Fig. 2

Mean of the total length, number, and average length of surface checks for each sample group. Asterisks show significant differences between timber 1 and timber 4 (from different source heights) within cultivars using a paired t test (***P < 0.001, **P < 0.01, *P < 0.05). End-surface checks and center-surface checks shorter than 100 mm and longer than 100 mm were separated for the total length and number of surface checks