Variation in the decay resistance and its relationship with other wood characteristics in old Scots pines

The importance of factors contributing to the natural decay resistance of Scots pine wood was studied. The decay rate of sapwood and outer and inner heartwood of 16 ca. 170-year-old Scots pines was first measured. A six-week decay test was performed with 5 x 15 x 30 mm wood blocks in dishes containing a brown-rot fungus (Coniophora puteana). The average mass loss in sapwood was 141 mg/cm³, in outer heartwood 57 and in inner heartwood 108. The variation between trees was largest in outer heartwood. The corresponding basic densities were 439, 456 and 411 mg/cm³. The mass loss was then compared with chemical characteristics and the sorption of water by parallel sample blocks in order to determine which factor has the greatest effect on decay resistance. The differences in heartwood mass loss were explained best by the concentration of pinosylvin and its monomethyl ether, which are phenolics belonging to the group of stilbenes, as well as by the concentration of total phenolics determined by the Folin-Ciocalteu method.