Abstract:

Stress wave method was used to test forty Hankow Willow（Salix matsudana）roadside trees in Northeast Forestry University and two dimension images and wave velocity matrix of 120 slices of cross sections in sample trees were obtained and analyzed. According to these images, the inner structure of cross section in standing tree is divided into four categories: non-defect, heart rot, sapwood rot, heart rot and sapwood rot. Further analysis results showed that the radial propagation velocity in healthy standing trees was the fastest and the change of wave velocity from one sensor to other sensors clockwise exhibited a trend from initial increase to decrease. However, the inner decay of standing trees could cause the decrease of propagation velocity of stress wave, and the analysis also showed that the curve of wave velocity change would not be a trend from initial increase to decrease but change into a flat curve in standing trees with heart rot. Thus, it was potential to assess inner decay of standing trees depending on the change of wave velocity. Additionally, it could identify the area and positions of decay of stress wave detection, and could evaluate the stability of Hankow Willow roadside trees according to t/R value of cross sections.

Key words: stress wave, standing tree, testing, stability assessment