Management experiments on Lake Erie flowering rush

Background/Question/Methods

The Great Lakes region has been impacted by invasion from over 180 different alien species.  While most management strategies have focused on invasive animals, invasive macrophytes have limited habitat availability and altered community structure. Current methods to remove macrophytes include the application of herbicides, pulling, clipping, and inundation. However, the application of a single management method is often inefficient for eradicating most macrophtyes. Flowering Rush (Butomus umbellatus L.) is an invasive currently threatening Northern U.S./Canadian wetlands. The aim of this study was to understand the response of B. umbellatus to simulated management techniques of flooding and clipping in mesocosms. Plants collected from Ottawa National Wildlife Refuge in Oak Harbor, OH were subjected to six combinations of clipping and flooding treatments in 208 L barrels. Nine plants were individually planted in 300 g of natural clay substrate and assigned to one of two depth treatments (3 and 30 cm) and one of three clipping treatments (0, 1, or 2 clippings) to simulate management conditions. From January to April 2013, we recorded light levels, clipping biomass, total leaf number, height, and width to record treatment affect on plant growth. 

Results/Conclusions

Water depth alone did not impact the total leaf area of individual plants throughout the course of the experiment.  Clipping affected leaf area, as once and twice clipped plants had smaller total leaf areas than unclipped plants. Total leaf area of clipped plants was smaller than that of uncut plants, but total leaf area did not differ between once and twice cut plants. A combination of depth and clipping treatments had a significant effect, as the clipped plants in cut and flooded treatments had less leaf area than both groups of control plants. No plants died over the course of this experiment. These results suggest that inundation alone is not an effective management strategy for controlling invasive populations of B. umbellatus; however, combined applications of flooding and clipping may limit the growth of B. umbellatus. Future studies should examine additional cuttings, deeper water depth, and the reproductive responses of B. umbellatus to further limit plant growth and viability.