Finnish Forest Research Institute  Metla

Press release 18.08.2006

Better methods for measuring decay resistance of timber

The heartwood of Scots pine (Pinus sylvestris L.) is the source of naturally decay-resistant timber. However, utilizing heartwood timber is hindered by the wide variation in the decay resistance. The variation is primarily due to variation in the concentration of heartwood extractives in trees. The higher the concentration of phenolic compounds in heartwood, the better it can resist wood-destroying fungi. Measuring total phenolics with the Folin-Ciocalteu (FC) assay can be used as a tool when developing quick characterization methods for timber to meet the needs of industry. The results were obtained in a study conducted by the Finnish Forest Research Institute (Metla).

A research group in Metla’s Punkaharju Research Unit is performing research to determine factors that affect decay resistance in heartwood timber and to seek possibilities to exploit natural decay resistance and to reduce variation of durability.

There is wide variation in natural decay resistance among individual trees. To be able to exploit the most decay-resistant heartwood, methods are needed to screen for decay resistance from large amounts of timber. However, there are several reasons why screening timber cannot be performed through actual decay tests. At the scale of the sawmill industry, screening would necessitate rapid, non-destructive tests. Since the decay tests are too slow, interim means must be applied to enhance development of sufficiently rapid methods for practical implementation.

The results of this Metla study indicate there is a strong correlation between the decay resistance of Scots pine heartwood and the concentration of the extractives. A high concentration of phenolics in heartwood improved its durability against the brown-rot fungus (cellar fungus, Coniophora puteana). Furthermore, measuring the concentration of total phenolics was much quicker and easier than performing decay tests. Thus, the FC assay based on measuring the total phenolics concentration could complement or even replace the in vitro decay tests when new methods are being developed for screening and characterizing decay-resistant timber apart from lower-quality timber.

Publication: Anni M. Harju & Martti Venäläinen. 2006. Measuring the decay resistance of Scots pine heartwood indirectly by the Folin–Ciocalteu assay. Canadian Journal of Forest Research 36(7): 1797–1804.

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