Microscopy evaluation of microbial decay patterns in wood stakes after 6 years in soil contact
IRG/WP 10-10715
A Pilgård, C G Björdal
Most studies on wood modification have so far been concerned with service life predictions rather than investigating the decay protection mechanism. Very little is known about the mode of action of these new treatments and about the strategies used by wood degraders in order to utilize the wood material despite a treatment. Access to such knowledge would allow further modification and improvement of durability of these products. The aim of the present study was to investigate the variation in microbial degradation of wood samples exposed in soil, in an EN 252 field, test for six years. Light microscopy was used for assessing degree and type of decay. Wood stakes of furfurylated and copper organic treated P. sylvestris heartwood were compared to untreated stakes of P. sylvestris. Samples for analyses were taken from three different parts of each stakes; below ground level; soil surface region, and above ground level. In general, the degradation and decay by microorganisms was greatest in the soil surface area. Brown rot, white rot, soft rot and tunnelling bacteria were found degrading the wood. Variations in decay were observed between furfurylated wood and copper organic treated wood. White rot decay were most common in furfurylated wood, where as brown rot were only present in copper organic treated wood. Soft rot was found active in a majority of the stakes. Furfurylated stakes treated to a medium treatment level were more resistant to soft rot decay than furfurylated stakes treated to a low treatment level.