Chemical control of sand sagebrush: implications for lesser prairie-chicken habitat

Authors: Thacker, Eric; GILLEN, ROBERT - Kansas State University; Gunter, Stacey; Springer, Timothy

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2012
Publication Date: 10/9/2012
Citation: Thacker, E.T., Gillen, R., Gunter, S.A., Springer, T.L. 2012. Chemical control of sand sagebrush: implications for lesser prairie-chicken habitat. Rangeland Ecology and Management. 65(5):516-522.

Interpretive Summary: Habitat loss and degradation have contributed to the decline of lesser prairie-chickens. Herbicides, like 2,4-D, have been used extensively for decades to control sand sagebrush in order to increase forage for livestock. Spraying plant communities with herbicides results in less protective cover for wildlife like lesser-prairie chickens. The objective of our study was to determine if controlling sand sagebrush with 2,4-D would increase dietary resources and what effect it would have on protective cover for lesser prairie-chickens. Recently, treated pastures (< 5 years) had less protective cover without increasing dietary resources (forbs and grasshoppers). Older treatments (> 20 years) still did not provide enough protective cover but had an increase in annual forbs. Removal of sagebrush did not increase perennial forbs, forb species diversity or grasshopper abundance, which are all important dietary resources. Over all, application of 2,4-D reduces protective cover while limiting dietary resources for several years. 2,4-D may have limited use as a habitat management tool because it takes numerous years to reap the benefit of increased annual forb abundance and it may also have a long-term negative impact on habitat for wildlife.

Technical Abstract: Traditional management of rangelands dominated by sand sagebrush (Artemisia filifolia) has emphasized sagebrush control to increase forage for livestock. Since the 1950’s, shrub removal has been primarily achieved with herbicides. Concerns about the declining lesser prairie-chicken (Tympanuchus pallidicinctus) populations have lead to increased scrutiny over the use of herbicides to control shrubs. The objective of our research was to determine changes to lesser prairie-chicken habitat following chemical control of sand sagebrush in Northwest Oklahoma. Pastures ranged in size from 10 to 21 ha. Five pastures were sprayed with 2,4-D in 2003 (RECENT), five were sprayed with 2,4-D in 1984 (OLD), and four received no treatment (SAGE). We measured habitat structure (sagebrush cover, sagebrush density, visual obstruction, and basal grass cover), and dietary-resources (forb density, forb diversity, and grass hopper density) in all pastures from 2003 through 2006. OLD and RECENT pastures had less sagebrush (cover and density) and visual obstruction than SAGE pastures. OLD pastures produced more annual forbs than either SAGE or RECENT pastures. However, SAGE pastures had more perennial forbs than RECENT pastures. Forb species diversity and grasshopper density were unaffected by 2,4-D application. 2,4-D reduced protective cover while providing no increase in forb abundance in RECENT pastures; pastures that had been treated before 1984 (OLD) did have more annual forbs. Our results indicate that it may take several years to realize increases in annual forbs following application of 2,4-D. However, loss of protective cover may persist for multiple years (20+ years). Thus, 2,4-D may have limited use as a habitat management tool because it takes numerous years to reap the benefit of increased forb abundance and it may also have a long-term negative impact on habitat structure.