The Identification And Characteristics Of Phoebe Zhennan,Phoebe Hui Buried Wood

In this study,the wood microstructural characteristics and wood volatile components were first combined to determine the identification basis of Phoebe zhennan and Phoebe hui buried wood.Then take the samples of known species as research objects which were dated by radiocarbon dating,on this basis,the physicochemical properties of P.zhennan and P.hui buried wood in different years were analyzed and compared with the modern wood.The morphology about pores,wood fibers and parenchyma cells of buried wood and modern wood were compared by optical microscope and electron microscope.The physical and mechanical properties,such as density,shrinkage and expansion,bending resistance and compression resistance,were determined according to the national standards.The color changes of wood and ash were analyzed by chromatic meter.The pyrolysis processes of buried wood and modern wood were observed by thermogravimetric analysis.The change of chemical composition during the formation of buried wood was explained by means of infrared spectrometer,X-ray diffractometer and determination of main chemical composition.The difference of chemical elements between buried wood and modern wood was explained by elemental analysis,the essential oil components were analyzed by GC-MS,and the pH value was determined.This research with a view to systematically and comprehensively analyzing the physicochemical properties of P.zhennan and P.hui buried wood,to explore the influence of burial year on its characteristics.The main conclusions are as follows:The microstructural characteristics of P.zhennan and P.hui buried wood were required to match with the main characteristics of modern wood such as vessel,axial parenchyma and wood ray type.Chemical assisted identification should meet the determination requirements of volatile components in wood.The buried wood must meet the above two requirements of microstructure characteristics and volatile components of wood at the same time,then it can be judged as P.zhennan and P.hui buried wood.All types of cells in buried wood samples were deformed to varying degrees,and the cell walls of the duct,wood fiber,and parenchyma were obviously damaged.The contents of ray cells,ducts,and parenchyma were increased and deepened.For the same tree species,the shrinkage and expansion ratio of buried wood was obviously higher than that of modern wood,the dimensional stability of dark wood was worse than that of modern wood,and the compressive and bending strength of buried wood were lower than that of modern wood.Compared with modern wood,the physical and mechanical properties of dark wood with the longest burial time decreased significantly.The water in buried wood was mainly in the form of free water,and the relative content of bound water was less than that of modern wood.In thermo-gravimetric analysis,the pyrolysis rate of buried wood was lower than modern wood at 300℃,and near infrared spectra of 1738cm^-1 the modern wood decreased compared to the absorption peak of the experimental results and its hemicellulose content presented significant decline in test results.In the infrared spectrogram,the absorption peak near 1738cm^-1 was significantly weaker than that of modern wood.These results were consistent with the test results of significant decrease in hemicellulose content of buried wood.Among the chemical components of buried wood,the hemicellulose degraded in large quantities during its formation,and the longer the buried wood was buried,the more serious the hemicellulose degradation was.The crystalline structure of cellulose was not changed during the formation of buried wood,and the reason why its crystallinity was slightly higher than that of modern wood may be that a small amount of degradation of cellulose in the formation process may occur in the amorphous zone of cellulose.The extraction rate of the essential oil of P.zhennan and P.hui buried wood was slightly higher than that of modern wood,the main components of the essential oil were basically the same as that of modern wood,and the relative content of deta-Cadinene was significantly increased in P.zhennan and P.hui buried wood.There were many good antibacterial compounds in P.zhennan and P.hui wood.The significant decrease of L*value of buried wood is consistent with the observation that the color of buried wood was darker than that of modern wood.Under the joint contribution of L*,a* and b*values,it is speculated that the longer the formation time of buried wood,the more?dark‘its wood color may be.Compared with modern wood ash,the content of metal and Ca elements in buried wood ash was significantly increased,and the enrichment of these elements in buried wood led to the yellow color of buried wood ash.