Factors Affecting Revegetation of Oil Field Access Roads in Semiarid Grassland

We assessed vegetation recovery on access roads removed after well abandonment in an active oil-producing region of northern Great Plains grasslands. We compared extant vegetation on 58 roads, restored 3-22 years previously, to records of species seeded on each and to adjacent, undisturbed prairie, to evaluate main differences between the restored and adjacent community and to explore patterns in the restored plant community over time. The restored plant community was dominated by low richness of seeded non-native and native grasses and forbs, whereas adjacent prairie had numerous, abundant native graminoids and shrubs and higher richness of native forbs. Cover of seeded species on roads was double that of colonizing species. Disparity in cover of dominant native grasses between the adjacent community and relatively narrow restored roadway suggests that conditions for germination and survival in roadbeds are poor. This is at least partly due to persistence of seeded species. Differences in restored plant composition over time were best explained by changes in species seeded, from non-natives to natives, and secondarily by successional shifts from ruderal to perennial non-seeded species. Of the 30 species seeded at least once on these roads, only 10 were commonly used. The long-term influence of seeding choices in grassland road restorations implies that improvements in these practices will be critical to reversing ecological impacts of roads.