Increment and decay in Norway spruce and Scots pine after artificial logging damage

The effects of depth, size, location, and season of artificial logging damage on increment and decay of Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) trees were studied in Iona-term experiments in central Finland. Damage types applied were root damage, root collar damage, increment borer hole, and stem damage. In root collar and stem damages, two sizes (100 or 400 cm 2) and depths (shallow or deep) were applied. Five to 20 years after damaging, the damages did not result in a decrease in radial, height, or volume increment. In Norway spruce, the frequency of decay in the root collar and stem damages was high. From large and deep damages, decay spread faster than from smaller and shallow ones. In Scots pine, a lower proportion of trees were decayed compared with Norway spruce. Increment coring resulted in decay in most of the trees, but the decay spread slowly. The effect of compass direction or the month of damaging was negligible. The most common decay fungus in Norway spruce was Stereum sanguinolentum (Alb. & Schwein. Fr.:) Fr. In Scots pine, only nondecay fungi were isolated. In general, logging damages decreased sawlog production through the rejection of butt logs containing decay or discoloration.