Lake Cowichan
The Arbutus menziesii, aka Pacific madrone, is named after 19th century physician and Scottish naturalist, Archibald Menzies. The tree’s range hugs along the Pacific Ocean, stretching from the east coast of Vancouver Island down to San Luis Obispo County in California.
Breathing life into diseased Arbutus trees A UBC Forestry master’s student is investigating a probiotic to help this iconic tree weather increased stress from disease and climate change
Grad student Priya Puri
The Arbutus tree is hard to miss. Its orange bark and gnarled, twisting branches stretch out from hillsides towards large bodies of water. Yet, over the past few years, the only broad-leaf evergreen in Canada has been showing signs of distress. Affected by fungal pathogens and other diseases that can cause its leaves to darken and drop, UBC Forestry graduate student Priya Puri (BSc(Forest Sciences)’20) and other researchers in BC and the US, are collecting vital data that could help save this iconic tree. “We hope that this research will fill in some gaps to explain why Arbutus trees are declining,” explains Priya, who is currently in the second year of a Master of Science in Forestry under the supervision of Prof. Richard Hamelin and Prof. Peter Arcese.
19 Branchlines | Fall 2022
Priya – along with Arbutus ARME research group collaborators in BC, Washington and Oregon – are examining whether some varieties of Arbutus fair better outside of their provenances, or where they originated from geographically. Priya’s arm of the project takes place in Lake Cowichan on Vancouver Island and on Texada Island in the Straight of Georgia. She and other BC researchers are examining 44 different Arbutus seed type groups and around 105 subgroups.
“I’m looking at the whole microbiome of Arbutus trees to see which communities of microorganisms – such as different fungi, bacteria and other small, single-celled organisms – might affect tree health”
Samples from Arbutus tree bark, leaves and surrounding soil are sent to a lab for analysis, Priya explains. There, technicians look for causal agents that might make one group or subgroup of tree more vulnerable to the effects of climate change or other environmental factors. In particular, Priya is interested in the trees’ microbiome: the collection of helpful and harmful bacteria, fungi and other microorganisms present in and around them. “I’m looking to see which communities of microorganisms – such as different fungi, bacteria and other small, single-celled organisms – might affect tree health, either negatively or positively, or sometimes both at the same time,” Priya explains. Pathogens that fall into the negative category are part of the pathobiome; whereas, those pathogens that have a positive effect on a tree’s health and longevity form part of their symbiome. While it is yet unclear exactly why Arbutus trees have been on a slow decline throughout their native ranges since the 1970s, climate change is likely at least partly to blame, Priya says.