Stabilization of hygro-deformation and interaction between earlywood and latewood in Chinese fir

Abstract The alternating arrangement of earlywood (EW) and latewood (LW) in wood growth reflects an optimization structure, where anatomical differences lead to varying properties. This study analyzed the stabilization characteristics of hygro-deformation in Chinese fir, and compared the dimensional responses of intact growth rings and with those of isolated EW and LW during step-wise desorption and adsorption. During both desorption and adsorption, both LW and EW exhibited rapid hygro-deformation initially, followed by stabilization. The stabilization of dimensional changes lagged behind stabilization of moisture content based on evaluating their rates of change. Isolated EW showed significant reductions in hygro-deformation compared to when LW was present, due to the removal of LW’s restraining effect. The radial and tangential shrinking differences in EW before and after isolation were 0.40 and 0.46 %, respectively, as relative humidity decreased from 97 % to 0. The corresponding values were 0.58 and 0.71 % during adsorption (0 → 97 % RH). These results highlight the impact of EW-LW interaction on the hygro-deformation of Chinese fir and are helpful to elucidate the complex nature of wood-water relations.