Study On The Structure And Wood Properties Of Phoebe Bournei Thinning Wood

Phoebe bournei is a rare and valuable tree in the Lauraceae family,with beautiful wood figure,fine texture,excellent physical and mechanical properties,and strong aromatic odor.Phoebe bournei is a favorite wood material,however,its natural resources are scarce.In recent years,the artificial afforestation of Phoebe bournei has been carried out in the south of China.Some Phoebe bournei trees were cut to improve the growth rate and wood properties,and thinning wood will be thus produced in this process.Phoebe bournei thinning wood has a high economic value,and research into its wood properties is very essential.Therefore,the macrostructural characteristics,microstructural characteristics,fiber morphological characteristics and its radial variation,physical and mechanical properties,volatile components,and decay resistance of Phoebe bournei thinning wood were studied to provide a comprehensive evaluation of the wood properties,providing a theoretical basis for its application.The main research contents are as follows:(1)The macrostructural structure characteristics were observed under the naked eye,the results show that Phoebe bournei thinning wood is yellowish-brown with a greenish,the wood is uniform in color;The growth ring and ray are evident,while pores and axial parenchyma are not visible to the naked eye.(2)The microstructural structure characteristics were observed by optical microscope and the anatomical feature parameters were measured by software.The results show that Phoebe bournei thinning wood is diffuse-porous,the pores are mainly solitary pores and multiple pores,the clusters are occasionally seen;Pores are small and less,with the density of 19 pores per square millimeter.The proportion of pore is 12.9%and the tangential diameter of the pore is 72 μm;The vessel wall is thin at 5.2μm and the vessel length is medium at 435.2 μm;The axial parenchyma is paratracheal with a proportion of 11.23%;The wood rays are mostly multiseriate,the ray tissue includes homogeneous and heterogeneous rays,and the type of ray tissue is non-storied with the proportion of 10.24%;The end of rays have oil cells,the vesselray pits are scalariform pits and circular pits.There are a lot of starch granules in the ray cells,while no tyloses are seen in the pores,the heartwood of Phoebe bournei thinning wood has not yet formed.The wood fibers are mostly libreform fibers with a fiber proportion of 65.64%.(3)The fibers of Phoebe bournei thinning wood were saperated,and the fiber length,width and lumen were measured under the optical microscope.The fiber wall thickness,length to width ratio,wall to lumen ratio,and lumen to width ratio were then calculated,and their radial variation were analyzed.The results show that length,width,lumen diameter,double wall thickness,length to width ratio,wall to lumen ratio,and lumen to diameter ratio of fiber were 909 μm,25.6 μm,19.7 μm,5.9 μm,36.15,0.30 and 0.77,respectively.The fibers have a thin wall and large lumen with medium fiber length.From the pith to the bark,the fiber length gradually increases,the fiber width variation is relatively constant,the fiber wall thickness and the fiber wall to lumen ratio fluctuating increases,the fiber lumen to diameter ratio fluctuating decrease.(4)The physical and mechanical properties were tested according to thenational standards.The results show that the air-dry density,oven-dry density and basic density of Phoebe bournei thinning wood are 0.480 g/cm3,0.473 g/cm3,and 0.405 g/cm3,respectively,and dry shrinkage and basic density belong to "light".Dry shrinkage,wet swelling,and differential contraction are both small,dimensional stability is excellent.The compressive strength parallel to the grain,bending strength,modulus of elasticity,and impact toughness are 34.91 MPa,83.53 MPa,9.43 GPa,and 62.3 kJ/m2,respectively.The tangential and radial shearing strength is 9.64 MPa and 6.74 MPa,respectively.The end hardness,the radial hardness,and the tangential hardness are 4428 N,2576 N,and 2619 N,respectively.The compressive strength,bending strength,and tangential shearing strength are all belong to class "Ⅲ",the modulus of elasticity,radial shearing strength,and end hardness are belong to class"Ⅱ",while the impact toughness is rated to class "Ⅴ".The comprehensive quality coefficient is wonderful and comprehensive strength is medium,can be used as loadbearing material.(5)The volatile components of Phoebe bournei thinning wood were analyzed by SPME/GC-MS,and evaluation of wood decay resistance by the weight loss of the samples after 12 weeks of decay fungus infestation.The results show that the compounds with a high content in the volatile components of Phoebe bournei thinning wood are terpenoids such as verbenone,which has a certain aroma and can not only be used as a spice but also but also play a role in health care such as antibacterial and anti-inflammatory.The loss weight of the Phoebe bournei thinning wood is 44.1%and the grade of decay resistance belongs to "slightly decay resistance",the terpenoids and sterols in the methanolic extract have some antibacterial action,but they are in small amounts.