INVESTIGATIONS ON THE SUCCESS OF SPRUCE P RUNING - A COMPARISON OF MANUAL AND CLIMBING MACHINE PRUNING WITH CONSIDERATION OF WOOD-BIOLOGICAL ASPECTS

The investigation describes the risks for the trees and the quality of pruning results if both hand pruning and pruning using climbing machi nes (KS31) is applied. The samples come from four stands in the Black Forest. The prunings date back 13 to 32 years. The average base diamet er (vertical) of the pruned branches is 16 mm, the maximum 18 mm. The remaining length of cut branches with 14 mm in the case of machine pru ning was greater than that achivied by careful hand pruning. Also the quality of the cuts is better when using hand saws. Nevertheless, the section necessary to heal over the cut wound, for both pruning techniq ues, is nearly the same. To heal over 90% of all wounds a total of 80 mm diameter growth has to rake place. Discolorations and ohter damages had no negative economic relevance. The positive results are only val id for Spruce grown under conventional stand conditions with small bra nch diameters.