Elasto-mechanical properties and wood quality of bark beetle infested Norway spruce wood

The elasto-mechanical properties and the wood quality of Norway spruce from the regions “Sauerland” and “Harz Mountains”, Germany, were examined after they had been stored standing up to four years after mortality resulting from infestation of bark-breeding beetles. To analyse the impact of standing storage on the elasto-mechanical properties of the spruce, compression strength parallel to the grain, bending strength, bending modulus of elasticity and impact bending strength were determined. Additionally, High-Energy Multiple Impact (HEMI) tests were performed to analyse whether and to what extent embrittlement of the wood occurred depending on its standing storage duration (SSD). No conclusive evidence could be derived that standing storage for up to four years affected the investigated properties over time. The results, rather, suggested that the differences observed are primarily attributed to group-specific differences in density and other properties due to the natural variability of the wood. The wood quality was assessed for log sections based on the General Agreement for Trading Logs in Germany (RVR). The quality decreased with increasing standing storage duration (SSD). Butt log sections showed below-average quality compared to the upper log sections from appendant trees. The main criteria for quality grading were fungal decay and infestation by wood-boring insects.