Relationship between pore structure and gas permeability in poplar (Populus deltoides CL.\u201955/65\u2019) tension wood

Abstract

Key messageThe important anatomical changes in tension wood, e.g., the high fiber ratio and rich mesopores, did not significantly increase the air and nitrogen flow; thus the gas permeability in the longitudinal direction of poplar (Populus deltoidesCL.’55/65′) tension wood is actually affected by the cell tissue macroporous porosity.ContextGas permeability is one of the most important physical properties of wood and is closely related to its internal microstructure, particularly porosity. Tension wood is widespread in woody plants and displays significant structural differences compared with opposite wood.AimsThe study was designed to clarify the relationship between pore structure and gas permeability in poplar tension wood.MethodsThe gas permeability was measured using a self-made device. The meso- and macroporosity characteristics were measured by nitrogen adsorption–desorption and mercury intrusion porosimetry. The flow was simulated using ANSYS Fluent software to illustrate the role of pore structure on permeability.ResultsThe morphological features of vessels have an effect on wood permeability. Compared with tension wood, opposite wood, which has higher vessel ratio, larger cell lumen diameter, and more rich pits, shows stronger gas permeability. Increasing the airflow path will actually reduce the gas permeability. The simulation results are consistent with the experimental results.ConclusionIn hardwoods, the gas permeability in the longitudinal direction is mainly dictated by the vessels. The high fiber ratio and rich mesopore in tension wood do not significantly increase gas flow, suggesting the permeability of wood was actually determined by the cell tissue with macroporous porosity. Vessel tissue ratio, length and diameter, and intervessel pit size were found responsible for influencing the permeability in the longitudinal direction.