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Injuries and mortality to advance growth (saplings) after selection harvesting was studied in 17 multistoried Norway spruce (Picea abies (L.) Karst.) stands. Harvest removals ranged from 33 to 67% of initial basal area. Four of the stands were harvested with a motor-manual method (chain saw and skidding with farm tractors; M-FT). The remaining stands were harvested with single-grip harvesters and forwarders (H-FW). In each stand, injury rates were evaluated on a 24 × 48 m plot, located between the centre lines of two parallel strip roads that were spaced 24 m apart. All logging teams had at least 5 years of experience in clear-cutting and thinning operations. The trees to be removed and the strip road centre lines were marked prior to harvest. Mortality varied from 5 to 51%, whereas total injury (injured + dead saplings) varied from 17 to 76%. Mortality and injury levels were generally highest on H-FW plots. Crown reduction and leaning stems were the most frequent types of injury, regardless of operating method. Injury rates increased with sapling height with the H-FW method, whereas the opposite was found on M-FT plots. Saplings without preharvest damage in the form of top or leader defects had a higher probability of being injured than saplings with such damage in stands harvested with the M-FT method. A similar difference was not found on H-FW plots. A logistic regression model shows that the spatial risk of injury depends on the interaction between forest condition factors and operational characteristics. Forest condition factors influencing the risk of injury are sapling height and the location of saplings relative to larger residual trees and strip roads. Corresponding operational characteristics are operating method and harvest intensity.Résumé : Les blessures à la régénération préétablie (gaules) suite à une coupe sélective ont été étudiées dans 17 peuplements inéquiennes d'épicéa commun (Picea abies (L.) Karst.). Le prélèvement variait de 33 à 67% de la surface terrière initiale. Quatre peuplements ont été récoltés de façon partiellement mécanisée (scie à chaîne et débardage avec des tracteurs de ferme). Les autres peuplements ont été récoltés avec des engins multifonctionnels et des porteurs. Dans chaque peuplement, le taux de blessures a été évalué dans une parcelle de 24 × 48 m, située entre les lignes de centre de deux chemins de débardage parallèles espacés de 24 m. Toutes les équipes d'opérateurs avaient au moins 5 ans d'expérience dans les coupes d'éclaircie. Les arbres à enlever et les chemins de débardage avaient été marqués avant la coupe. Le taux de blessures (gaulis tués ou blessés), qui variait de 17 à 76%, était généralement plus élevé dans les parcelles où la récolte était entièrement mécanisée. Les gaulis qui n'étaient pas endommagés avant la récolte, par la présence de défauts soit dans la tête, soit à la pousse terminale, avaient une plus forte probabilité d'être endommagés que les gaulis qui avaient de tels dommages dans les peuplements récoltés de façon partiellement mécanisée. Un mod...

The operational ef® ciency of single-tree and group selection with a single-grip harvester was studied in uneven-aged spruce forests at high altitudes in southern Norway. Three harvest intensities of single-tree selection and two group sizes were examined in group selection. Single-tree selection included harvest intensities of 25, 45 and 65% of basal area. Group sizes for group selection were 0.063 and 0.250 ha. Normally, single-tree selection is considered less ef® cient than group selection or clear-cutting. In this study, because time consumption per cubic metre was primarily dependent upon average harvested tree volume, the large harvested tree size for single-tree selection allowed this treatment to be more ef® cient than group selection. The two blocks in this study were part of a larger design of ® ve blocks with identical treatments under varying stand conditions. The relative operational ef® ciency of single-tree selection compared with group selection was greatest in stands of low stocking. Other studies have also shown that mechanical damage to the residual stand is lowest under these conditions.

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