Relating Breast-Height Wood Properties to Whole-Stem Wood Properties in Loblolly Pine

Abstract

Prediction models describing the relationship between breast-height wood properties (wood density, α-cellulose content, and lignin content) and whole-stem wood properties were developed for juvenile and mature loblolly pine. Both genetic and environmental effects were examined when predicting whole-stem wood properties in juvenile loblolly pine. Also, the relationship between juvenile, transition, and mature wood properties and whole-stem wood properties were analyzed in both juvenile and mature loblolly pine. The juvenile trees used in this study were made up of 24 trees; 4 clones, 3 ramets per clone, replicated over two sites. The mature trees sampled in this study were 20 unrelated 20-year-old trees.

For juvenile loblolly pine, significant differences in all growth and wood property traits, excluding breast-height transition wood lignin content, breast-height juvenile α-cellulose content, and breast-height transition wood α-cellulose content were found between sites. At the Florida and Alabama sites, mean breast-height wood density values were 479.75 ± 8.27 and 424.37 ± 7.23 kg⁄m3, respectively. Across both sites, mean breast-height wood density values were 450.86 ± 7.96 kg&⁄m3. Mean whole-stem values were 383.66 ± 4.29 and 429.27 ± 7.74 kg⁄m3 at the Alabama and Florida sites respectively. At the Alabama site, mean breast-height α-cellulose content was 42.12 ± .23%, while mean breast-height α-cellulose content at the Florida site was 42.94 ± .21%. Mean whole-stem α-cellulose content at the Florida site was 41.89 ± .18% and mean whole-stem α-cellulose content at the Alabama site was 41.25 ± .22%. Also, at the Florida and Alabama sites mean breast-height lignin content values were 27.10 ± .17% and 28.22 ± .22%, respectively. Calculated mean whole-stem lignin content was 27.21 ± .15% at the Florida site and 28.59 ± .13% at the Alabama site. No significant clonal differences were found for any trait except breast-height juvenile wood α-cellulose content and height. Both linear and polynomial models were developed for describing the relationship between breast-height wood properties and whole-stem wood properties. Coefficients of determination for wood density ranged from 0.72 to 0.92 when data from both sites were combined. Across sites, coefficients of determination ranged from 0.43 to 0.73 for α-cellulose and 0.58 to 0.82 for lignin content. Correlations between breast-height wood properties and whole-stem wood properties were high and ranged from 0.84 to 0.92. Significant correlations were also found between breast-height juvenile and transition wood properties and whole-stem wood properties. However, the best predictor of whole-stem wood properties proved to be the entire breast-height pith to bark sample.

For mature loblolly pine, both linear models were developed that described the relationship between breast-height wood properties and whole-stem wood properties. In mature loblolly pine, mean breast-height wood density was 455.25 ± 4.15 kg⁄m3 and mean whole-stem wood density values was 414.52 ± 4.18 kg⁄m3. Mean breast-height α-cellulose yield was 41.1 ± .22 % and mean whole-stem α-cellulose yield was 40.77 ± .20 %. Mean breast-height lignin content was 27.94 ± .14 % while mean whole-stem lignin content was 28.41 ± .12 %. On average, breast-height lignin content was about 0.47 % lower than whole-stem lignin content. Coefficients of determination for wood density ranged from 0.27 to 0.85. Coefficients of determination ranged from 0.42 to 0.95 and 0.59 to 0.85 for α-cellulose and lignin content respectively. For juvenile wood, correlations between breast-height wood properties and whole-stem wood properties ranged from 0.62 to 0.92 and correlations with whole-stem wood properties ranged from 0.77 to 0.90 for breast-height transition wood and from 0.44 to 0.84 for mature wood. Positive correlations were found between lignin measurements and growth measurements (0.12 to 0.24). For mature loblolly pine, the entire breast-height sample was the best predictor of whole-stem wood properties. Depending upon the trait of interest, breast-height transition wood also was an adequate predictor when compared to juvenile and mature wood.