Field Trials of the Forest Service Hardwood Tree Grades

A series of field trials were conducted on seven hardwood species to determine how well total lumber tally and value could be predicted by using the Forest Service Hardwood Tree Grades and companion lumber grade yield equations. Approximately 50 trees were selected for each trial. After the trees were measured, graded, and felled, the resulting logs were sawed into lumber which was graded and tallied. For each trial, the actual lumber volume differences for the 10 field trials ranged from -7.7 to .5 percent and averaged about 5 percent. Value differences ranged from -13.7 percent to .8 percent for nine of the trials and averaged about 6 percent. When standard lumber grades were sawed using recognized methods of hardwood lumber manufacture, actual and predicted lumber tally differed by 2 to 9 percent. Actual and predicted lumber value differed by as much as 14 percent. Actual value is sensitive to product mix and thickness patterns. If a sawmill deviates from producing standard lumber, the predicted lumber grade tallies will not apply, even though the total predicted tally may be accurate. Value prediction may be satisfactory, but some checking is recommended to verify it.

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