Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Geography and Environment

Supervisor

Goldblum, D.

Abstract

Despite the importance of trees to urban ecosystem services and citizens’ well-being, they are an understudied aspect of modern ecology. Although some studies have been conducted in other countries, no urban dendroclimatological work has been conducted in Canada. I investigated the impact of climate on urban tree growth, focusing on Toronto. I collected cores from five tree species: red oak, European linden, sugar maple, Norway maple, and Austrian pine, from street and park locations. I found a difference in environmental stress by location and by species, with street trees exhibiting negative correlations between summer temperature and growth. Norway maple and sugar maple were found to be particularly stressed by summer temperatures, with increases in negative growth-climate correlations in recent years, while red oak and linden were found to be less stressed by climate. An analysis of growth figures found high annual growth rates for both red oak and linden, and low annual growth for Norway maple and Austrian pine. This suggests that certain species may experience decreased growth rates in the coming decades due to climate change. The findings emphasize the need for attention to urban tree management in the face of changing climates, providing insights for urban forestry planning and conservation.

Summary for Lay Audience

This research investigated the impacts of the urban environment and climate on urban trees of the City of Toronto. Five species were sampled: red oak, European linden, sugar maple, Norway maple, and Austrian pine. Tree cores were collected from trees growing in both street and park locations in the city. To answer my research question, I measured the radial growth (tree-rings) of the sampled species and compared the growth to monthly climate variables (temperature and precipitation), as well as by calculating growth rates of the trees. My research found a difference in tree growth by both tree species and growing location (street vs. park), with street trees generally having lower growth rates. I have also found that the two sampled maple species, Norway and sugar maple, are increasingly stressed by high summer temperatures, while red oak and linden had higher overall growth rates and appeared less stressed by temperature. Species’ response to precipitation varied, but linden and red oak were found to be more tolerant of precipitation shifts than other species. Red oak and linden also had high annual growth rates. This research indicates that some species in Toronto’s urban forest may become more stressed in the future.

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