Soil and Litter Legacy Effects of Invasive Flowering Rush (Butomus umbellatus) on Lake Erie Wetland Restoration

The Great Lakes region has been impacted by the invasion of over 180 different alien species. As invasives have reduced wetland habitat availability and altered community structure, managers have developed extensive eradication programs. However, even following the removal of dense monocultures, invasive plants can influence native ecosystems through long-term chemical and biological changes, known as legacy effects. My research investigates the potential for these legacy effects following the removal of Flowering Rush (Butomus umbellatus), an understudied emergent in Lake Erie wetlands. This research focuses on how legacy effects of B. umbellatus may influence restoration of native communities and investigates whether the presence of remnant stands of B. umbellatus propagules or litter alters the success of native reestablishment. A seed mix of 25 native species was sown into flats with soil from either native dominated soils, areas with formerly moderate invasions, or areas with persistent Butomus monocultures. These sown plant communities were then subjected to single and combined treatments of living B. umbellatus vegetative propagules and litter alongside unsown flats that examined the response of seedbank communities. The presence of propagules greatly reduced the growth of native seedlings developing in experimental plantings by 69%. While there was no difference in biomass between native seedlings grown in univaded soils and those from areas of B. umbellatus monocultures, native diversity and community evenness were lower. Contrary to initial predictions, B. umbellatus litter increased native biomass and taxon diversity. Planted propagules also reduced applied invasive litter decomposition. Nutrient analysis of soils from sites of monocultures had elevated levels of phosphorus and nitrogen release. This work documents specific negative impacts of this understudied invasive emergent plant on Great Lakes wetland communities. My results demonstrate the importance of controlling vegetative propagules and emphasizes their potential role in inhibiting restoration efforts that are costly and time consuming endeavors for management partners. This work also suggests that there may be possible changes to microbial communities and related ecosystem nutrient cycles once monocultures have developed. My research suggests the presence of legacy effects of B. umbellatus that alter community composition and soil conditions that warrant further investigation.