A NON-DESTRUCTIVE FIELD MEASUREMENT OF STEM MOE FOR EVALUATING WOOD QUALITY IN STANDING TIMBER

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This invesigation deals with a field instrument capable of determining the bending modulus of elasticity (MOE) in the stem of standing trees and the application of the instrument to some plantation grown Japanese larch stands.The MOE calculation is based upon the deflection of the stem. The bending moment is generated by a weight applied on a lever-arm attached to the stem. The deflection is detected by the middle-ordinate gage placed on the convex side of the bent stem.Results are summarized as: 1. The increase of MOE in larch trees was remarkable from 10 to 20 years of age, and thereafter it gradually became stable. 2.The MOE of the stems agreed well with laborarory tests on logs obtained from sample trees. 3. The MOE values of 136 stems at 13 larch stands were in the range of 60-150 t/cm^2. 4. The effect on MOE values by growth rate was little within a stand. The coefficient of variation for MOE in each stand was about 12%. 5. Differences of average MOEs between larch stands in the same area were found, which may have been due to local environmental condition such as slope exposure. 6. A test in a larch clone stand derived from 52 plus-trees did not show any superiority in MOE to the above mentioned larch stands, while the inter-clone deviation was little.The method proposed in this study may be utilized for the assessment of wood quality in live trees, the selection of trees for thinning cut and/or the selection of plus-trees from the wood quality viewpoint.