MEASURING THE PROPERTIES OF STANDING TREES WITH STRESS WAVES .3. EVALUATING THE PROPERTIES OF STANDING TREES FOR SOME FOREST STANDS

The properties of standing sugi (CryPtomeria japonica D. Don.) trees in some forest stands at different locations and different ages were measured with stress waves as described in our previous report.1/2) By means of small specimens we examined two factors that affected propagation times (DELTA T) of stress waves: namely, free water and the wood densities of standing trees, because the moisture content (MC) level of standing trees is always very high. We also showed that the propagation velocities (v) of stress waves gave the possibility of evaluating the properties of standing trees. The results are summarized as follows: (1) As a large correlation coefficient between Young's moduli (E) of small specimens in green conditions and at nearly 20% MC was recognized, we could compare the values of E of ''standing trees''. (2) We could confirm that there were differences between the values of E in some forest stands at different locations and of different ages. (3) When we made a simple linear regression line between the squares of v and E that went through the origin, the coefficients of determination were large for each forest stand. Thus the density, calculated from the regression coefficient, for each forest stand could be estimated as a constant value. (4) We obtained a similar trend for E from the v of stress waves. Thus we could use the v of stress waves instead of E as a new index for the properties of standing trees.