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Investigating Street Tree Decline and Mortality in Commercial Urban Spaces Revitalized with Structural Soil Cell Technology to Improve Planting and Maintenance
Camilo Ordóñez Barona, PhD
Toronto Metropolitan University
(previously Ryerson University)
Growing trees in highly urbanized areas, such as downtown commercial districts, can be extremely challenging. Engineered subsurface systems, such as structural soil cells, can improve growing conditions, but few studies examine how trees perform in these systems in real-world settings. Understanding these dynamics can help improve urban forestry practices.
Between 2015 and 2017, we investigated street tree decline and mortality in two Toronto, Canada, revitalization projects with London planetrees (Platanus X acerifolia). At Bloor Street, initiated in 2010 and planted with 133 trees, most trees declined after five years and all were replaced in 2015 with new species. At Queens Quay boulevard, initiated in 2009 and planted with 154 trees, most trees largely survived and continue to grow there. Data collected included tree growth and health, dendrochronology, soil chemistry and moisture, and other environmental conditions.
We found that de-icing salts had a role in elevating soil salinity and alkalinity, which were, in turn, associated with reduced tree foliage, structural condition, and mortality. Trees exposed to lower salt levels in the soil tended to survive longer and grow better. Yet, tree growth and health was also influenced by the combined effects of soil chemistry, sunlight availability, and physical damage, emphasizing that tree decline rarely results from a single factor.
Careful streetscape design and management practices – such as modifying soil systems, monitoring soil chemistry, improving irrigation, and raising awareness about road salts – can reduce stress and improve tree performance. Monitoring ecological, environmental, and social conditions alongside tree performance can allow cities to evaluate the successes and limitations of revitalization projects and ensure that urban trees survive and contribute to climate resilience and sustainability goals.
This research study was funded in-part by TREE Fund's 2016 Jack Kimmel International Grant Program. You can see more information in these peer-reviewed articles:
https://doi.org/10.1016/j.envpol.2017.11.101
https://doi.org/10.48044/jauf.2018.011
https://digitalcommons.lmu.edu/cate/vol12/iss1/1
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