Effect of photodegradation on fungal colonization on wood during initial stage of brown-rot decay

Abstract Photodegradation and decay may happen simultaneously on wood under many exposure conditions. The aim of this study was to explore the effect of photodegradation on fungal colonization during initial stage of brown-rot decay of wood. For this purpose, southern pine ( Pinus spp . ) wood was exposed to accelerated UV weathering for different durations, and then decayed by a brown-rot fungus ( Gloeophyllum trabeum ). The changes in wood microstructure, chemical composition, surface color, crystallinity, fungal colonization pathways, and photodegradation products after weathering and decay were evaluated and characterized. The results showed that both weathering and decay led to obvious color change on wood surface. The photodegradation of wood resulted in the formation of cracking in cell wall, thus creating new voids. The photodegradation products, which mainly consisted of phenols, diterpenoid acids, and other lignin derived compounds, appeared in the cell lumen. During the initial stage of brown-rot decay, fungal hyphae invaded into wood through inherent voids such as ray cells, axial tracheids, and pits, and completed the initial colonization after 20 days. After photodegradation, hyphae could also invade wood from the new voids, and the acidic photodegradation products promoted the non-enzymatic degradation process of brown-rot. However, lignin derived compounds seemed to inhibit the further activity of decay fungi.