Fungi are the primary biological agents of wood deterioration and cause major economic losses of wood products globally. Wood in outdoor applications tends to remain wet for extended time periods, making it susceptible to fungal attack. Understanding the factors involved in fungal colonization of wood is important for developing improved methods for preventing decay, but the process is complicated. Several fungal species can occur simultaneously on the substrate, and many of these fungi cannot be isolated by traditional culturing methods. There is the need to use multiple approaches to study fungal communities in exposure conditions that simulate real life scenarios.
Red alder (Alnus rubra Bong.), Douglas-fir (Pseudotsuga menziesii) (Mirb.) Franco) heartwood/sapwood, and western red cedar (Thuja plicata Donn ex D. Don.) field stakes were used to assess fungal colonization in ground contact exposure. Red alder and Douglas-fir sapwood lap-joints were used to assess the incidence of wood-inhabiting fungi in above-ground exposure. Samples were installed at the Starker Post Farm (Corvallis, Oregon, USA), and then collected at various time points over a two-year period. Fungal identification was conducted using culture-based isolation followed by sequencing of the Internal Transcribed Spacer (ITS) region of ribosomal DNA of the isolated fungi, and culture-independent high-throughput Illumina sequencing of the ITS of rDNA.
Community composition of fungi colonizing wood at the site changed with the exposure conditions. Time of sampling, wood types and moisture content appeared to be related to the incidence of molds, white-rot, and soft-rot fungi in lap-joints, whereas location of lap-joint member or joint surface had no effect on fungal community composition. Pirex concentricus and Coniochaeta canina were the most common species in the lap-joint test.
The main factors influencing fungal communities of wood in ground contact were exposure duration, seasonal environmental changes, and wood species. Fungal abundance was higher in the below-ground zone than in above-ground and groundline zones of stakes. White rot fungi tended to dominate over brown rot fungi, and only a few soft-rot fungi were found in the ground-contact exposure test. Ascomycetes were more frequent in the culture-based sequencing method, whereas basidiomycetes dominated in the high-throughput Illumina sequencing. The methodologies extracted very different major fungal taxa at the phylum and genus level with only minimal overlap for the most abundant taxa across the stakes using the two identification methods.
Torres-Andrade, P.A. (2017) Characterization of Fungal Communities in Selected Wood Species by Field Exposure Tests. PhD Dissertation. Department of Wood Science and Engineering. Oregon State University, Corvallis, OR.