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Effects of Supplemented Fall Sheep Grazing on a Plant Community Dominated by Wyoming Big Sagebrush
Ryan D. Woodland, Idaho Department of Lands, Idaho Falls, ID, Neil E. West and Frederick D. Provenza, Utah State University, Logan, UT
Traditional chemical and mechanical treatments of Wyoming Big Sagebrush (Artemisia tridentata ssp. wyomingensis) are costly and have typically focused on increasing forage for livestock production. Managing these systems biologically with grazing can potentially reduce costs and increase both biodiversity and understory production as well as rejuvenate Wyoming Big Sagebrush (ARTRWY). This experiment occurred on Deseret Land & Livestock in northern Utah in October 2003. We used 120 dry ewes to graze 3, 60 m X 40 m plots (40 sheep/plot). Sheep were provided a protein-energy supplement to offset the negative effects of the terpenes found in ARTRWY. We used the reference unit method, to estimate ( ) the following categories immediately before, immediately after, and one year following grazing: total phytomass, CAG of ARTRWY, woody portion of ARTRWY, CAG of other shrubs, woody portion of other shrubs, grasses, forbs, litter (woody and herbaceous), and standing dead (woody and herbaceous). Plant species richness and abundance as well as estimates of the age class structure of sagebrush were also measured. Sheep used 98% of the total available forage. One year following grazing, in the grazed plots, total phytomass decreased by 48%, CAG of ARTRWY decreased by 66% while grasses increased by 43% and forbs increased by 60%. One year following grazing, the number of species encountered in the grazed plots had increased by 42%. Considering the short time frame of our ongoing measurements, it is less clear what effect grazing will have on the age class structure of ARTRWY.
Email: rwoodland@idl.idaho.gov