Selection for cellulose content, specific gravity, and volume in young Populus deltoides clones

Seventy-five eastern Cottonwood (Populusdeltoides Bartr.) clones, selected from tests representing the top one-third of clones tested throughout the Lower Mississippi River Valley, were analyzed for alpha cellulose content, specific gravity, and volume after three growing seasons. All traits were found to differ significantly among clones. Mean clonal alpha cellulose content ranged from 48.2 to 55.8% of oven-dry, extractive-free wood with an average of 51.1%. Specific gravity averaged 0.33, with clones ranging from 0.27 to 0.39. Specific gravity was highly inherited, while alpha cellulose content was found to be moderately heritable. Negative genetic correlations between volume and both wood properties indicate that using a selection index to simultaneously improve all three traits is currently not possible. Two other selection methods were discussed. These selections showed substantial gain differentials in volume, but either a small loss or improvement in specific gravity and alpha cellulose content. This indicates that at age 3 years only volume should be considered in a selection program.