Establishment of a native bunch grass and an invasive perennial on disturbed land using straw-amended soil.

Native grasslands around the word face increased threats from non-native species. Fescue prairie in North America, in good rangeland condition, is dominated by the perennial bunch grass, Festuca hallii, whereas disturbances are often colonized by Poa pratensis, an introduced perennial rhizomatous grass which is competitive in nitrogen rich soils. F. hallii thrives in typical low nitrogen grassland soils and recovers poorly once disturbed. Disturbance to soil caused by well site construction may decrease organic carbon and potassium, and increase nitrogen, phosphorus, pH and electrical conductivity, creating conditions conducive to invasion by P. pratensis. This research tested the hypothesis that F. hallii would tolerate nitrogen depleted soil, through addition of carbon as a straw amendment to newly reclaimed well sites, better than P. pratensis. Our second hypothesis was that F. hallii is negatively affected by disturbed soil and P. pratensis is not. We treated three sites with three straw amendment rates, seeded monocultures of F. hallii and P. pratensis, and monitored establishment over three years. F. hallii biomass, root biomass, leaf length and cover increased in response to straw treatments, whereas P. pratensis showed little response. F. hallii was positively affected by prior-year soil water, and current-year ammonium and potassium. P. pratensis was positively affected by current-year soil water, potassium and nitrate. P. pratensis responded positively to higher pH and electrical conductivity found in disturbed soil and F. hallii responded poorly. The positive relationship of P. pratensis to pH above 7 could explain why it can invade reclaimed disturbed grassland; whereas the negative reaction of F. hallii might explain its failure to recover. We concluded the addition of straw as a soil amendment is a possible solution to poor establishment of F. hallii.

Restoration of foothills rough fescue grassland following pipeline disturbance in southwestern Alberta.

The effects of pipeline construction and reclamation techniques on the restoration of rough fescue plant communities following pipeline construction in southwestern Alberta, Canada were evaluated after 7-40 years. The pipeline construction right-of-way (ROW) sites varied from no recovery of rough fescue grassland to moderate recovery. The ROW sites had a higher proportion of introduced grasses and forbs, less topsoil, and poorer rangeland health than the adjacent undisturbed grassland. Within the ROW sites, less topsoil was present on those with larger diameter pipe and which had topsoil fully stripped from the ROW during construction. Introduced grasses, Festuca ovina (sheep fescue) and Poa compressa (Canada bluegrass), succeeded in establishment following seeding and persisted for at least 40 years. Poa pratensis (Kentucky bluegrass) dominated many of the ROW sites. Contributing factors to moderate recovery of rough fescue grassland were related to post-growing season pipeline construction, ideally, between August and March, summer or fall seeding, and minimum disturbance trench-only stripping. Reclamation practices appeared more important than time since restoration in the restoration of rough fescue grassland.