Influence Of Fall Grazing By Sheep On Plant Productivity, Shrub Age Class Structure And Herbaceous Species Diversity In Sagebrush Steppe

Managing Wyoming Big Sagebrush (Artemisia tridentata ssp. wyomingensis) systems biologically with grazing can potentially reduce costs and increase both biodiversity and understory production as well as rejuvenate Wyoming Big Sagebrush (ARTRWY). Sheep were provided a protein-energy supplement to facilitate use of the secondary metabolites found in ARTRWY forage. Phytomass ( ) was estimated for the following plant categories: total phytomass, current annual growth (CAG) of ARTRWY, the woody portion of ARTRWY, CAG of other shrubs, the woody portion of other shrubs, grasses, forbs, litter, and standing dead material. I also measured plant species richness and abundance, as well as estimates of the age class structure of sagebrush. One year following grazing, total phytomass decreased by 43%, due primarily to the reduction of ARTRWY. The CAG of ARTRWY decreased by 66%, while grasses increased by 43%, forbs increased 60%, and the number of species encountered in the grazed plots increased 42%.