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Rangeland Revegetation Monitoring on Two Pipeline Rights-of-Way in Southern Alberta
Field sites for this study were established in 1987 shortly after the completion of construction of two pipelines in southern Alberta. The Dry Mixed Grass and Mixed Grass Ecoregions (Milo Pipeline Lateral) and the Aspen Parkland, Montane and Fescue Grassland Ecoregions (Porcupine Hills Lateral) were selected for study plots to compare vegetative productivity, plant species composition and animal utilization on the pipeline right-of-way to that of the adjacent native grassland. Field assessments were conducted over four growing seasons.
Grass production decreased, as expected, in the first year after construction, but it then increased, and in the Dry Mixed Grass and Mixed Grass Ecoregions, often exceeded predisturbance levels. Grass production was higher on unseeded than seeded areas. Forb production showed an increase in the first year after the disturbance, and generally remained higher on disturbed treatments than on the control over time. Total herbaceous production showed a general increase with time on all disturbed treatments, particularly at the Milo sites, due to the increase in grass production.
Bare ground was not significantly different between the disturbed areas seeded to native species and the adjacent native grasslands, within four years of construction. For areas seeded to non-native species bare ground was still significantly higher in disturbed areas. After four years litter on areas seeded to native species was greater on the pipeline trench than in the adjacent control area. For all disturbed areas seeded with non-native species, litter was greater than for the controls.
A lack of little club moss on study sites in the Dry Mixed Grass and Mixed Grass Ecoregions resulted in less similarity between disturbed and undisturbed sites over time, especially in areas seeded to non-native species. In the Aspen Parkland, Montane and Fescue Grassland Ecoregions, plant species composition became more similar over time between the pipeline right-of-way and the adjacent control.
Grazing did not show a discernible effect on cover. There were strong, but highly variable trends for higher overall forage utilization on the pipeline trench than in undisturbed control areas at all sites.
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