Effekt av markberedning, næringsstatus og kortdagsbehandling ved planting av gran (Picea abies)

Planting after clearcutting is the most common establishment method when establishing Norway spruce (Picea abies) in Norwegian forestry, and during 2015 it was planted about 31,3 mill. seedlings, distributed on 17 200 ha. Regeneration after clearcutting is mandated through Forestry act and land owners in Norway are therefore obliged to ensure this within three years after final cutting. Establishment success and development of Norway spruce seedlings depends on several factors and the main purpose of this experiment was therefore to investigate how seedlings react and develop due to different treatments. In late May, 2015, 772 two-year old containerized Norway spruce seedlings with six different treatments were planted on a fairly high site-index site (G17) in Kongsvinger municipality, Hedmark county in Norway. The treatments were consisted of three different factors, high and low nutrient status from the nursery, short-day treatment/non short-day treatment and soil scarification/non soil scarification. Four registrations were conducted periodically from May to October 2015 with recordings of height and diameter-development, damaged caused by pine weevil (Hylobius abietis L.) and browsing mammals, and the annual amount of dead seedlings. Together with the last registration in October, 108 plants were harvested for further studies of nutrients and biomass together with 36 root samples for studies of root-growth. Seedlings with high nutrient status from the nursery had the highest growth in terms of height, diameter and biomass compared to seedlings with low-nutrient status, but no such difference could be detected for the amount of nutrients in twigs or needles. According to my results short-day treated seedlings did not differ from seedlings without short-day treatment in terms of increased growth or nutrient content. This experiment could therefore only proof differences in seedlings development due to differences in nutrient status before planting. Effects of soil scarification increasing root-growth could not be detected in our study, however seedlings planted in mineral soil had the smallest amount of damages caused by pine-weevil although this effect only was significant for seedlings with high nutrient status. Seedlings with high nutrient status were also found to be most affected by mammals. These results suggest that seedlings with higher nutrient status before planting has the best assumptions for quicker growth and higher establishment success but are also more desirable to mammals. Even though seedlings with lower nutrient-status had slower growth they seem to equalize the differences throughout the first growing-season, in addition to be less affected by pine-weevils and mammals