Sheep bedding in the Centennial Mountains of Montana and Idaho: effects on vegetation

Authors: Seefeldt, Steven; Leytem, April

Submitted to: Western North American Naturalist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2011
Publication Date: 12/20/2011
Citation: Seefeldt, S.S., Leytem, A.B. 2011. Sheep bedding in the Centennial Mountains of Montana and Idaho: effects on vegetation. Western North American Naturalist. 71(3):361-373.

Interpretive Summary: During the summer in the western United States, many bands of sheep are grazed in the mountains. At night a sheep band is usually herded together to protect them from theft and predation. Typically this bedding occurs on the same places for years. The purpose of this paper was to determine the impact of this sheep bedding on the vegetation in the bedded areas compared to outside the bedding areas. The study was conducted on sheep bedding areas in the summer range of the U. S. Sheep Experiment Station, which is located in the Centennial mountains on the Idaho and Montana border. Inside the bedding area there was always less plant weight and plant cover compared to outside the bedding area immediately after bedding and 1 and 2 years after bedding. However, when attention is paid to the types of vegetation, inside the bedding areas there is a very large increase in annual forb cover compared to outside the bedding areas. Several of these forb species that increase are the same species as are found the year after a fire in the sagebrush steppe. There was no evidence that sheep bedding areas were susceptible to invasion of nonnative plant species. Plant recovery after bedding inside the bedding areas was rapid and predictable. These bedding areas, which are utilized by sheep for one or two days a year for two out of three years, appear to be quite stable in plant succession after sheep bedding.

Technical Abstract: During summer months in western North America many bands of sheep are grazed in the mountains. At night a sheep band is concentrated in, often historic, bedding areas to guard them from theft and predation. We analyzed the impacts of sheep bedding on the vegetation in bedding areas compared to vegetation outside these areas. Perennial forb and shrub cover were greater outside of bedding areas than inside bedding areas. Perennial grass cover was only greater the year after sheep bedding outside the bedding areas compared to inside. Annual forb cover, however, was greater inside bedding areas one and two years after sheep grazing compared to outside. Annual forb cover increased an order of magnitude inside the bedding areas the year after bedding and then declined the following year. Total forb cover was greater outside the bedding areas immediately after sheep bedding, whereas perennial cover was only greater outside the bedding areas one and two years after sheep bedding compared to inside. Forb and grass biomass were greater outside the bedding areas compared to inside the bedding area. Total vegetation biomass outside the bedding areas was more than double the amount inside the bedding areas immediately after bedding. In the year after bedding, vegetation biomass inside the bedding areas increased, but was still less than outside the bedding areas. In the second year after bedding, overall vegetation biomass inside and outside the bedding areas was reduced compared to the first year after bedding, and there was more vegetation biomass outside the bedding areas compared to inside. The number of annual forb species increased the year after grazing and decreased the following year. Importantly, there was no evidence that sheep bedding areas were susceptible to invasion of nonnative plant species. These bedding areas, which are only utilized by sheep for one or two days a year for two out of three years, appear to be quite resilient and recover quickly after sheep bedding.