The Potential of Acoustics to Determine Family Differences for Wood Quality in a Loblolly Pine (Pinus taeda L.) Trial

Acoustics have been used to determine wood quality attributes in both standing timber and sawn lumber. Sonic transmission data are collected nondestructively and can act as a surrogate for stiffness, they are directly related to modulus of elasticity (MOE) and closely related to differences in microfibril angle (MFA). Together with wood density, MFA and MOE are the most important wood characteristics that affect solid wood properties. Breeding and selection for desirable wood properties will be a key factor in determining the global competitiveness of the forest industry in the United States. Breeders of loblolly pine (Pinus taeda L.) have been able to select for differences in wood specific gravity, MOE and MFA based on data collected from wood increment core samples. The use of acoustics in determining wood quality has merit in that it requires no direct wood sampling. However, before differences in acoustic transmission can be used in a breeding program, a number of questions need to be answered. Are there differences in transmission of sufficient magnitude and repeatability to allow heritable differences to be detected among families? How large a component is genotype by environment interaction? Is the equipment robust enough to be used by field crews and can data be collected efficiently? To answer these questions, the Southern Institute of Forest Genetics in collaboration with the Western Gulf Forest Tree Improvement Program collected acoustic velocity data using the Fakopp Stress Wave Timer in three controlpollinated loblolly pine progeny tests established by International Paper Company in southeast Texas. Sampled trees were disease free and without forks. Acoustic velocity was measured at two radial directions on each tree over a length of 1.2 m spanning breast height. Measurements were averaged for each tree. Variance components were estimated for each location using the software packages DIALL and DIALLC. Then single location heritabilities were calculated. Heritabilities for the averaged acoustic velocity were moderate yet large enough to be useful in an applied breeding program. Phenotypic correlations among these traits were small, but positive suggesting that selection for growth and stiffness can be done simultaneously. Field protocols, however, need to be further refined to avoid data outliers and to arrive at easier methods of collecting observations on the large numbers of trees required to estimate parental breeding values.