Cattle Grazing as a Biological Control for Broom Snakeweed: Vegetation Response |
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| Authors: | Michael H. Ralphs Jeffery E. Banks |
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| Affiliation: | 1. Rangeland Scientist, US Department of Agriculture–Agricultural Research Service, Poisonous Plant Research Laboratory, Logan, UT, 84341, USA;2. Juab County Agent, Utah State University Cooperative Extension, Nephi, UT 84648, USA;1. Habitat Program Manager, Northern Region Office, Utah Division of Wildlife Resources, Ogden, UT 84405, USA;2. Professor and Research Associate Department of Plant and Wildlife Sciences, Brigham Young University, Provo, UT 84602, USA;3. Research Associate, Department of Plant and Wildlife Sciences, Brigham Young University, Provo, UT 84602, USA;1. Department of Geography, 1922 F St. NW, Washington, DC 20052, United States;2. Department of Earth and Environment, 675 Commonwealth Ave., Boston University, Boston, MA 02215, United States;3. JYM Consulting, 2630 Exposition Blvd., Suite 119B, Austin, TX 78703, United States;4. Centro de Sensoriamento Remoto/UFMG, Av. Antônio Carlos, 6627, Belo Horizonte, MG CEP 31270-900, Brazil;1. Assistant Professor, Department of Wildland Resources, Utah State University, Logan, UT 84322, USA;2. Supervisory Research Ecologist, US Geological Survey, Forest and Rangeland Ecosystem Science Center, Corvallis, OR 97331, USA;3. Assistant Professor, Natural Resource Ecology Laboratory and Department of Ecosystem Science and Sustainability, Colorado State University, in cooperation with the US Geological Survey, Fort Collins Science Center, Fort Collins, CO 80526, USA;4. Research Wildlife Biologist, US Geological Survey Western Ecological Research Center, Dixon, CA 95620, USA;5. Ecologist, US Geological Survey, Fort Collins Science Center, Fort Collins, CO 80526, USA;6. Environmental Scientist, California Department of Fish and Wildlife, Napa, CA 94558, USA. |
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| Abstract: | Broom snakeweed (Gutierrezia sarothrae [Pursh] Britton & Rusby) increases and dominates rangelands following disturbances, such as overgrazing, fire, and drought. However, if cattle can be forced to graze broom snakeweed, they may be used as a biological tool to control it. Cattle grazed broom snakeweed in May and August 2004–2007. Narrow grazing lanes were fenced to restrict availability of herbaceous forage to force cattle to graze broom snakeweed. They used 50–85% of broom snakeweed biomass. Mature broom snakeweed plant density declined because of prolonged drought, but the decline was greater in grazed lanes. At the end of the study, density of mature plants in grazed lanes was 0.31 plants · m-2, compared with 0.79 plants · m-2 in ungrazed pastures. Spring precipitation in 2005 was 65% above average, and a new crop of seedlings established following the spring grazing trial. Seedling establishment was greater in the spring-grazed lanes in which the soil had been recently disturbed, compared with the ungrazed transects and summer-grazed lanes. The cattle were not able to use the large volume of new broom snakeweed plants in the spring-grazed pasture. They did reduce the number of seedlings and juvenile plants in the summer-grazed pasture. Intense grazing pressure and heavy use did not adversely affect crested wheatgrass (Agropyron cristatum [L.] Gaertn.) cover, and it was actually higher in the summer grazed lanes than the ungrazed control transects. In moderate stands of broom snakeweed, cattle can be forced to graze broom snakeweed and reduce its density without adversely affecting the associated crested wheatgrass stand. |
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