Assessment of intensive stress-wave scanning of Douglas-fir trees for predicting lumber MOE

The purpose of this study was to determine whether intensive stress-wave scanning of standing trees could predict the modulus of elasticity (MOE) of lumber sawn from those trees. Twenty-four Douglas-fir trees were selected for this study. Twelve longitudinal and eight transverse stress-wave velocity measurements were made on each tree. Once scanned, the trees were felled, and a 16.5-foot (5.0-m) butt log from each tree was sawn into 2 by 6 lumber. The lumber was air-dried to a uniform MC and planed to American Lumber Standards size. Dynamic MOE was measured with a Metrigard Model 340 E-computer, and visual grades were assigned by a Western Wood Products Association lumber inspector. Regression analysis showed that the coefficient of determination (r2) for average (12 measurements) longitudinal stress-wave velocity and average dynamic MOE for lumber was 0.466. The coefficient of determination for average (8 measurements) transverse stress-wave velocity and average dynamic MOE for lumber was 0.495. Correlation values were somewhat higher when index values combining average longitudinal and average transverse stress-wave velocities (20 measurements) were compared to average dynamic MOE for lumber (r2 = 0.591). Additionally, coefficient of determination values for index values and average dynamic MOE for lumber were highest (r2 = 0.839) for the seven trees with the least variation in lumber grade and were lowest (r2 = 0.366) for the seven trees with the most variation in lumber grade. Results indicate that intensive stress-wave scanning of Douglas-fir trees can improve the prediction of dynamic MOE of lumber sawn from the trees. However, high correlation was achieved in only those trees with little variation in lumber MOE and grade.

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