Wood Degradation for Wooden Components in Ancient Buildings of Dahui Temple (1513AD), Beijing, China

Summary The Dahui Temple is a traditional wooden Buddhist structure from the Ming Dynasty, situated in Beijing, China. The pillars of the temple were constructed from hard pine ( Pinus , section Sylvestris ). Over centuries of natural weathering, the lignocellulosic polymers of the wooden pillars gradually degraded, causing changes in the microstructure and physicochemical properties of the wooden columns. Microstructural analysis showed the earlywood cells were loosely arranged and distorted, especially in the external sapwood. The latewood cell walls collapsed, losing their original morphology, and exhibited numerous micro-cracks propagating into the cell corners. Compositional analysis indicated a gradual decrease in the principal chemical components from the interior to the exterior due to natural deterioration. The outermost region, being the most severely degraded, exhibited the lowest contents of lignin (16.7%), cellulose (36.2%) and hemicellulose (12.8%). A notable decrease in the intensity of the characteristic FTIR peaks at 1735, 1370 and 1159 cm −1 was observed in the historic timber, implying partial degradation of the polysaccharide fraction, specifically hemicelluloses. Natural degradation resulted in increased relative crystallinity in the exterior regions of the historic timber. Compared to the control timber, the historic timber exhibited elevated equilibrium moisture content (EMC) values across all tested relative humidity conditions (97.3, 75.3, 57.6, 32.8%) at 25°C. Sapwood EMC was higher than heartwood EMC, with the external sapwood demonstrating the lowest dimensional stability. These findings revealed heterogeneous degradation of the historical wooden columns, providing theoretical support for the design of a long-term protective strategy.