Delaying sheep grazing after wildfire in sagebrush steppe may not affect vegetation recovery

Abstract

Although many land managers prohibit grazing for 2 years after a fire, little research has been conducted to determine the interaction of grazing with vegetation recovery after fire. In a study conducted in sagebrush steppe rangelands after a 2000 wildfire at the United States Sheep Experiment Station in Idaho, the influence of delay and season of sheep grazing on vegetation recovery was measured. A moderate level of sheep grazing was started 1, 2, or 3 years after fire in the autumn or 2 or 3 years after fire in the spring. Pseudoroegneria spicata, the dominant perennial grass, and Crepis acuminata increased in the autumn and non-grazed treatments, whereas perennial forb and Crepis acuminata cover declined in the spring grazing treatments beginning the second year after fire. There was no impact of sheep grazing on cover of Bromus tectorum, an important exotic winter annual grass, probably owing to the lack of autumn germination. In this study, moderate sheep grazing had subtle impacts on vegetation recovery after fire, with spring grazing having more negative consequences. Management decisions on when to start grazing livestock after fire should consider pre-fire ecological conditions, post-fire climatic conditions, and current knowledge of impacts of grazing on plant recovery.