Disturbance frequently is implicated in the spread of invasive exotic plants. Disturbances may be broadly categorized as endogenous (e.g., digging by fossorial animals) or exogenous (e.g., construction and maintenance of roads and trails), just as weedy species may be native or exotic in origin. The objective of this study was to characterize and compare exotic and native weedy plant occurrence in and near three classes of disturbance -digging by prairie dogs (an endogenous disturbance to which native plants have had the opportunity to adapt), paved or gravel roads (an exogenous disturbance without natural precedent), and constructed trails (an exogenous disturbance with a natural precedent in trails created by movement of large mammals) - in three geographically separate national park units. I used plant survey data from the North and South Units of Theodore Roosevelt National Park and Wind Cave National Park in the northern mixed-grass prairie of western North and South Dakota, USA, to characterize the distribution of weedy native and exotic plants with respect to the three disturbance classes as well as areas adjacent to them. There were differences both in the susceptibility of the disturbance classes to invasion and in the distributions of native weeds and exotic species among the disturbance classes. Both exotic and native weedy species richness were greatest in prairie dog towns and community composition there differed most from undisturbed areas. Exotic species were more likely to thrive near roadways, where native weedy species were infrequently encountered. Exotic species were more likely to have spread beyond the disturbed areas into native prairie than were weedy native species. The response of individual exotic plant species to the three types of disturbance was less consistent than that of native weedy species across the three park units.
Bibliographical noteFunding Information:
plied by S. Marks, A. Beaulieu and M. Dinkins, with special thanks to P. Anderson for training and supervision. Theodore Roosevelt and Wind Cave National Park staff, especially P. Andersen, B. Muenchau, M. Curtin, R. Runge and D. Roddy, provided logistical support and background information on the parks. S. Ogle provided the digitized terrain map for WCNP. The TRNP vegetation coverage was developed and ground-truthed by J. Norland and edited by S. Hager. D. Buhl provided statistical advice and J. Fahnestock, R. Gleason, Q. Guo and two anonymous reviewers commented on earlier drafts of the manuscript and significantly improved it. Support for this study was provided by USGS through the Natural Resources Protection Program and Northern Prairie Wildlife Research Center.
- Great plains
- Invasive plants
- Natural areas
- Prairie dogs