PARENT SESSION
Oral Session #63: Invasive Species: Terrestrial.
Presiding: D. Larson
Wednesday, August 7. 1:00 PM to 4:45 PM. Graham Meeting Room, TCC.

Exotic plants and propagules on roadsides and adjacent shortgrass steppe.

Lauenroth, William^*,1, Betz, DaniElla², ¹ Department of Rangeland Ecosystem Science, Fort Collins, CO² Graduate Degree Program in Ecology, Fort Collins, CO

ABSTRACT- Some grassland plant communities have undergone significant changes due to exotic invasive species, while others have been unaffected. The shortgrass steppe is an example of a grassland that has been relatively unaffected because it has had few established exotic species. Roadsides are known to provide favorable conditions for exotic species and they may act as corridors, facilitating the movement of invasive species into the adjacent undisturbed vegetation. We conducted a vegetation survey of roadsides and adjacent steppe as well as a seed bank study of the western section of the Pawnee National Grassland in an attempt to understand if roadsides were an important potential source of exotics for adjacent steppe and the degree to which propagules were disseminating from the roadsides into the steppe. We found that roadsides contain high species richness and canopy cover of exotic plants. A total of 26 exotic plant species occurred in roadsides compared to 6 in the adjacent steppe. Relative cover of exotics averaged 40% on roadsides and less than 1% in the steppe. Roadside seedbanks contain high species richness and large numbers of seeds of exotic species suggesting large propagule production. Despite this, relatively few seeds of a small number of species are being dispersed into the adjacent steppe.

KEY WORDS: exotic plants, roadsides, seedbank