Non-destructive diagnosis of wood decay in larch trees using a stress wave velocity measurement : case studies in the research forests of Kyushu and Shinshu Universities

Abstract

Stress-wave velocity of the trunk in the transverse direction was investigated in 50-year old Larix kaempferi stands in the research forests of Kyushu and Shinshu Universities. The frequency distribution of stress-wave velocity classes of sound trees was normally distributed. However, because the stress-wave velocities of decayed trees were lower than those of sound trees, the stress-wave velocity classes exhibited a J-shaped frequency distribution in stands with decayed trees. The slope of the linear regression between the percentage of the decayed portion along the diameter of the trunk and stress-wave velocity (km・s^-1) ranged from -0.011 to -0.015. The y-intercept of the linear regression conformed to the average of the stress-wave velocity of sound trees. These findings provide effective information in diagnosing wood decay using stress-wave velocity measurements.