Wood decay characterization of a naturally infected London plane-tree in urban environment using Py-GC/MS

Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) using a vertical furnace pyrolyzer was applied to the characterization of internal wood degradation in Platanus acerifolia. Wood disks from approximately 92-year-old tree, previously cut down and showing a large infection caused by wood-rotting fungi, were analysed to determine lignin pyrolysis products composition and syringyl/guaiacyl (S/G) ratio. Similar phenolic compounds were found in the sound and extensively degraded wood, as well as in wood samples collected in R-zone, which separate sound and decayed wood. Significant variation of S/G ratio versus wood degradation, instead, was observed. The values showed a decrease of 27.1% from sound to decayed wood revealing a structural fungal degradation of lignin. Furthermore, a less extensive drop (13.7%) of S/G ratio in the R-zone, in comparison with the sound wood, was observed. A principal component analysis (PCA) was performed using the relative peak areas of the 23 identified pyrolysis products. The differentiation between sound and decayed wood was observed in the plot of the two first components as well as the correlation between pyrolysis products was discussed.