Effects of delayed regeneration and slash removal 30 years after establishment of Norway spruce

Treatments done in the regeneration phase significantly affect seedling growth and survival. Postponing regeneration up to four years after clearfelling can reduce seedling damage and mortality caused by pine weevils (Hylobius abietis). However, under delayed establishment, competing vegetation can colonize the site, possibly reducing seedling growth. Slash removal after clearfelling can facilitate later regeneration treatments such as site preparation and planting, increasing planted seedlings’ survival. But slash removal can also reduce long-term stand growth, due to nutrient removal from the site. In this study, the long-term effects of clearcut age and slash removal on volume production was evaluated 30-years after planting Norway spruce. Data was collected from a long-term experiment established between 1989 and 1993. The experiment included four sites in southern Sweden. At each site, a clearcut was made every year from 1989 to 1993. To study the slash-removal effect, slash was retained on half of the clearcut area and removed from the other half. To study the effect of clearcut age, clearcuts were planted each subsequent year until the end of the experiment, creating five different clearcut ages. Clearcut ages were compared when they had reached the same age. For the 1500 largest trees per hectare, the total volume significantly differed among clearcut ages. The youngest clearcut age had higher total volume than the oldest. There was also a significant difference between slash treatments, where slash removal lowered total volume compared to slash retention. However, delaying regeneration treatments caused a larger total volume loss than slash removal. • Clearcut age had an effect on total volume production. • Younger clearcut ages had higher total volume than the oldest clearcut age. • Total volume significantly differed between slash treatments. • Slash removal lowered total volume compared to retaining slash. • The effects were evaluated 30-years after planting Norway spruce.