Effect of tracheid on water absorption behavior of Cunninghamia lanceolata under freeze-thaw conditions

In this paper, the effects of freeze-thaw cycle (FTC), freezing temperature (FT) and initial moisture content (IMC) on Cunninghamialanceolata’s water absorption behavior were investigated. The porosity was measured with a gas permeability-porosity analyzer, and its tracheid structure changes were obtained using an optical microscope to explore microstructural deformation under varied freeze-thaw conditions. The results showed a maximum increase in water absorption and mean absorption rate of 25.2% and 24.8%, after 30 FTC experiments. The FTC experiments revealed a positive correlation between FTC and both water absorption and mean absorption rate. The FT experiments showed that Cunninghamia lanceolata’s water absorption and mean absorption rate initially increased, then decreased, and increased again with decreasing temperature, due to the tracheid volume change through icing ratio and ice crystal volume alteration. IMC experiments show water absorption and mean absorption rate decrease for cCunninghamia lanceolata with IMC 0-45% and increase for IMC 60-110% post freeze-thaw. The water absorption and mean absorption rate data were fitted to tracheid volume to derive the predictive models. Correlation analysis identifies the strongest impact of IMC on water absorption and mean absorption rate. FTC primarily influenced tracheal volume, while FT had the weakest effect on tracheal volume, water absorption, and mean absorption rate.