Exterior Defect Indicators and Their Associated Interior Defect in Sugar Maple

Exterior defects in 90 sugar maple trees were identified, measured, and photographed. The association between each surface abnormality and an interior defect was determined by sawing the logs through-and-through and studying the variation in the percentage of association with respect to the size of the indicator, the height of the indicator about the stump, and the DBH, age, and growth rate of the tree. Interior defects were associated with 100 percent of the knots; 83 to 96 percent of the surface rises, bumps, and overgrown knots; 66 percent of the overgrown seams and bark distortions; 58 percent of the epicormic branches; and 49 percent of the flutes. The percentage of flutes with associated interior defects increased as flute length increased. The percentage of bark distortions and surface rises associated with interior defects increased as the height of the indicator above the stump increased. The interior defects associated with surface rises and bark distortion were closer to the tree surface with increasing height above stump, and thus were more likely to be in the quality zone. As tree age increased, the percentage of distortion and flutes associated with interior defects increased, and the percentage of overgrown seams associated with interior defects decreased. The correlations between number of bark distortions, flutes, epicormic branches, surface rises, and overgrown seams and tree age and growth rate were statistically significant. The number of bark distortions and flutes per tree increased as growth rate increased. Thus, growth rate is important not only in respect to wood volume produced but also to wood quality. Knowing the relative importance of defect indicator types by frequency of occurrence, percentage of associated interior defects, and the relationship of these frequencies and percentages to height above the stump will allow developing. prediction equations. These equations can be used to predict yields for a single product per tree, such as lumber or clear cuttings. Further data of this sort should allow segregation of stem portions into product classes, and predictions of yields within classes may be possible.

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