Abstract:

To screen superior Populus deltoides clones for pulpwood plantation, the paper took 5 Populus deltoides clones, including 4 newly hybridized and selected clones and ‘Clone 69’ (P. deltoides Bartr. cv. ‘Lux’), as research objects, determined and analyzed wood anatomical characteristics and mechanical properties. The results showed that the average fiber lengths of sapwood and heartwood among five 9-year-old clones ranged from 1099.65 to 1397.61 μm and 962.67 to 1069.21 μm respectively, belonging to the intermediate length category; the average fiber widths of sapwood and heartwood were 21.44-24.46 μm and 21.59-23.69 μm respectively; the fiber length-width ratios of sapwood and heartwood were 46.87-59.17 and 41.67-48.55 respectively. The fiber wall-lumen ratios of sapwood and heartwood in all 5 clones were less than 1, indicating they were top-grade raw materials for papermaking; the average fiber wall thickness of sapwood (4.76 μm) and heartwood (3.38 μm) in ‘Clone 01-24’ was significantly lower than that in other clones. The basic densities of 5 clones ranged from 0.32 to 0.42 g/cm³, all meeting the Grade II standard of basic density for commonly used wood in China. ‘Clone 01-29’ had the lowest air-dry shrinkage rate in sapwood and heartwood, as well as the lowest oven-dry shrinkage rate in sapwood; in 5 clones, ‘Clone 03-27’ and ‘Clone 69’ had significantly higher average compressive strength parallel to grain and bending elastic modulus in sapwood and heartwood than the other three clones, indicating stronger fiber rigidity and toughness. The cellulose content in sapwood and heartwood of ‘Clone 69’ was lower than that of the other 4 clones, while ‘Clone 01-24’ had the highest cellulose content (46.99% in sapwood and 46.27% in heartwood), which was conducive to obtaining higher pulp yield. In conclusion, each of 5 P. deltoides clones exhibits distinct advantages in papermaking performance. Notably, 4 newly selected Populus deltoides clones demonstrate considerable potential as superior clones suitable for pulpwood plantation cultivation.

Key words: Populus deltoides, superior clones, pulpwood, wood anatomy, wood properties