Disturbance caused by mining requires reclamation to return the area to a desirable state. Managers must think about a variety of issues including weed management and desirable species establishment. Herbicides are commonly used to control weeds that would compete with seeded species if left uncontrolled. Because common weed species on reclamation sites are often broadleaf annuals, herbicides are typically broadleaf specific. Reclamation seed mixes are often composed of grass, forb and shrub species. However, forb and shrub establishment may become challenging when broadleaf herbicides are used. Unintended impacts of herbicides on desirable species may inhibit the progress of reclamation. Our objective was to evaluate direct impacts of herbicides on 12 desirable species and two weed species common in reclamation. In a greenhouse experiment we applied 10 herbicide treatments at three timings (pre-emergence and two post-emergent timings) in a factorial arrangement set in a randomized complete block design. Species included 10 desirable grasses, two desirable forbs, and two broadleaf weeds. We recorded damage ratings weekly and harvested aboveground biomass from all plants 30 days after the final herbicide application. The response of different species was affected by timing of herbicide application, where pre-emergence treatments resulted in the lowest biomass (p<0.0001). Herbicide effects varied by herbicide application timing similarly across all species (p<0.0001). Various species were also impacted by the herbicides differently, across all timings (p<0.0001). Herbicides causing the least damage included saflufenacil and aminocychlopyrachlor+chlorsulfuron at a low rate, particularly with crested wheatgrass and streambank wheatgrass. Species most negatively affected by herbicides (including aminocychlopyrachlor+chlorsulfuron at a high rate and imazapic) were blue flax, alkali sacaton, and the weed species. Understanding potential herbicide impacts on seeded species may illuminate some problems facing reclamation projects.
Oral presentation and poster titles, abstracts, and authors from the Society for Range Management (SRM) Annual Meetings and Tradeshows, from 2013 forward.