PARENT SESSION
Poster Session #58: Invasive Species Control.
Thursday, August 8. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Control of smooth brome (Bromus inermis Leyss.) through whole-forest restoration in Winnipeg, Canada.

Thompson, Bill^*,1, McLachlan, Stćphane^1,2, ¹ Deptartment of Botany, Winnipeg, MB, Canada² Environmental Science Program, Winnipeg, MB, Canada

ABSTRACT- Less than 5% of the pre-settlement riparian forest exists in Winnipeg, and much of what remains has lower native plant diversity and a greater number of exotics than rural riparian forests. The perennial Eurasian grass, Bromus inermis dominates much of the extant urban forest. It is widely recognized that control of B. inermis is difficult to achieve in grasslands, but little research has been conducted in forests. Our objective was to identify whether the effectiveness of B. inermis control in forests increases when combined with the reintroduction of native species. A replicated long-term experiment was established in 2001 in a highly degraded site, and a neighbouring high quality fragment used as a reference site. Treatments included shade (canopy, artificial, control), disturbance (herbicide, mowing, control), and reintroduction (planting, mulching, control). Shade was negatively associated (p<0.0001) with the density of B. inermis. Application of the grass-specific herbicide sethoxydim and mowing also resulted in the effective control of the exotic, and were most effective in controlling brome density in high shade environments. However, B. inermis regenerated in all treatments, suggesting that additional forms of control are required. Planting of competitive native understory species including Acer negundo, Anemone canadensis and Symphoricarpos occidentalis will increase native diversity in this highly species depauperate site. In addition, increased native vegetation cover should reduce re-emergence of B. inermis in sites that have been disturbed by control treatments. It is anticipated that this restoration based approach to B. inermis control will be necessary in order to increase the long-term integrity of these highly degraded urban riparian forests.

KEY WORDS: urban riparian forest, restoration, Bromus inermis, invasive