York University Tree Inventory: Health

Trees are important parts of urban spaces, and their health is an important concern for urban planners. Urban trees are subject to higher levels of disturbance both directly from human activity or indirectly through pollution or climate effects caused by urbanization. One potential disturbance factor on tree health is ground vibration caused by underground subway lines. Ground vibration from subways has been known to cause structural damage on buildings and structures such as bridges and highways, and trees are analogous permanent natural structures rooted in the ground. To date, there has been little research specifically concerning the effects of ground vibrations on tree health. This study is a longitudinal study examining the effects of a recently built subway line underneath the York University campus on tree health. Using data from a tree census conducted prior to the Toronto Transit Commission subway extension running directly under the university becoming fully functional, and a new set of data collected over October 2020 to March 2021, this study examined the effects of subway disturbance on the growth and health of 745 trees on the York University campus. Trees from ten different species were measured at varying distances from the subway line with groups both within and outside of 200 meters from the subway. It was hypothesized that tree growth and health would decrease closer to the subway, and that species-specific patterns would be observed. However, this study found no significant relationship between distance from the subway and tree growth or health.