Exploring the Relationship Between Growth Strain and Growth Traits in Eucalyptus cloeziana at Different Age Stages

The harvesting period is determined by forest maturity. However, there are few studies on the continuity of assessing cultivation duration based on both growth and wood quality, especially for Eucalyptus plantations. This study measures growth traits, such as the diameter at breast height (DBH), oblateness, and other characteristics, as well as wood properties like density and crystallinity, and axial surface growth strain levels at four age stages (6, 10, 22, and 34 years) of Eucalyptus cloeziana (E. cloeziana). By analyzing these factors, particularly the changes in growth strain throughout the tree’s development, the study aims to determine the optimal cultivation period for using E. cloeziana as solid wood. The survey revealed a two-stage pattern in the annual change rate of DBH, tree height, and oblateness: a decrease from 6 to 22 years followed by an increase from 22 to 34 years. In E. cloeziana, heartwood percentage and density rapidly declined during the first 6–10 years, then stabilized between 10 and 34 years. This suggested differential rates of growth and maturation. By analyzing the growth strain, it was observed that the growth strain of E. cloeziana exhibited an initial increase followed by a subsequent decrease with age. It reached its peak at 22 years and then gradually declined. Remarkably, at 34 years, the growth strain was even lower than that of 10-year-old E. cloeziana, measuring only 2148 με. This reduction in growth strain is advantageous for minimizing defects such as brittle core formation, cracking, and warping during harvesting. In practical cultivation aimed at solid wood utilization, harvesting can be conducted between 22 and 34 years based on management strategies to reduce operating costs. However, with close-to-nature management practices and sufficient financial resources, extending the cultivation period to 34 years or beyond may result in superior wood quality. We aim to achieve the sustainable utilization of resources, foster the long-term development of the wood processing and solid wood utilization industries, and guide the entire sector towards the goal of sustainable development.