The effect of hemicellulose degradation on the mechanical properties of wood during brown rot decay

Incipient decay of wood by brown rot fungi causes measurable strength losses in wood before measurable weight loss occurs. Previous studies have shown that the high levels of strength loss that occur during incipient brown rot decay may be related to loss in hemicellulose. This paper investigates the effect of decay on hemicellulose composition and the relationship to the mechanical properties of the wood. An in vitro test method was used to allow progressive sampling of southern pine exposed to monocultures of a brown rot fungi. The wood was subsequently analysed by mechanical testing and chemical analysis. The results demonstrated a ratio of strength to weight loss of approximately 4:1. The chemical data indicated that early strength loss (up to 40%) was associated with loss of arabinan and galactan components. Subsequent strength loss (above 40%) was associated with the loss of the mannan and xylan components. Significant loss of glucan (representing cellulose) was only detected above 75% MOR loss.