Examination of species of wood decay fungi present on hazard street trees in Thunder Bay, Ontario
Abstract
Urban forests are an integral component in modern day urban infrastructure.
Forests systematically planted in unnatural growing conditions are predisposed to injury,
deficiency and disease, therefore requiring regular maintenance. Species of wood
decaying fungi are the most significant threat to the structural integrity of urban trees.
These organisms are capable of colonizing suitable host trees, most commonly through
wounds on the stem, branches or roots of trees in distress. Once established, wood
decaying fungi can enzymatically break down wood components into easily digestible
compounds. Overtime, infected trees can become structurally weakened and hazardous,
resulting in branch breakage and stem failure. In this study, urban street trees were
examined in Thunder Bay, Ontario for the presence of fungal fruiting bodies, with the
purpose of identifying the hazard severity and host specificity among trees colonized by
wood decaying fungi. The tree species, condition, location, size and species of decay
fungi were recorded. A total of 102 infected trees were recorded, with 117 different
occurrences of decay fungi. There were 19 different species of decay fungi identified
and 12 different tree species infected. The three most commonly infected tree species
included silver maple, white birch and Manitoba maple whereas the three most
frequently occurring species of decay fungi were Cerrena unicolor, Pholiota squarrosa
and Pholiota aurivella. The study found that the canopy cover of silver maple in
Thunder Bay will likely decline significantly in the future as a result of an excess of
overly mature trees susceptible to the opportunistic pathogen, Cerrena unicolor. Street
trees only colonized by Pholiota squarrosa are less likely to become a hazard tree as
opposed to trees infected with multiple species of decay fungi. Street trees found with
fruiting bodies of Chondrosterum purpureum likely contain large portions of progressive
sapwood decay and should be viewed as being a high-risk hazard.
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- Undergraduate theses [325]