Damage to Picea abies Regeneration After Final Cutting of Shelterwood with Single- and Double-grip Harvester Systems
Logging-related damage to forest regeneration is a problem during final cutting in the shelterwood system. In order to compare the effects of logging methods, damage to natural Norway spruce [Picea abies (L.) Karst.] regeneration caused by single- (SGH) and double-grip harvester (DGH) systems was studied in three shelterwoods (132–234 m3 ob ha-1) in Sweden. Between 38 and 65% of the original seedlings (6 400–25 400 ha-1) were dead, had disappeared or were damaged after the final cutting. Regarding the damaged seedlings, 6–25% were mildly, 17–27% moderately and 48–76% seriously damaged. There were no significant differences between the SGH and the DGH systems concerning the frequency, severity, type or cause of damage to the regeneration. The proportion of damaged seedlings increased with increasing stem volume of the shelterwoods. Hence, stem volume ha-1 might be more important than harvester system for the proportion of damaged seedlings. The main conclusion is that final cutting of shelterwood can be done with both SGH and DGH systems with an acceptable amount of damage in a Norway spruce regeneration if the stand holds less than 200 m3 ob and 200 stems ha-1 and there are at least 6 500 seedlings ha-1 initially, with an average height of 1–2 m.