Resistance to fungal degradation of modified and unmodified wood

Sammanfattning

The inherent resistance to fungal degradation of wood was studied using the paste test method. Samples of three different types of wood, Norway spruce (Picea abies), Scots pine (Pinus sylvestris) and European beech (Fagus sylvatica), were initially ground to a powder followed by being inoculated with two types of rot fungi, brown rot fungus (Rhodonia placenta) and white rot fungus (Trametes versicolor). To analyse how different modification methods may affect this resistance, acetylated Norway spruce and thermally modified Scots pine and European beech was inoculated as well. The influence of the degradation products formed during the thermal modification process was studied by solvent extraction on parts of the thermally modified samples. The growth was followed over time by taking pictures and analyse the area covered by the fungus by image analysis. Statistical analyses of fungal growth on petri dishes mixed with untreated samples indicated no significant difference in the growth per day. However, a difference in the maximum growth rate was shown where F. sylvatica exhibited a higher growth rate than the other two species. For the modified samples, several significant differences were observed both internally between modification methods within the same wood species and externally in the combination of different wood species and different modification methods. Samples of F. sylvatica that were both heat-treated and where the degradation products were extracted had a lower resistance to fungal attack than samples of other wood species and or modification treatment.