Color variability of paper birch (Betula papyrifera Marsh.) wood at the tree level was examined in this article. Tree age, dimension, and vigor were expected to influence the proportion of discolored wood in paper birch boards; older, larger, and less vigorous trees were assumed to produce boards with higher proportions of discolored wood. The color analysis was performed on approximately 2250 boards produced from 168 paper birch trees harvested in two different stands from which only logs of sawing quality were used. An industrial scanner was used to digitize the boards and obtain colorimetric information. Results show that tree diameter and vigor significantly influenced the proportion of discolored wood in boards, whereas the effect of tree age did not have a significant influence in the model. An average area of 32.4% of discolored wood was obtained when considering all boards. Less vigorous trees showed a mean area of 45.32%, whereas middle-vigor and most-vigorous trees had mean areas of 30.78 and 15.47%, respectively. The colorimetric values were mainly affected by tree age and diameter, but these effects were variable for every colorimetric parameter. The analysis of the random effects demonstrated that most of the total random variance of the dependent factors came from the between-board, between-tree, and, to a lesser extent, between-log variation. These findings suggest that favoring shorter rotations would help produce trees with lower proportions of discolored wood
