Analysis on Wood Properties of Four 12-Year-Old Fast-Growing Ulmus pumila L. Clones in Hebei Region

Objective To investigate the differences in growth and wood property indices among Ulmus pumila L. clones, analyze the wood properties of fast-growing U. pumila clones, and provide a theoretical basis for germplasm innovation and wood processing and utilization.

Method Three fast-growing U. pumila clones (No. 11, No. 12 (Hebei-approved improved variety ‘Jiyu 4’), and No. 13) and one relatively fast-growing clone (No. 17, nationally recognized new variety ‘Sunny Girl’) from the comparative experimental forest of U. pumila clones in Cangzhou, Hebei Province were used as materials. Five growth indices (tree height, DBH, basal diameter, volume, and crown width) and 22 wood property indices (including wood density, shrinkage, swelling, bending strength, compressive strength, comprehensive strength, etc.) were measured at 12 years old. The differences in each index among clones and their correlations were systematically analyzed.

Result The growth indices (tree height, DBH, basal diameter, and volume) of clone No. 17 were significantly lower than those of the other three clones (P < 0.05). There were significant differences (P<0.05) in 22 wood physical and mechanical indices among clones. Most pairwise growth indices were significantly positively correlated, and a similar trend was observed among wood property indices (P<0.05); in contrast, most growth indices were significantly negatively correlated with wood property indices (P<0.05). Clone No. 17 had the highest wood density, followed by No. 12, while No. 11 and No. 13 were relatively lower. Clone No. 13 had the best dimensional stability (shrinkage rate, swelling rate, and differential shrinkage value). Clone No. 17 showed the best mechanical properties (bending strength, compressive strength, and hardness), followed by No. 12, while No. 11 and No. 13 were relatively weaker. Principal component analysis of wood property indices showed that the cumulative contribution rate of the first three principal components reached 85.55%. The comprehensive evaluation ranking via membership function method was No. 17 > No. 13 > No. 12 > No. 11.

Conclusion Clones No. 12 and No. 17 can be used in scenarios requiring high strength and wear resistance. Clones No. 11 and No. 13 are more suitable for occasions demanding light weight, heat insulation, and easy processing. Clone No. 13 is less prone to warping and cracking under varying humidity environments, thus applicable to the production of spliced flooring, wooden door and window frames, furniture panels, etc.