Distribution and Abundance of Invasive Nonindigenous Plants and Rare Plants at Two Riverine National Parks in the Great Lakes Network

Invasion by non-indigenous plants is widely considered to be a primary threat to species diversity and ecosystem function. Ecosystem changes resulting from these invasions may negatively impact native plant communities as a whole, as well as rare and endangered species. This report explores existing reports on rare plant locations in Mississippi National River and Recreation Area (MISS), and Saint Croix National Scenic Riverway (SACN). No rare plant surveys were performed for this study. In addition, we performed invasive plant surveys on several species considered "target" species of concern at each park. Common buckthorn (Rhamnus cathartica L.) was the most commonly found invasive species. Of the 68 plots sampled in MISS, 53 had at least one invasive species present, and of the 136 plots sampled in SACN, 128 had at least one invasive species present. While this was not an exhaustive attempt to survey all invasive infestations, this study can serve as a template for future surveys and to emphasize the importance of continuity to allow compilation and comparison of data across parks.