The effect of mechanical site preparation methods on the establishment of Norway spruce (Picea abies (L.) Karst.) and Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) in southern Sweden

The aim of this study was to gain a deeper knowledge of the effects of mechanical site preparation on the survival and growth of Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) and Norway spruce (Picea abies (L.) Karst.) seedlings in southern Sweden. The experiment was conducted on a fresh clearcut at the Asa experimental forest (57 10 N). The effects of five different site preparation treatments were investigated: control, patch, mound, invert and mix. In each treatment, 40 seedlings of Norway spruce and 40 of Douglas fir were planted in each of four blocks. Site preparation had little or no effect on the survival and growth of Norway spruce: only a few seedlings died during the first 2 years. For Douglas fir, however, all site preparation treatments increased survival compared with the control, where mortality was high. The most intensive soil preparation treatment, mix, significantly increased root growth and total biomass. Pine weevils caused more severe damage to Douglas fir seedlings than to Norway spruce and targeted different locations in the two species, causing comparatively more damage to the leading shoots of Douglas fir seedlings.