While volume is the single most important factor in determining the value of a stand of timber, the quality of the trees is nearly as important. To this end, a number of factors can cause trees to have “defects,” and therefore lower values.
Common Timber Defects
Put plainly, a defect can be defines as an imperfection in the slab zone, quality zone, or heart center resulting in the reduction of sound wood volume and quality. Though often times different defects can appear similar, the degree to which value is affected can differ drastically.
The most common defect visible in a standing tree is called a bark distortion. Bark distortions can be the result of mechanical wounds, holes, ingrown bark, bird peck and overgrown knots.Bark distortion can occur in three classes: light, medium, and heavy. Generally, light bark distortion consisting of a simple horizontal break is not a grading defect as it is located deep within the quality or heart section of the wood. Medium and heavy distortions are grading defects and result in a reduction in the volume of high-quality saw lumber. It is a common misconception that limbs are the only significant factor affecting standing timber grades, however bark distortions, while not limbs themselves, are often just as degrading.
Another common defect is bird peck. This is caused by various species of woodpecker eating insects and larvae found in the cambium of many hardwood tree species.
In veneer logs, epicormic branches are considered a major defect and prevent a tree from being suitable for most types of veneering.It is important to make a distinction in fresh birdpeck as opposed to heavy birdpeck or birdpeck that spans multiple seasons. While light birdpeck doesn’t detract from the value of a tree, heavy birdpeck causes stain and undesirable features across most species. The exception being members of the Hickory genus which develop a distinct purple stain as the result of even light birdpeck.
The final defect we will discuss in this blogpost is epicormic branches. These are clusters of buds and small stems that shoot out of the main trunk of a tree. This defect is common among many members of the Oak genus.
Underlying the epicormic branch scar is a knot surrounded by numerous tiny twig knots and possibly small bark pockets. The epicormic branch knot may not penetrate deeply into the wood. However, these epicormic branches along with the bud clusters may develop at intervals throughout the life of the tree and then become overgrown so that the defects they cause are found at several to many localities within the bole. Adventitious bud clusters and epicormic branches can develop independently of each other.
In veneer logs, epicormic branches are considered a major defect and prevent a tree from being suitable for most types of veneering.To a large degree, the impact to the value of a tree caused by a given defect is largely determined by how long the defect has been in place. Be it scars, wounds or bird peck, in general, the longer the defect has been affecting the tree the greater the impact to the value of the tree will be.