Led By: Danielle Bilyeu Johnston
Study Area: Piceance Basin
Project Status: Ongoing
To develop reclamation techniques for big sagebrush habitats impacted by oil and gas development in northwestern Colorado.
To test various weed control techniques.
To promote a diverse set of native perennial plants.
To preserve wildlife habitat in oil and gas fields, wildlife managers have to restore impacted areas. This involves preventing soil loss, controlling weeds, and promoting the growth of native plants. Oil and gas fields create many small areas of disturbances. This fragmented pattern of development influences a much larger area of wildlife habitat than that directly impacted.
Therefore, CPW initiated a project in 2008 to develop restoration techniques for big sagebrush habitats impacted by oil and gas development in northwestern Colorado.
Researchers selected the Piceance Basin as the study site for this project. This area is experiencing an unprecedented level of natural gas development. It is also prime habitat for the largest migratory mule deer herd in the United States and other wildlife.
Researchers selected twelve locations in this area to test six different reclamation experiments. Experiments conducted at lower elevations emphasize weed control while the high or middle elevation experiments emphasize plant diversity. All experiments emphasized the establishment of native, perennial plants. Perennial plants provide wildlife nutritious forage for a longer portion of the growing season than do annual plants.
Preliminary results have highlighted the importance of understanding how weed seeds distribute. Factors which increase dispersal of weed seeds (lack of vegetation, disturbed areas with a high edge/area ratio) can hinder restoration, while factors which decrease weed seed dispersal (roughening the soil surface, providing dispersal obstructions) can improve restoration.
The results from this study will help managers choose the most appropriate restoration techniques for big sagebrush habitats impacted by oil and gas development. Restoration efforts will help maintain valuable habitat for Colorado's wildlife.
Associated Publications & Presentations
- Johnston, D. B. (2011). "Movement of weed seeds in reclamation areas." Restoration Ecology 19(4): 446-449.
The presence or absence of obstructions can affect seed dispersal. Reclamation activities often cause changes in the type and amount of such obstructions. The consequences of removing obstructions on the dispersal of undesirable species are unknown. In western North America, reclamation may often proceed in areas surrounded by the invasive Bromus tectorum L. (cheatgrass). The importance of preventing cheatgrass seed dispersal from surrounding landscapes is an unknown factor in reducing cheatgrass competition in these areas. I quantified cheatgrass seed dispersal in the early stages of reclamation, when soils were bare. Four groups of 100 sterilized, fluorescently marked cheatgrass seeds were released in each of three areas in NW Colorado, USA. Seeds were located at night using blacklights four times over 14 days, and the distance between each seed and the point of release was measured. Across sites, dispersal distance averaged 2.4 m, 5% of seeds traveled further than 7.6 m, and maximum recorded distance was 20.8 m. Maximum distances reported in this study are 50-fold higher than previously reported for intact sagebrush ecosystems. I suggest that the difference is due to a lack of impediments to secondary dispersal on bare soil. When reclamation areas are surrounded by weeds such as cheatgrass, seeds dispersing from the perimeter may influence restoration outcome.
Fluorescently-marked cheatgrass seeds dispersing over bare soils.
- Monty, A., Brown, C. S., Johnston, D. B. (2013). "Fire promotes downy brome (B. tectorum) seed dispersal." Biological Invasions 15(5): 1113-1123.
Particularly well-known among the many impacts of the invasive annual grass downy brome (Bromus tectorum, Poaceae) is its ability to alter fire cycles and increase in abundance after fire. However, little is known about how fire influences B. tectorum dispersal. We quantified fire effects on B. tectorum dispersal using three recently burned areas in the western region of the Colorado Rocky Mountains by marking diaspores (seeds) with fluorescent powder, and then recovering them at night using ultraviolet lights. Diaspores were of two types: with and without sterile florets attached. We also characterized vegetation cover and near-surface wind speed in burned and unburned areas. Diaspores travelled much farther in burned areas than in nearby unburned areas (mean ± standard error at the end of the experiment: 209 ± 16 cm and 38 ± 1 cm, respectively; maximal distance at the end of the experiment: 2,274 cm and 150 cm, respectively), indicating an increase in dispersal distance after fire. Diaspores with sterile florets attached dispersed longer distances than those without sterile florets (mean ± standard error at the end of the experiment: 141 ± 14 cm and 88 ± 7 cm, respectively). Vegetation cover was lower and wind speeds were higher in the burned areas. Our results indicate that at least one of the mechanisms by which the spread of B. tectorum is promoted by fire is through increased seed dispersal distance. Preventing movement of seeds from nearby infestations into burned areas may help avoid the rapid population expansion often observed.
- Johnston, D. B. and P. L. Chapman (2014). "Rough surface and high-forb seed mix promote ecological restoration of simulated well pads ." Invasive Plant Science and Management 7: 408-424.
Because of disturbance and exotic plant invasions, ecological restoration is necessary for maintaining functional big sagebrush ecosystems in western North America. Downy brome control is often necessary in restoring this ecosystem type; however, many brome control measures hinder ecological restoration by limiting the types of plants which can be established. Microtopography manipulation may aid weed control by entrapping undesirable seeds. We undertook a field experiment at four sites in the Piceance Basin of western Colorado, USA to test the effects of microtopography (rough with brush mulch or flat with straw mulch), seed mix (high-forb or balanced), and herbicide (140 g ai ha21 imazapic ammonium salt or none) on downy brome control and perennial plant establishment following disturbance. Three years post-treatment, downy brome had become established at two of the four sites, one each with high (GVM) and low (MTN) downy brome seed rain. At GVM, the rough/brush treatment augmented the effectiveness of imazapic, reducing downy brome biomass six-fold. At MTN, the rough/brush surface reduced downy brome biomass 10-fold in the absence of imazapic. Across all four sites, forb and shrub biomass were higher with the high-forb mix, and there was no effect of seed mix on downy brome or annual forb biomass. Restoring a full complement of plant functional groups in big sagebrush ecosystems may be aided by increasing forbs in seed mixes, and manipulating soil microtopography.
- Johnston, D. B. (2015). "Downy brome (Bromus tectorum) control for pipeline restoration." Invasive Plant Science and Management 8(2): 181-192. open access: http://wssajournals.org/doi/pdf/10.1614/IPSM-D-14-00001.1
Energy-extraction disturbances entail soil handling and often have large edge-to-area ratios. These characteristics should be considered when designing weed-control strategies. In western North America, many energy developments coincide with infestations of downy brome, an annual grass that severely curtails productivity, diversity, and habitat value of invaded areas. Downy brome is sensitive to soil compaction and seed burial, both of which may occur when soil is handled. In this study, I examined the effect of soil-density manipulations and herbicide application (105 g ai ha−1 imazapic with 280 g ai ha−1 glyphosate) on six simulated pipeline disturbances in a Wyoming big sagebrush ecosystem invaded by downy brome. Disturbances occurred at the end of the growing season, after ambient downy brome seed rain in the study areas had abated. Treatments and seeding occurred shortly after disturbances. The following spring, downy brome seedling density was 10-fold lower within disturbances than in control areas, but seedling density quickly rebounded in disturbed areas where no herbicide had been applied. In herbicide plots, downy brome seedling density remained low during the first growing season, and shrub cover after 3 yr was eight times higher than in no-herbicide plots. Soil density manipulations via disking and rolling treatments had little effect on downy brome. Prior research has shown that imazapic is more effective when combined with disturbances, such as fire. This study demonstrates that imazapic may also be effective in combination with a disturbance that is timed to bury downy brome seeds.