Compression wood – Programme summary

The term compression wood is used to describe the wood that tends to form in conifers on the underside of leaning stems, on the leeward side of trees exposed to strong winds, in crooked stems and in the lower part of trees growing on a slope. The structure and chemical composition of compression wood differs from that of normal wood. It can cause major problems in the wood processing industry, resulting in a deterioration in both mechanical properties and dimensional stability.

Darker compression wood revealed using transmitted light on a thin section.
Distortion caused by compression wood.

In 2000 the European Union approved funding for a shared-cost project under the Fifth Framework Programme, to increase knowledge of the way in which compression wood is formed with a view to linking raw material properties to the end product performance of construction wood.

Optically scanned image of disc cut from 45 year old Sitka spruce growing near the west coast of Scotland. Direction of prevailing wind is indicated by the arrow (ie wind flow is from left to right) and an area of severe compression wood is clearly visible on the leeward side of the disc.
(Photo courtesy of Franka Bruechert)
X-ray image of same disc illustrating density variations. The area of compression wood shows up clearly as the lighter coloured (denser wood) area on the leeward side of the disc.

The mechanisms of compression wood formation were studied along with the impact of site factors and silvicultural practices on its development and subsequent wood quality. The relationship between wood quality parameters and the properties of the end product was determined, in order to better meet the demands of the end user.

This research will help to integrate information about compression wood through the entire woodchain, from the primary forest production to the end user.

The output of the project is an advanced decision support tools in the form of predictive models linking silvicultural practice with raw material properties and the end product performance.