Age Variation of Wood Tracheid Morphology of Pinus massoniana Families

The age variation of the Pinus massoniana wood tracheid was studied by analyzing 29 halfsib families of this tree species in primary seed orchard. The results showed that there were significant or extremely significant differences in the 7 indexes including tracheid width, length, length/width ratio, tracheid wall thickness, tracheid wall thickness / lumen ratio, tenderness coefficient, and rigidity coefficient of the tracheid between the early wood and the late wood at the same age. There was no significant difference in the tracheid lumen diameter among the different aged wood, but there were significant difference in the same index between the early wood and late wood. According to the tracheid morphology, it was showed the law that the wood quality of the juvenile trees was superior to that of the middleaged trees, and the early wood was better than the late wood. The evaluation on the pulp making properties by 3 indexes i.e., the length/width ratio, tracheid wall thickness / lumen ratio, and tenderness coefficient indicated that P. massoniana wood was excellent raw material for pulp making and paper manufacture. The fact that there was significant or extremely significant correlation between annual DBH growth rate and tracheid morphology might be taken as the indirect selection index to evaluate the paper making properties of P. massoniana wood. It might be especially suitable for the selection and improvement of P. massoniana families with plenty of genetic test material for paper making property performances. It was proposed that the qualified paper making properties requested greater annual DBH growth rate, smaller tracheid wall thickness / lumen ratio and greater tenderness coefficient. Taking pulp quality and wood production as the preconditions, 15year was determined as the reasonable felling age for P. massoniana families for pulp making plantations.