Hot water treatment as a measure to Minimize Growth Stress-Related Defects in the Processing of Falcata (Falcataria Falcata (L.) Greuter & R. Rankin) Wood

Abstract

Falcataria falcata timbers are prone to defects such as heart checks, cracks, and end-splitting when felled, which negatively affect log quality and market price. These defects are caused by growth stresses—mechanical stresses that naturally occur due to cell maturation and the increasing load of the tree crown. While growth stresses cannot be directly measured, they can be assessed through strain measurements. In this study, Surface Released Strain (SRS) was used to assess stress patterns around the tree's circumference, and Residual Released Strain (RRS) was measured to determine residual stress from pith to bark.

The study examined several factors: growth orientation (straight vs. leaning), age (young vs. mature trees), season (dry vs. wet), and geographic location (Regions 10 and 13). Trees with high strain and steep strain patterns were subjected to hot water treatment at 80°C for 48 hours as a thermal relaxation method.

Results revealed that all SRS values were negative, indicating tensile stress near the bark. For RRS, compressive stress was observed near the pith and tensile stress near the bark, with age and channel position (pith to bark) significantly influencing RRS (P < 0.05). boards treated with hot water showed a more balanced strain gradient, with values ranging from 200% to -200% while untreated boards exhibited a steep strain gradient, ranging from approximately 600% to -1,400%. These findings demonstrate that hot water treatment effectively reduces growth stress in F. falcata timbers. Therefore, it is recommended that logs be subjected to hot water treatment before further processing to minimize growth stress-related defects.