The overall objective of this project is to maximize the value of Canadian cedars by identifying the strengths and limitations of their natural durability and improve the quality of Canadian cedar products by maintaining and enhancing natural durability.
In Report #1 the fixative agents found to inhibit leaching of western red cedar (WRC) extractives were evaluated for their ability to improve the decay resistance of WRC against a brown rot and a white rot fungus in a soil block test without acting as biocides. Two of the treatments were found to reduce weight loss of WRC by the brown rot fungus Coniophora puteana but did not affect weight loss of ponderosa pine. Fixative efficacy against the white rot fungus, Irpex lacteus, could not be determined because the fungus did not cause significant weight loss in the untreated western red cedar control. Further work is planned to evaluate the field performance of these treatments and to evaluate the performance of coatings on western red cedar treated with these fixatives.
Report #2 describes a new liquid chromatography/mass spectrometry (LC/MS) method for separating extractives from western red cedar. Mass spectral detection provides useful structural information that gives increased confidence in peak identifications and helps to identify unknown peaks. Using LC/MS data, combined with data from UV and NMR spectroscopy, unknown compound J, commonly found in many samples of WRC that we have analysed, was identified as alpha-thujaplicin. This was known to be a major extractive in eastern white cedar but was considered to be a negligible component of WRC. Its potential contribution to the durability of WRC has not been considered in previous work attempting to correlate durability to specific extractives. Continuing LC/MS development will lead to a determination of the abundance of alpha-thujaplicin in the western red cedar resource, new methods for the analysis of heartwood extractives from yellow cypress and eastern white cedar, and further characterization of unknown peaks in western red cedar.
In other work, not included in these reports, initial attempts were made to correlate field test ratings for western red cedar, eastern white cedar and yellow cypress with extractives data. No correlations were evident with four-year data from two test sites, largely because the ratings did not vary much. This will be re-visited after the five-year data from all sites are available and reported at that time.
An experiment was set up to identify fungi capable of detoxifying western red cedar. WRC and ponderosa pine (control) blocks were stored in ground contact for six months and above ground for one year and sampled regularly to measure extractive concentration and to isolate potential detoxifier fungi. Fungal identification is underway and a soil block test against decay fungi is planned to determine whether extractive loss affects decay resistance.