Recovery of mixed grass prairie on restored oil access roads

Throughout the Great Plains of North America, access roads constructed by the petroleum industry on public lands are removed when no longer needed.  This process involves reshaping the roadbed and planting a seed mix, with goals that include the restoration of the native plant community.  The objective of my research was to evaluate the long-term outcome of these restoration efforts within the plant community.  I studied 58 roads in the Little Missouri National Grasslands, USA, restored from 3 to 22 years previously.  I sampled vegetation within the restored area of each road and compared it to both adjacent prairie and seeding records from the restoration.  I explored how vegetation patterns related to environmental characteristics, landform, and the age of each site.  Vegetation patterns were most strongly related to differences between the restored road and adjacent prairie, even on the oldest roads.  The roadbed was dominated by a low diversity of seeded species, primarily non-native and native grass and forb cultivars, whereas adjacent prairie was composed of a greater diversity and higher proportions of native graminoids, forbs and shrubs.  Colonizers from surrounding prairie were mostly weedy or early successional species.  There was evidence for the colonization of some dominant perennial grasses, though the large disparity in their cover on and off roads and the minimal colonization of many other species common in the surrounding area suggest conditions for survival in the roadbed are poor.  Facilitating a quicker return to a native community may require improvements in both soil preparation and seed selection.