A case study of exotic plant invasion into the Rawah Wilderness, Colorado: The role of propagule introduction and survivorship

Only a few studies have addressed the spread of exotic plant species into federally designated U.S. wilderness areas. I sampled for plant species cover and environmental variables along trail transects and along non-trail transects in the Rawah Wilderness and adjacent non-wilderness lands of northern Colorado. I found exotic plant species richness and cover to be higher along trails than far from trails. More exotic plants are established immediately adjacent to the trail edge than 3m or 10m away from trails. I found exotic plant species cover to only slightly decrease with distance from trailhead. I found higher exotic plant cover and richness in non-forested areas and aspen forests as compared to coniferous forest types. Exotic plants are more likely to be found in areas of higher native species richness such as in drainage corridors. This study illustrates that exotic plant species cover and richness is likely to be highest where both introduction of propagules and survivorship are greatest and that traits of these species can be used to predict patterns of invasion. While studying exotic plant invasion into wilderness areas can help build the conceptual framework by which we understand invasions, the exotic plant invasion into this study area is probably not a management concern.