Influence of xylem growth ring width and wood density on durability of oak heartwood

Oak (Quercus sp.) is considered as one of the most durable European wood species. The most important factor influencing oak durability is extractive content. In our work, we were interested in the effect of ring width and related density on oak-wood durability. Therefore, oak heartwood specimens made of boards with different ring widths were exposed to five different fungal species Daedalea quercina, Antrodia vaillantii, Hypoxylon fragiforme, Stereum hirsutum and Trametes versicolor according to the EN 113 Procedure. In parallel, extractives and nitrogen content were determined as well. From gravimetrically determined mass losses and a microscopical analysis of decayed specimens it can be resolved that oak heartwood specimens with the narrowest growth rings and consequently lower density are more susceptible to fungal decay than denser specimens made of wider growth rings. Durability of oak heartwood with rings of 0.77 mm and density around 550 kg/m3 is comparable to durability of common beech.