Rehabilitering av degenererad skog i kärvt klimat: utvärdering av ett 31-årigt experiment på Ätnarova försökspark

Different silvicultural alternatives for treatment of a degenerated forest in harsh climate (67°N, 460 m a.s.l.) were investigated in a field trial established in 1983/84 with 32 parcels à 0.1 ha. The initial stand was about 100 years old and kept the stem volume 50 m³ with 40 % Norway spruce and 60 % downy birch. It grew about 1 m³ per hectare and year in the observation period. Clearcutting without regeneration measures gave a lot of birch sprouts and few spruce seedlings and was assumed to reshape the initial stand in the long run. Seed trees of spruce gave more spruce seedlings than “no measures” but the seedlings grew slowly. Scarification beneath the seed trees had no significant effect. Planting below birch shelters led for Scots pine and lodgepole pine to very high mortality and for Norway spruce to heavily restricted growth. Planting lodgepole pine after clear-cut gave fast-growing trees but also high mortality and heavy snow damages. Planted Scots pine after clear-cut had a better survival rate and was judged capable to form acceptable stands in the future. Planted spruce after clear-cut developed well, especially after chemical killing of the birch stumps. Site indices of plantations on clear-cuts were 20–23 m, indicating a potential productivity of above 4 m³. The rehabilitation of the degenerated initial stand by clear-cutting and planting seems thus to be successful. With support of observations also in neighboring trials and stands, planting of Scots pine is supposed to be the most profitable silvicultural alternative.