Sapwood is generally considered as non-durable and assigned to durability class DC 5 according to European standards independent from the wood species. It is commonly agreed that sapwood decays faster than adjacent heartwood, but it is controversially discussed whether sapwood serves as feeder material and thus accelerates onset and progress of decay in more durable heartwood or decays independently from the neighbouring heartwood. Finally, it might even serve as a biological barrier and thus protect adjacent heartwood from decay. Within this study the durability of sapwood and heartwood of Scots pine (Pinus sylvestris), Douglas fir (Pseudotsuga menziesii), and English oak (Quercus robur) were determined in comparison in laboratory decay tests using Coniophora puteana and Trametes versicolor. To examine potential acceleration of heartwood decay in the presence of sapwood specimens with varying sapwood portions were prepared and inoculated for different time intervals. The presence of less durable adjacent sapwood did neither positively nor negatively affect the resistance against fungal attack of Scots pine, Douglas fir, and English oak heartwood under laboratory conditions. Even though the percentage mass loss (%ML) of sapwood increased with reduced sapwood percentages, the %ML and the absolute ML (absML) of all heartwoods remained unaffected after 8, 12, and 16 weeks of incubation. It appears that at least in the presence of well-established fungal mycelium the presence or absence of sapwood does not impact on the fungal resistance of heartwood.

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