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Defects in Properties of wood are used as common indicators for grading logs. In this
-study, the logs of various woody species from ten different forestry projects have been evaluated based on their measured defects.
The results of this study showed that the average diameter of acceptable knot for the first 3 meters of the trunks was 2.8 cm for maple (the least value) and 7 cm for hornbeam (the highest value), respectively. Moreover, the knotless portion of the first 10-meter-Iong trunks were 12.2, 32.4 and 20 percent for hornbeam, elm and beech, respectively. As for pith decay of trunk, the least and the highest values were 56 and 84 percent which were associated with maple and elm, respectively. As for trunks with bent defect, oak and basswood showed the lowest value (7 percent), while hornbeam showed the highest value (18 percent). This value for beech was about 10 percent. Bole taper (decrease of bole diameter of less than 2 cm per meter of length) was 65 percent in maple (the lowest value), and 96 percent in oak (the highest value). This value for beech was 75 percent. The lowest and highest values for defect of interlocked fibers were observed in boles of alder (68 percent) and oak (91 percent), respectively. The percentage of boles with interlocked fibers for beech was 89 percent. As for trunk with irregular annual ring, it was shown that hornbeam had the lowest value (82 percent). However, 94 percent of the other woody species didn't show such a defect. Finally, the lowest and highest percentage valu_s--for trunks with abnormal annual ring_ were 16.1 and 24.3 for oak and elm species, respectively.