Regulation of Lake Ontario water levels since the 1960s has been associated with an increase in cover of hybrid cattail (Typha x glauca) in the lake’s coastal wetlands. These wetlands have been negatively impacted by the growth of this clonal dominant as it has displaced native graminoids in the biodiverse wet meadow zone. To address this issue around Lake Ontario, previous efforts to restore the wet meadow zone have focused on managing cattail and updating the lake regulation plan. However, the effects of these methods on invasive species such as reed canary grass (Phalaris arundinacea), and abundant native grasses such as Canada bluejoint (Calamagrostis canadensis) have not been fully studied. In 2023, we conducted vegetation sampling in eight wetlands around southern and eastern Lake Ontario and the Upper St. Lawrence River to determine how previous cattail management has impacted the wet meadow zone following recent changes to the water regulation plan. Four of these wetlands have had chemical and mechanical cattail treatments implemented at the wet meadow – cattail interface between 2010-2018, while the remaining four wetlands have not been treated. Wetland sites were paired based on hydrogeomorphic type and wetland size. Results from 2023 suggest that restored sites had lower percent cover of Typha at higher elevations, but greater cover at lower elevations compared to unrestored sites. Calamagrostis cover was more prevalent in the middle elevations in the restored sites compared to the unrestored sites, while Phalaris trends varied greatly by site. The 2024 survey results will be added to examine changes over time. Results of this research should be considered by restoration practitioners when restoring wet meadow habitats and planning for potential impacts to non-target species and overall ecosystem functioning.
