Evaluation of xylem maturation manner for solid wood production from Eucalyptus camaldulensis planted in Thailand

The knowledge of xylem maturation manner is importance to foresters and wood processors as it has major implications for end-product quality. This study aims to evaluate the maturation manner of secondary xylem in Eucalyptus camaldulensis for solid wood production. The samples were 45 twelve-year-old trees from 15 families with different radial growth in a progeny test site for the E. camaldulensis second generation in Thailand. Two mixed-effect models (cambial-age dependency and diameter-growth dependency models) were developed for radial variation of wood properties, resulting in that the cambial-age dependency model was a good fitting for all wood properties rather than growth-diameter models, with a few exceptions. Therefore, the secondary xylem of this species matures depending on cambial age rather than diameter growth. Changing ratios of multiple wood properties at 1-year intervals estimated by the cambial-age dependency model became stable after a cambial age of 11.8 years. The wood formed after starting xylem maturation showed 1) longer wood fiber length, 2) smaller number and larger diameter of vessels, 3) larger diameter and thicker wall thickness of wood fiber, and 4) higher density and compressive strength, rather than those formed in the early growth stage. Based on the results, desirable wood properties for solid wood products can be obtained by prolonging the rotation period from the present short rotation periods.