Figure 4

Stiffness variation within and between Douglas-fir trees, selected by acoustic time classes, for thinning treatments A, B, C, D, and E. Box plot whiskers extend to the most extreme data points, provided they are no more than 1.5 times the interquartile range from the box. Outliers, i.e. points outside the whiskers, are denoted by blue circles. Mean tree stiffness is denoted by ‘*’.