WOOD RESEARCH Volume 67, Number 2, 2022
YINGZHI CHANG, CHUNLONG ZHENG, XUEJING SHAO, ZHIYI XIA, and Enhua Xi

Seasonal dynamic changes of sapwood and heartwood in larix gmelinii

This study describes the seasonal dynamic changes of heartwood transformation of Larix gmelinii by establishing the relationship between trunk radius, heartwood radius, sapwood width, trunk growth rings and heartwood growth rings in different heights during the growth season with regression analysis. The results showed that the initial age of heartwood formation was 7.25 years. Heartwood began to form when the trunk radius was greater than 2.6 cm, and then the heartwood radius grew 0.85 cm for every 1.00 cm growth of the trunk radius. It was also demonstrated that the significant change and growth rate of heartwood with month were higher than sapwood at the tree base and 1 m height, but lower than sapwood at 5 m and 9 m height. The absolute content of heartwood and sapwood area decreased with tree height, however, the relative content of sapwood area increased with the tree height.

WOOD RESEARCH Volume 62, Number 6, 2017
Enhua Xi and Guangjie Zhao

Visual simulation on accumulation of the differentiating secondary wall layers

This study describes the accumulation of secondary wall layers of the fast-growing Populus×euramericana cv. ‘74 /76’ during the active phase by the methods of polarized light microscopy analysis and computer simulation technology. The results showed that the secondary wall layers of Populus×euramericana cv.‘74/76’ appeared light and shade stratification during the differentiating phase, and the wall layers corresponded to S1, S2 and S3 layer from outside to inside respectively. The S1 and S2 layer of wood fibers were differentiated in May, and the S3 layer was appeared until the July. In addition, the thickness of the three layers all showed a gradual increasing trend. The accumulation process of the secondary wall layers was visually displayed by the computational simulation technology during the active period.

WOOD RESEARCH Volume 63, Number 2, 2018
Enhua Xi

Dynamic relationship between mechanical properties and chemical composition distribution of wood cell walls

Wood is a natural composite material with a complex structure. Its mechanical properties are mainly due to the cell walls. In order to investigate the relationship between mechanical properties and chemical composition of wood cell wall. Nanoindentation and Raman imaging were used to characterize the longitudinal mechanical properties and chemical composition distribution of wood fibers of three years old fast-growing poplar (Populus×euramericana cv. ‘74 /76’) during the growing season at different times. The results were showed that the content and distribution of cellulose and lignin are closely related to the mechanical properties of wood fiber cell walls, especially the cellulose for the longitudinal elastic modulus and the lignin for the hardness of cell walls. It was also demonstrated that the longitudinal elastic modulus and hardness of the secondary wall 2 layer (S2) were strongly correlated to the micro fibril angle (MFA) and crystallinity of cellulose during the active phase.