A canker disease caused by the fungus Quambalaria coyrecup is devastating Corymbia calophylla trees throughout much of its native range in the southwest of Western Australia. Disease incidence is higher in remnant stands bordering cleared land such as road edges where there is greater anthropogenic disturbance. It is likely that a combination of factors is predisposing C. calophylla to canker disease: climate change, fragmentation, introduction of pathogens, leaching of fertilizers from agricultural land and changes in microclimate as a result of disturbance. These factors can have detrimental effects on concentrations of nutrients in the soil, soil composition, and communities of mycorrhizal fungi. This project examined these potential predisposing factors and how they may interact with C. calophylla along a disturbance gradient. Seventeen sites were selected. Each site consisted of a disturbance gradient of three transects: remnant stand bordering cleared land and a road, a forest edge, and the middle of intact forest. Soil was collected from ten trees along each transect and the nutrient composition was tested. This soil was used in a glasshouse experiment from which roots were harvested to test mycorrhizal composition. Results demonstrated differences in soil nutrition between the disturbed and intact forest transects. The mycorrhizal communities differed significantly among the three transects with the community along the disturbed edge having a unique community assemblage. Concentrations of soil macro- and micro-nutrients were correlated with changes in mycorrhizal communities and canker incidence along disturbed edges, as were C. calophylla stem basal area and overstory tree diversity. Soil moisture, pH and mycorrhizal species richness were also correlated with canker incidence. It is possible that the microclimate along disturbed edges is disrupting communities of mycorrhizal fungi which is altering nutrient acquisition by the trees. The combination of decreased mycorrhizal fungal richness and changes in microclimate along disturbed edges could be responsible for predisposing C. calophylla to canker disease
