The importance of dispersal in the establishment and proliferation of exotic populations make this life history stage critical in the prediction and management of biological invasions. We observed the dispersal of seeds by patches of smooth brome invading northern fescue prairies and applied an inverse power function model to explore its potential invasion patterns. Based on our observations of two northern fescue prairies in Riding Mountain National Park, Manitoba, Canada, patterns of potential invasion were contingent upon the dispersal of seeds as individual florets or aggregated within spikelets and panicles. For example, although the majority of dispersed seeds were intercepted within one meter, inside and outside the margins of invading patches, slopes of the log–log plots of seed number against their dispersal distance were steeper for seeds dispersed as spikelets than individual florets. Despite the observed aggregation of seeds along the margins of invading patches, the number of dispersed seeds was poorly correlated with that germinated from the seed bank. The shallow dispersal gradient of individual florets and spikelets, combined with the steeper gradient of panicles suggest that smooth brome is capable of simultaneously invading along dense fronts and by establishing isolated foci. Although low correlations between the number of dispersed seeds and their recruitment from the seed bank might suggest postdispersal transport of seeds, other mechanisms, including seed predation and pathogens, remain unexplored. Conservation and restoration of northern fescue prairies must include efforts to control the dispersal of smooth brome seeds and reduce opportunities for their establishment.
Nomenclature: Smooth brome, Bromus inermis Leyss.