Acoustic Evaluation of Thinning and Biosolid Fertilization Effects on Wood Quality of a Douglas-fir stand

Abstract

In this study, we examined the potential of using a time-of-flight (TOF) acoustic wave method to evaluate thinning and biosolid fertilization effects on acoustic velocity of trees and modulus of elasticity (MOE) of structural lumber in a 76-year-old Douglas-fir (Pseudotsuga menziesii, (Mirb., Franco)) experimental stand. The stand consisted of four treatments: control, thinned, biosolid fertilized, and a combined thinned and fertilized treatment, each with three replicates on 0.08 hectare plots. Four trees were selected in each plot using a stratified random sample based on the plot quadratic mean diameter, resulting in a total sample of 48 trees ranging from 14.2- to 53.3-cm diameter at breast height (DBH). The sample trees were first nondestructively tested using a TOF-based acoustic measurement system to obtain acoustic velocity in trees. The sampled trees were then harvested, bucked into merchantable-length stems and then milllength logs that were sawn into lumber. Acoustic velocities of stems and logs and MOE of lumber were subsequently obtained. Our results indicated that biosolid fertilization had a statistically significant effect on acoustic velocities of trees, stems, and butt logs; thinning did not have a statistically significant effect on acoustic velocities; combining thinning with biosolids did not produce a change in acoustic velocity different from applying biosolids alone. These findings are consistent with the treatment effects that were reported on interannual ring specific gravity. At tree level, treatment had no significant effect on lumber stiffness.

Citation

Wang, Xiping; Ross, Robert J.; Verrill, Steve; Lowell, Eini; Barbour, Jamie. 2015. Acoustic Evaluation of Thinning and Biosolid Fertilization Effects on Wood Quality of a Douglas-fir stand. USDA Forest Service, Forest Products Laboratory, General Technical Report, FPL-GTR-239, 2015; pp. 365-377.