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Chaudhry, Ifrah; Pereira, Cassidy; Wallis, Tyler

English holly (Ilex aquifolium), an invasive species in the Pacific Northwest, is known for its rapid spread and ability to disrupt forest ecosystems by outcompeting native vegetation, necessitating immediate intervention. To control English holly in Pacific Spirit Regional Park, UBC students first conducted a 2017 study assessing short-term mortality outcomes following Paint and EZ-Ject glyphosate applications. A follow-up study in 2024 revisited those same sites to evaluate long-term treatment efficacy by measuring holly mortality, quantifying sprout regrowth at various distances from tree bases, and analyzing spatial and ecological variables influencing treatment success. This study, conducted from November 2024 to March 2025 in partnership with Metro Vancouver Regional Parks, followed up in Pacific Spirit Regional Park by examining and comparing two subtypes of EZ-Ject treatments: the “cut” method, where herbicide was applied after removing the upper portion of the tree, and the “uncut” method, where herbicide was injected directly into standing, intact trees. This research aimed to identify the most effective method for controlling holly regrowth by analyzing sprout regrowth, mortality rates, and the distribution of sprouts around treated uncut trees. It was identified that while the uncut method performed better than the cut method in terms of mortality rate (57% and 38%, respectively) and amount of sprout growth (3.47 and 4.77 sprouts per site, respectively), the results were not statistically significant. This was likely due to a small cut site sample size (N = 13) compared to the uncut sample (N = 59). Most sprouting occurred within 0-30 cm of the tree base, with cut trees showing a higher proportion in this zone (58.1% versus 42.3%), suggesting a potentially stronger compensatory response to cutting. Although these patterns were not statistically significant, they highlight how treatment type may influence regrowth dynamics and further support the uncut method as the more efficient option for large-scale management. Since both methods were similarly effective in treating English holly, we recommend the uncut method for future management due to its lower labour requirements and greater ease of application. Spatial analyses highlighted potential confounding variables that may impact future treatment success, such as tree diameter at breast height (DBH) and proximity to standing water. An additional deliverable that came from this research was a map detailing the exact locations of English holly plants in Pacific Spirit Regional Park that require future treatments. This study’s results will provide data-driven recommendations to support Metro Vancouver’s invasive species management strategy, improve resource efficiency, and enhance regional conservation efforts.

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University of British Columbia. ENVR_V 400

Vancouver : University of British Columbia Library

10.14288/1.0448867

Science, Faculty of; Earth, Ocean and Atmospheric Sciences, Department of

Undergraduate

DSpace