Molecular-level community analysis of fungi associated with field-exposed timber stakes

Linda Moss

doi:10.25907/00870

The natural durability of timber contributes to the success of wood in service, with fungal decay is the leading terrestrial cause of wood failure. Timber durability is determined through a combination of field and laboratory testing, which are effective at predicting the service life of different wood species under different climatic conditions. However, these approaches do not identify the organisms responsible for decay and the colonisation patterns of the contributing taxa. Wooden stakes from the Eucalypt species Corymbia maculata (formerly Eucalyptus maculata), Eucalyptus dunnii, Eucalyptus globulus, Eucalyptus globulus-camaldulensis and Eucalyptus nitens, all with varying durability, and Pinus radiata sapwood, were exposed to three sites within ~ 100 m proximity to one another. These microsites consisted of slightly differing environmental conditions; sun-exposed, partially-shaded and shaded. Stakes were collected at four different time intervals, along with the surrounding soils over 18 months for the analysis of the community composition associated with each microsite, wood species and stake zones. Differences between soil and wood-inhabiting fungi were evaluated at 18 months. While fungal succession associated with different wood species, and the microclimatic effects of above ground, ground line and below ground zones of each stake was analysed between four and 18 months. Fungal diversity and community composition were identified using high-throughput sequencing coupled with metabarcoding of the internal transcribed spacer 2 (ITS2) region. The study demonstrated site-driven effects on the community composition of soils, with both sun and shade influencing soil fungal communities. The number of taxa was significantly higher in soil than in wood, and in sun-exposed soil for Ascomycota and Basidiomycota. While, there was a visible effect of microsites on the fungal community composition in wood, this was not significant, but may have become so over time. Coniochaeta spp. and Cladosporium spp., were the most abundant taxa identified in sun-exposed wood, but Pleohelicoon spp. and Berkleasmium spp. were highly represented in the partially-shaded and shaded sites. Basidiomycota had a high abundance of Candolleomyces candolleanus in the sun and shade-exposed wood, and a high abundance of Clathrus archeri in wood at the partially-shaded site. This was very similar to the Basidiomycota taxa in the soil, except Saitozyma podzolica was the most abundant at the shaded site, rather than C. archeri. The Ascomycota taxa Coniochaeta fasiculata and C. gigantospora were abundant in sun-exposed and partially-shaded soils, respectively. Fusarium oxysporum was the most abundant at the shaded site, but was found in all microsites. There was evidence indicating different stakes of the same wood species had different community compositions. Wood species did not appear to influence fungal communities by 18 months. However, the less durable wood species had a high diversity of taxa during early colonisation, which remained relatively high throughout. Some wood species did appear to be more susceptible to certain fungal taxa. For instance, E. dunnii appeared to be more susceptible to Chaetomium spp., while Crepidotus spp. only appeared in E. dunnii during the first six months, and the white rot Ganoderma spp. was only associated with Corymbia maculata. Each stake zone had its own unique community, while sharing a small proportion of taxa. Ascomycota diversity was significantly higher (p < 0.05) above ground by six months, with the most diversity at the ground line upon completion of the field trial. Genera capable of soft rot were predominant throughout. For example, members of Chaetomium spp., Epicoccum spp., Fusarium spp. and Trichoderma spp. had each inhabited different zones at 18 months exposure. Berkleasmium spp. and Anteaglonium spp. were the most common genera. The research demonstrated the effect of site impacts soil fungal communities, and may influence the colonisation patterns of wood-inhabiting fungi after longer exposure times. Wood species appears to have little effect on the succession of fungi, but replicates of the same species have unique taxa, suggesting priority effects from latent colonisation, or inconsistencies in the distribution of wood extractives. Moisture content and oxygen levels have an influence on fungal community composition, this was confirmed by the unique communities associated with the different stake zones.

Molecular-level community analysis of fungi associated with field-exposed timber stakes

Files and links (1)

Abstract

Details

Metrics