In situ wood quality assessment in interior spruce

Abstract

Wood quality is of great importance for end-users but the concurrent conventional selection approaches targeted for growth rate are often associated with its decrease. The inclusion of wood quality into breeding programs requires finding a fast and inexpensive method that is capable of providing reasonably accurate estimates of wood quality attributes on standing trees without their significant injury during data collection. In the present study, wood density as the best single predictor of wood quality was estimated through drilling resistance using Resistograph IML F300; dynamic modulus of elasticity (MoEd) representing an important wood mechanical parameter was calculated from sound velocity measured by Director ST300™. Twenty-five open-pollinated families of 37- and 38-year-old interior spruce (the complex of white spruce (Picea glauca (Moench) Voss), Engelmann spruce (Picea engelmannii Parry), and their hybrids) growing on three sites (1,146 trees) were included in this study. Narrow sense heritabilities and phenotypic and genetic correlations were estimated for growth (height, diameter at breast height, and volume) and wood quality attributes (overall x-ray density, x-ray density of the first 15 rings, resistograph-based density, earlywood density, latewood density, latewood proportion, acoustic velocity, and MoEd). Phenotypic and genetic correlations were strongly related (correlation of 0.85 based on the Mantel test). As anticipated for interior spruce, growth traits were negatively correlated with wood density, but surprisingly not with MoEd. It suggests that in interior spruce selection for rapid growth would result in wood density reduction while MoE would remain unaffected, pointing at a low usefulness of MoE’s inclusion among the selection criteria. The Resistograph provided a reliable estimate of wood density of the whole profile (0.59 and 0.84 for phenotypic and genetic correlations, respectively) as well as of the first 15 rings (0.60 and 0.95, respectively) and thus demonstrated its suitability for testing young trees. Although the heritabilities for the wood quality attributes estimated by x-ray were mainly moderate (0.17–0.26), the heritability of resistograph-based density was low (0.15). The heritabilities for other traits were low to moderate. The Resistograph appears to be a reliable non-destructive tool for in situ wood density assessment in interior spruce.