Jen Cleland
Invasive Plants in the Griffy Creek Riparian Corridor
BSES Senior Research 2004

Invasive plants can be introduced to ecosystems in a variety of ways. After introduction, some plants are unable to survive in a new environment, but others thrive. The invasive plants that are introduced to disturbed, open areas with plenty of nutrients and light thrive. Being highly adaptable to specific conditions, like soil moisture and light in disturbed areas or early successional forests, allow the invasive plants to reproduce and spread quickly.

In a new environment, the invasive plants lack predators and enemies, and this gives the plants an advantage over native species, allowing the invasive plants to out-compete the native flora. This threatens the survival of native plant communities, and threatens the native wildlife’s habitat and food sources. Invasive plants disperse throughout an ecosystem using birds, wind, and rivers to transport their seeds and propagules. My study area includes the riparian floodplains surrounding the first and second order sections of Griffy Creek, immediately above Griffy Lake, as well as the outflow of University Lake – a first order tributary of Griffy Creek. The stream collects run off from residential areas and the Indiana University Golf Course, which could be a source of invasive plant seeds and propagules. The stream is also an agent of dispersal and creates habitat for invasive plants. The riparian area also acts as a dispersal agent to invasive plants. The banks along the creek provide the invasive plants with a disturbed habitat with plenty of light, and can promote the spread of seeds and propagules.

The riparian floodplains in my study area were Platanus occidentalis and Juglans nigra. The understory of the floodplain forest was often open, but in some sites, the understory was thick with invasive species. I assessed the presence of the invasive plants in the floodplains of the Griffy Preserve and near by areas. Floodplains were classified by width. Small floodplains were up to 75 meters wide, medium floodplains were 76 – 150 meters wide, and large floodplains were 151 meters and wider. Locations for transects will be selected randomly for those categories occurring frequently throughout the study area. However, categories that only occur once or twice throughout the study area will not be randomly chosen. They will be specifically chosen to ensure each category is included in the study.

I laid 30 meter transects parallel to the creek across the floodplain, at the base of the uplands, and 5 meters beyond the base of the upland. At each meter along the transect I recorded the presence of invasive plant species. Invasive plants were considered present if they were found rooted in the plot, or hanging over the plot. The invasive plants found in the floodplains included Alliaria petiolata, Berberis thunbergii, Ligustrum vulgare, Lonecera japonica, Lysimachia nummularia, and Rosa multiflora. The most abundant invasive plants in the transects were L. vulgare, L. japonica, and R. multiflora. Plots containing invasive plants will be compared to those lacking invasive plants. The presence of invasive plants within each floodplain category will be compared to the other two categories.