Fungal decay at different moisture levels of selected European-grown wood species

• Modeling fungal decay of wood demands information on minimum thresholds for wood moisture content.
• Moisture requirements for growth and decay of different fungi and wood species were determined.
• Majority of material/fungus combinations required minimum MC for decay below fiber saturation.
• Highest deviations from MC threshold to FSP were found for wood species with low resistance.

Several factors such as local climate, design details, exposure conditions and coatings have an indirect effect on decay in outdoor conditions. Besides all these factors, in particular the wood temperature and moisture content (MC) directly impact on the fungus and its ability to metabolize and degrade wood cell wall substance over time. Therefore the significant role of MC has been addressed in a wide range of field experiments and approaches to establish decay models. However, all these approaches have one crucial aspect in common, i.e. the need for defining a minimum threshold for wood MC that is necessary for the onset of decay and its subsequent progression.The aim of this study was therefore to examine the moisture requirements of different brown and white rot causing basidiomycetes for growth and decay of a wider range of European-grown wood species including moderately durable, durable and even very durable species. Remarkably, the majority of the material/fungus combinations under test it was observed that the minimum MC for fungal decay was more or less distinct below fiber saturation, whereby the highest deviations from MC threshold to FSP were found for beech and Scots pine sapwood, i.e. the wood species with the lowest inherent resistance.