Effects of Microbiotic Crusts on the Germination and Establishment of Three Range Grasses

Publication Date


Type of Culminating Activity


Degree Title

Master of Science in Interdisciplinary Studies, Plant Soil Ecology



Major Advisor

Marcia Wicklow-Howard


Bromus tectorum L., commonly called cheatgrass, is considered undesirable on rangelands due to its invasive nature and its ability to alter the environment, thereby increasing wildfire frequency (Whisenant, 1990). Land managers consider native perennial bunchgrasses, such as Stipa spp., desirable for the restoration and maintenance of healthy rangelands. Stipa spp. refers to Stipa comata Trin. & Rupr. "needle and thread grass" and Stipa thurberiana Piper "Thurber's needlegrass" throughout the rest of this thesis.

Domestic livestock grazing has changed the plant communities of the Snake River Plain by reducing the density of native perennial grasses and increasing the density of native shrubs and exotic annuals (Miller et al., 1991). Trampling by livestock also reduces the density and biomass of microbiotic crusts (Beymer & Klopatek, 1992;) which are an integral component of ecological communities on the Snake River Plain. Microbiotic crusts are primarily non-vascular plant corrununities which grow on or in the top 1 cm of the soil profile (Brotherson and Rushforth, 1983; Dunne, 1989).

A reduction in the density of native perennial grasses has been correlated with a decrease in microbiotic crust cover (Beymer & Klopatek, 1992). This decrease in microbiotic crusts and native perennial grasses potentially creates an environment suitable for Bromus tectorum establishment.

Consequently, in the past twenty years, there has been increased interest in the role that microbiotic crusts play in ecosystems of semi-arid and arid lands (St. Clair and Johansen, 1993). Are microbiotic crusts important for the recovery of native plant communities?

Thus far, there has been little research into the effects of microbiotic crusts on the germination and establishment of seedlings (Eldridge and Greene, 1994). The present study examines the effects of varying degrees of microbiotic crust cover on the germination and establishment of three range grasses, Bromus tectorum, Stipa thurberiana, and S. comata, as well as the effects of microbiotic crusts on soil moisture and soil nutrients. In addition, germination rates for these three grass species are determined for the southern Snake River Plain.

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