Removal of an Invasive Woody Plant Species (Fraxinus ornus) from a Garry oak (Quercus garryana) Ecosystem in Victoria, British Columbia

Abstract

Invasive species encroaching on native habits is a significant problem, especially in highly disturbed urban settings. The manna ash, or European flowering ash (Fraxinus ornus), initially brought to Victoria (B.C.) as an ornamental, invaded Summit Hill Park in the 1970s or 1980s. The ash has since established itself in the park, stressing what is Victoria’s largest Garry oak (Quercus garryana) ecosystem. Throughout various one-year methods, removal of the readily coppicing woody plant species. Five trials, each consisting of 40 individuals, were set up. Trials consisted of control, cut-stump, girdle, full-strength glyphosate & half-strength glyphosate cut-stump treatment groups. Tree height, DBH and coppice vigour (shoot height & quantity) were monitored. The data was compared using both one and paired sample t-tests. A basic hydrological, pedological and biological assessment of the site was conducted, including a population analysis of F. ornus. Only the glyphosate-treated groups were successfully killed. The cut-stump and girdle groups coppiced vigorously and the crowns of the girdled ash failed to die off. The thinning of ash trees improved light availability and an increase in reign orchid, licorice fern and Oregon plum were observed in the study site. Non-target effects of glyphosate were absent. Further research is needed to determine which glyphosate treatment worked most efficiently. Moreover, planting native species and oak saplings is recommended to enhance the ecosystem further. In a short-term timeframe, cut-stump glyphosate has been determined as the most effective treatment for killing F. ornus.