The shrinking and swelling of wood due to moisture changes are intrinsic material properties that control and limit the use of wood in many applications. Herein, hygroscopic deformations of normal and compression wood of Chinese fir (Cunninghamia lanceolata [Lamb.] Hook.) were measured during desorption and absorption processes. The dimensional changes were observed in situ by an environmental scanning electron microscope and analyzed at different hierarchical levels (tissue, cell and cell wall). The relationship between moisture variation and hygroscopic deformation was measured. During initial desorption periods from 95 to 90 or 75% RH, an expansion of the lumen and a shrinkage of the cell wall were observed, revealing a non-uniform and directional deformation of single wood cells. The variation of shrinking or swelling at different hierarchical levels (tissue, cell and cell wall) indicates that the hygroscopic middle lamella plays a role in the deformation at the tissue level. Higher microfibril angles and helical cavities on the cell wall in compression wood correlate with a lower shrinking/swelling ratio. Normal wood showed a more pronounced swelling hysteresis than compression wood, while the sorption hysteresis was almost the same for both wood types. This finding is helpful to elucidate effects of micro- and ultrastructure on sorption. The present findings suggest that the sophisticated system of wood has the abilities to adjust the hygroscopic deformations by fine-tuning its hierarchical structures.

由于水分变化引起的木材收缩和膨胀是控制和限制木材在许多应用中的使用的内在材料特性。这里，杉木 ( Cunninghamia lanceolata)正常和压缩木材的吸湿变形[Lamb.] Hook.) 在解吸和吸收过程中进行测量。通过环境扫描电子显微镜原位观察尺寸变化，并在不同层次（组织、细胞和细胞壁）进行分析。测量了水分变化与吸湿变形之间的关系。在 95 到 90 或 75% RH 的初始解吸期间，观察到管腔膨胀和细胞壁收缩，揭示了单个木材细胞的非均匀和定向变形。不同层次（组织、细胞和细胞壁）的收缩或膨胀的变化表明吸湿性中层在组织水平的变形中起作用。压缩木材中细胞壁上较高的微纤维角和螺旋腔与较低的收缩/膨胀率相关。普通木材比压缩木材表现出更明显的膨胀滞后，而两种木材类型的吸附滞后几乎相同。这一发现有助于阐明微结构和超微结构对吸附的影响。目前的研究结果表明，复杂的木材系统能够通过微调其层次结构来调整吸湿变形。