Plant species diversity of highway roadsides in southern New England

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Mowed roadsides represent a significant proportion of the grassland habitat in New England, but they receive little attention from naturalists. We sought to test the assumption that mowed roadsides are ecological wastelands dominated by deliberately seeded introduced perennial grass species. Surveys of seven sites in Rhode Island during the summer of 2008 revealed that roadsides are important refugia for grassland plants, including two species and two subspecies believed to be rare in New England. We found 80 grass and forb species, 45% of which are native. We also examined the effects of distance from the road and topography on the relative distributions of annual versus perennial species and of native versus introduced species. Perennial species cover increased with distance from the road at all seven sites, and the number of perennial species increased at five sites. The front slope had the most annual species and the most annual cover at all sites. Perennial species dominated the back slope, swale, and flat areas. Neither distance from the road nor topography had a clear effect on the distribution of native species relative to introduced species. Highway roadsides in southern New England are not an ecological wasteland, but rather are a complex upland grassland habitat reminiscent of the agricultural grasslands which dominated the region in the nineteenth century.

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Northeastern Naturalist