Effects of natural weathering on the chemical composition of cell walls in sapwood and heartwood of Japanese cedar

Exposure to outdoor conditions can cause chemical components on wood surfaces to deteriorate. To develop effective wood protection methods, a deep understanding of the mechanisms of weathering-induced wood surface degradation is required. However, the effects of outdoor exposure on wood at the cellular level have not been investigated in detail. Additionally, a comparative study of the degradation behavior of sapwood and heartwood has also not been conducted. This paper investigated the chemical changes in cell walls in Japanese cedar (Cryptomeria japonica D. Don) sapwood and heartwood during natural weathering using confocal Raman microscopy. Spectral and chemical mapping revealed that heartwood had higher weather durability than sapwood due to the large extractives content in heartwood. Although there were differences in the rates of lignin reduction between sapwood and heartwood, the molecular structures and lignin-degraded sites of the weathered samples were almost identical. The degradation patterns of naturally weathered wood were also similar to that of artificially weathered wood. The knowledge revealed here will help in the development of more effective wood protection methods.