The Influence of Disturbance Events and Rehabilitation on Sagebrush Steppe Ecosystems

Publication Date


Type of Culminating Activity


Degree Title

Master of Science in Biology



Major Advisor

Stephen Novak


Disturbance events such as grazing and wildfire are common events in sagebrush steppe ecosystems in the intermountain west. A variety of models have been developed to explain the composition of vegetation as a result of these disturbances. The state and transition model, first introduced in 1989, is the currently accepted model and incorporates non-equilibrium theory to explain the collection of species in communities. However, the descriptions of the states are qualitative and not practical for use in determining the state of a community based on sampling data. Quantitative values for shrubs, perennial forbs, grasses and annuals were developed for each state in the state and transition model using prior studies from the literature. The composition of the vegetation following four fires in sagebrush steppe communities was analyzed using the quantified values for the four plant forms. The relative canopy coverage differed by aspect, burn history and rehabilitation efforts. North-facing slopes experiencing moderate intensity fires can recover without rehabilitation. Re-seeding or replanting activities on north-facing slopes may provide conditions for the invasion by non-native annuals and are therefore counterproductive. South-facing slopes have warmer and drier conditions and require rehabilitation efforts to avoid mono cultures of invasive annuals following wildfire. Greenhouse germination of soil samples from the fire sites provided an analysis of the similarity of seedbanks to field vegetation and among different treatments. Seed banks are comprised mainly of annual species regardless of vegetation present, fire history, aspect or rehabilitation history. The seedbank therefore represents a potential source for reduced biodiversity within sagebrush steppe ecosystems.

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