STUDY ON THE DECAY EXTENT OF WOODEN COMPONENTS OF DANXIA TEMPLE ANCIENT BUILDING BY POLARIZED LIGHT, FLUORESCENCE AND X-RAY DIFFRACTION METHODS

Abstract

In the present study, the decay extent of wooden components from the Halls of Pilu and Tianran ancestor of Danxia Temple ancient buildings was observed by polarized light, fluorescence, and XRD methods. The findings of the investigation can be summarized as follows. Sample No. 1 was identified as red birch wood (Betula albo-sinensis) and sample No. 2 was identified as maple wood (Pterocarya stenoptera). The brightness of crystalline cellulose birefringence in the cell walls of vessels, wood rays and wood fibres, both in decayed red birch wooden components (DRBWC) and in decayed maple wooden components (DMWC), was not obvious, indicating that the cellulose was seriously consumed by fungi. However, the brightness of green fluorescence in the cell walls of both DRBWC and DMWC was very evident, indicating that the lignin was mainly retained or was not consumed by fungi. XRD analysis indicated that wood decay fungi did not change the structure and crystal layer distance of the crystallization zone, but the diffraction intensity decreased to a certain extent. The crystallinity of cellulose was reduced by 11.16%, from 43.29% to 38.46%, in DRBWC and by 52.16%, from 40.68% to 19.46%, in DMWC, demonstrating a reduction in crystalline cellulose. The degradation of cellulose in wooden components will eventually lead to a reduction in their load-bearing capacity. According to the tendency of brown rot fungi of consuming mostly cellulose and hemicelluloses while avoiding lignin, we concluded that both DRBWC and DMWC were seriously degraded by brown rot fungi, in addition to the attack of termites. The low resistance of the two wooden components to fungal decay and termites is the main cause of their deterioration. The results on the extent of decay will provide scientific data for the future conservation and restoration of the Danxia Temple relics.