Non-destructive measurement of Scots pine heartwood stilbene content and decay resistance by means of UV-excited fluorescence spectroscopy

Decay resistance is an important property of heartwood timber. The decay resistance of Scots pine heartwood correlates with its stilbene content, but the determination of both requires laborious and destructive analyses. To aid in the determination of these important properties, we investigated the feasibility of an optical method based on the intensity of UV-excited fluorescence for the non-destructive measurement of heartwood stilbene content and decay resistance. Fluorescence measurements carried out on samples from 58 trees showed a high correlation (r = 0.79, p < 0.000) between fluorescence intensity and stilbene content. The intensities measured from green and dried samples were highly correlated. The correlation between the fluorescence intensity and mass loss due to the brown rot fungus Coniophora puteana (r = -0.64, p < 0.000) was lower than the correlation between the stilbene content and mass loss (r = -0.78, p < 0.000). Nonetheless, the method showed promise in separating the low and high mass loss samples from the average heartwood material. The fluorescence-based method may be utilized in timber grading and tree breeding, and due to the strong correlation between green and dry measurements, it may be applied at any stage of the processing chain.