Early growth of planted Norway spruce and Scots pine after site preparation in Sweden

Norway spruce (Picea abies (L.) H. Karst) and Scots pine (Pinus sylvestris L.) have different site preferences, but silvicultural recommendations for their regeneration at planting (including site preparation) are often the same. Thus, there is a clear need for greater understanding of species-specific interactions between site preparation and site properties. To meet this need, the species' growth and survival have been monitored at both fertile and poor sites in northern and southern Sweden. At each of these sites, effects of three types of site preparation - removed humus (RH), deep soil cultivation (DSC) and control (C, no site preparation) - were compared. Results show that Scots pine grew more rapidly initially than Norway spruce, and DSC site preparation promoted growth of both species. However, on poor sites there was a delay in growth responses. In addition, removal of organic material in the RH treatment caused a sustained growth check of Norway spruce, but not for Scots pine. This study confirms that it is beneficial to use site preparation as it increases the survival of both species and may increase growth. However, site preparation methods that reduce the amount of organic material in the planting spots should be avoided for Norway spruce.