Standing spruce volume

Several studies show that the amount of mature spruce is an important predictor of tree mortality caused by Ips typographus during outbreaks. In areas with large volumes of mature, harvestable spruce, a greater proportion of the spruce forest is damaged by bark beetle attacks. This relationship was demonstrated during the outbreaks in Norway in the 1970’s and in southern Sweden after the Gudrun storm in 2005.

Different bark beetle species attack spruce trees with different bark thicknesses, and Ips typographus prefers a bark thickness that is common on medium-sized to mature spruce trees. The map “Mengde granskog” shows the proportion of individual square kilometer pixels that is dominated by production forest of spruce. Specifically, the green shading shows the percentage of each pixel (in quartiles) that has >5 m³ Norway spruce per hectare. See “Tegnforklaring” at the top of the menu for details.