Roads function as prime habitats and corridors for invasive plant species, and can contribute significantly to the spread and establishment of weeds inside protected areas. Smooth bedstraw (Galium mollugo) populations have recently expanded in the abandoned agricultural fields of Bic National Park (Quebec, Canada), and may represent a threat to the preservation of plant diversity and to the quality of visitor experience. The main objective of this study was to map the distribution of the species in the park and to delineate factors influencing the abundance of the plant in fallow fields. We hypothesized that road proximity was the main factor explaining the presence and abundance (frequency of recording) of smooth bedstraw in fields. Vegetation surveys were conducted in abandoned agricultural fields, and two logistic regression models were built to examine the relationship between the presence and abundance of smooth bedstraw and environmental and historical variables. Smooth bedstraw populations were also mapped along transportation corridors. The abundance of smooth bedstraw significantly increases within 125 m (410 ft) of a paved road. The recent proliferation of smooth bedstraw in Bic National Park is likely associated with the construction of road embankments during the paving of gravel roads. The paved road network has probably acted as a dispersal corridor for smooth bedstraw, while the abandoned agricultural fields located close to the paved roads provided suitable habitats facilitating population establishment over large areas. We recommended to the park's authorities to cease paving all remaining gravel roads in the park, not only to stop smooth bedstraw invasion, but also the spread of other invasive species of concern.

Nomenclature: Smooth bedstraw, Galium mollugo L.

Management Implications: Roads function as prime habitats and corridors for invasive plant species, and can contribute significantly to the spread and establishment of weeds inside protected areas. We observed this phenomenon in a small national park in eastern Canada, where smooth bedstraw recently invaded abandoned agricultural fields. Plant diversity of these fields is at risk. Abandoned agricultural fields transformed into monotonous white-colored landscapes could also detract from visitor experience. We show in this study that the recent paving of some road sections of the park has probably initiated the invasion. The abundance of smooth bedstraw in abandoned agricultural fields significantly increases within 125 m of a paved road. Controlling smooth bedstraw with herbicides is not an option is this natural park. We recommended ceasing paving all remaining gravel road sections in the park in order to stop not only smooth bedstraw invasion, but also the spread of other invasive species of concern. This presents a challenge, because park authorities face strong pressure from vacationers to pave roads. This study nevertheless provides strong arguments in favour of a nonpaving solution, for the benefit of a more diverse landscape.