showed that mounding decreases early postplanting seedling mortality and increases growth, thus promoting plantation establishment on forest soils with varying soil textures. The mounding method or mound height showed no clear difference in seedling growth in the studied soils and years. Early postplanting seedling height growth and survival (three years from planting) were slightly and root-collar diameter a bit better related to the soil clay content; the seedling attributes tended to be poorest on silty soils with a clay content of 20-30% (or silt and fine sand content of over 60%), compared with coarser or finer (clayey) soils. The results suggest that even effective soil preparation cannot fully alleviate all of the inherent disadvantageous effects of sorted silty soils on early postplanting and later growth; but corroborative research is still needed.