Injuries After Selection Harvesting in Multi-Stored Spruce Stands – The Influence of Operating Systems and Harvest Intensity

Abstract Mechanical injuries were examined after singletree selection harvesting in multi-storied stands of Norway spruce. Randomised block studies were used to compare the effect of two operating systems and three harvest intensities upon the injury rate to the residual stand. The average injury rate for mechanised shortwood harvesting was higher than for motor-manual cutting and cable skidding. The largest differences between these two systems were found at high harvest intensities in densely stocked stands. A number of variables were used to quantify this interaction. The variable which best explained the risk for injury in the individual stand was the ratio between removed vertical crown projection and horizontal crown-free projection before harvest. The higher injury rate for mechanised harvesting is attributed to the greater proportion of the stand which is impacted by the handling of trees.