Genera Identification And Structural Changes In The Cell Wall Of Wood From Ancient Timber Architecture And Waterlogged Archaeological Relics

This study of radiocarbon dating,wood identification and cell wall structure changes mechanisms of wood from ancient timber architecture and waterlogged archaeological relics is devoted to clarifying the information about ancient cultural,providing the theoretical basis and data for strengthening and conservation.Studies were carried out on forty-one decayed wood samples extracted from the twelve ancient timber structures representing the wood heritage overground.Meanwhile,the seventy-nine waterlogged archaeological wood samples extracted from three different sites in Liangzhu city representing the wood heritage underground.According to the radiocarbon dating and genera identification technology,the principles of timber used in each ancient timber structures or sites were present.Moreover,the differences of wood cell wall structure and chemical constituents between archaeological wood and reference material were explored and analyzed to reveal the relations among the state of preservation and preservation environment,sampling position,wood genera.The main results of this study are summarized as follows:ⅠAncient cultural information of wood from ancient timber architecture and waterlogged archaeological relics(1)The radiocarbon dating of samples taken from twelve structures not only supported the reference value of the historical records,but also supplemented information about the maintenance data.From this study,eleven genera were identified according to wood anatomy.The timber used in ancient wooden structures was probably taken mainly from local forest resources.This causes diverse levels of consistency in the materials used for different regions.Furthermore,ancient carpenters in Shanxi Province understood the properties of the various local timbers and made full use of durable substances through a systematic reuse of the timbers.(2)Seventeen timber-tree genera that were identified showed the timber of Liangzhu city in Neolithic period also uses local materials within a narrow range around the sites restricted by gathering and hunting.Meanwhile,the timber used in the three sites was less affected by wood property of various timbers since the irregular genera in different artifacts.The characteristics of timber used also could be affected by the position and functions in each site.ⅡStructural changes in the cell wall of wood from ancient timber architecture and waterlogged archaeological relics(1)The differences of anatomical structure and chemical constituents between decayed wood and reference material were studied.In the decayed process,the hemicellulose is firstly degraded in the cell walls of sapwood.The relative content of carbohydrates is reduced since the unstable cellulose.The concentration of lignin is stronger in cell walls.Meanwhile,the S2 layer in secondary cells wall of latewood is the main fungal attacks regions in the decayed wood.(2)The residual secondary cell walls of waterlogged wood are porous and contain minute holes.The preferential decay of polysaccharides shows in the degraded cell walls.The crystalline cellulose was also degraded.The acetyl group in hemicelluloses is completely loss.Meanwhile,the lignin contribution in cell walls was much stronger than in the reference,but the chemical composition did not change.Moreover,the concentrations of C,O,Fe and Si were various in the waterlogged wood.(3)Our investigations show that even a small difference in heights,it can also play an important role for the preservation of decayed wood from the ancient timber structures.It indicated the more close to the bottom of the decaying wood,the deeper the degree of degradation.(4)Variations between preservation environments create difficulties in state of preservation of waterlogged wood.The degree of samples in Meirendi site was greater than the Bianjiashan site.The samples in Mojiaoshan site is the best preserved wood in these three sites.However,there is no general relation between age and decay rate.(5)The state of preservation is affected by the sampling position.The distribution of the decay showed higher fungal and bacterial attacks on the external layer and topside of the poles,while the inner portions or the bottom were less attacked.(6)The wood genera is also an important factor in the fungal and bacterial decay waterlogged archaeological poles.Even small variations of preservation environments differences,have an effect on hardwood(Castanopsis)in waterlogged environments.