The Variability Of Micromechanics Properties Of Tracheids Of Larix Olgensi Plantation

Softwoods are usually treat as the model material for theirs simple microstructure. Single fiber tensile and nanoindentor were used to investigate the mechanical of cell wall. The variation in a tree and clones of the mechanical property of Larix wood tracheids were researched. The variation was studied of single tracheids of Larix from the point of view of biomechanics. The research of mechanical behavior of multi-tracheids not only perfects mechanical research, but also can explain the complex behavior of tracheids of Larix olgensi.The main research results were summarized as following:(1) The modulus of elasticity, tensile strength and breaking elongation of single tracheids of later wood were significantly greater than early wood of Larix olgensi (at0.01level). The modulus of elasticity, tensile strength and breaking elongation of single tracheids showed significant differences among different growth rings with a single tree (at0.01level). The modulus of elasticity and tensile strength of single tracheids showed significant differences among different height of a single tree (at0.01level), whereas the breaking elongation showed insignificant difference.(2) The results revealed that the modulus of elasticity, tensile strength and breaking elongation of single tracheids of different clones were11.44Gpa,616.59MPa and6.54%, respectively, with the corresponding variation coefficient being26.97%,26.26%and23.17%. The modulus of elasticity and breaking elongation of single tracheids were significantly different (at0.01level) among different clones of Japanese larix, whereas the tensile strength showed insignificant difference. The modulus of elasticity, tensile strength and breaking elongation of single tracheids showed significant differences among different growth rings with a single tree. The repeatability of the modulus of elasticity and breaking elongation of Japanese larix clone were0.79and0.57, respectively, indicating this two mechanical property indexes of tracheids being under moderate to strong genetic control. These results indicate that there are great potentials for early clone selection and genetic improvement in wood properties of Japanese larix clones.(3) In situ imaging nanoindentation was used to characterize the differences in longitudinal modulus of elasticity and hardness of different cell wall layers of Larix olgensi later wood tracheids, the results revealed that the modulus of elasticity and hardness of S2layer of Larix olgensi tracheids were16.32GPa、391.55MPa, respectively, with the corresponding of compound middle lamella being8.47GPa、285.90MPa. the modulus of elasticity and hardness of S2layer of Larix olgensi tracheids were decrease with the increase of the trees, and the range of the hardness reduce less than elastic of modulus. Mature wood’S2layer of elastic modulus is greater than juvenile wood of10.8%and the hardness is greater than juvenile wood of9%. The modulus of elasticity of different cell wall layers of larix olgensi later wood tracheids have positive linear relationship with hardness.(4) Hardness of single tracheids were significantly different (at0.051evel) among different clones of Japanese larix, whereas the modulus of elasticity showed insignificant difference. The research indicated that Hardness of tracheids is strong genetic control. These results indicate that there are great potentials for genetic improvement in wood properties of Japanese larix clones.