The presence of landscape disturbances increases the establishment of exotic plants inside natural areas. Here, we examine the effect of human disturbances to prairie landscapes on the distribution and abundance of Kentucky bluegrass and smooth brome, exotic grasses that threaten the integrity of prairie ecosystems throughout the northern Great Plains. Using plant inventory data from Riding Mountain National Park in Manitoba, Canada, we investigated how roads, trails, and the intensity of historic livestock grazing affect the distribution and abundance of exotic grasses. On the basis of our results, both Kentucky bluegrass and smooth brome were more abundant in areas closer to roads. Kentucky bluegrass was also more abundant in areas farther from trails and those historically grazed by cattle. Our research demonstrates that the effect of landscape disturbances on exotic grasses varies between species and suggests that patterns of invasion may reflect different introduction histories. Given our findings, conserving the integrity of northern fescue prairies should account for human disturbances of landscapes and their effects on the proliferation of exotic plants into areas of native prairie.

Nomenclature: Smooth brome, Bromus inermis Leyss. BROIN, Kentucky bluegrass, Poa pratensis L. POAPR.

Management Implications: Our research demonstrates that human disturbance of prairie landscapes, including roads, trails, and historic livestock grazing, affect the distribution and abundance of Kentucky bluegrass and smooth brome in northern fescue prairies. Conservation managers concerned about the proliferation of these invaders throughout the Great Plains can use distances from roads and grazing history to prioritize their inventory and management. For example, by focusing their attention on road margins, managers may be able to reduce the proliferation of Kentucky bluegrass and smooth brome into adjacent areas of native prairie. Our work also illustrates the persistent effect of historic livestock grazing on the abundance of Kentucky bluegrass and suggests that managers could reduce its proliferation by focusing on source areas located within historic grazing disturbances. Future management of northern fescue prairies will require limiting or restoring human disturbances of prairie landscapes in areas where the conservation of native biodiversity is a management priority.