Damage to Residual Stand Caused by Mechanized Selection Harvest in Uneven-Aged Picea abies Dominated Stands

Permanent field plots were established in two uneven-aged Norway spruce (Picea abies (L.) Karst) dominated stands in west-central Sweden. The objective was to quantify level and type of damage caused by harvesting and to quantify the difference between two treatments: T20) only skid road harvest (20 m distance between ca. 4 m wide roads), and T40) skid road harvest (40 m distance between ca. 4 m wide roads) combined with thinning between the roads. In T40, the goal was to harvest approximately the same standing volume as in T20. After harvest, two circular sample plots (radius 18 m, i.e. 1018 m(2)) were established at random locations within each treated area. All mechanical damage on the stem caused by harvest was measured and registered, including bark stripping larger than 15 cm(2), stem broken or split, and tearing of branches causing damage on the stem. About 70-90 per cent of the damaged trees were smaller than 15 cm dbh. Very few trees larger than 25 cm dbh were damaged. In T20, more than 50 per cent of the damaged trees were located less than 5 in from the skid road, compared to less than 25 per cent for T40, in which more than 50 per cent of the damaged trees were located 5-10 m from the skid road. Creating only half the number of skid roads caused no more damage, and was probably more profitable because mean stem volume was about 1.5 times larger than in T20.