Effect of burn season and grazing deferment on mountain big sagebrush plant communities

Authors: Wilmer, Hailey; McGranahan, Devan; Moffet, Corey; Taylor, Joshua - Bret

Submitted to: Plant Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2023
Publication Date: 5/2/2023
Citation: Wilmer, H.N., McGranahan, D.A., Moffet, C., Taylor, J.B. 2023. Effect of burn season and grazing deferment on mountain big sagebrush plant communities. Plant Ecology. 224:501-512. https://doi.org/10.1007/s11258-023-01317-1.
DOI: https://doi.org/10.1007/s11258-023-01317-1

Interpretive Summary: Rangeland managers have several vegetation management goals in shrub ecosystems. Prescribed fire can be one tool to manage for these goals but post-fire grazing is commonly restricted to ensure plant community recovery. We report the results of a four-year replicated study comparing the effects of season of fire (spring or fall) and sheep grazing deferment on plant communities in a mountain big sagebrush-bunchgrass ecosystem at the US Sheep Experiment Station in Idaho, USA. After four years, fall and spring burned areas had increased perennial native grass cover. The effects and interactions among fire and grazing management tools is context-dependent across climatic gradients in the sagebrush biome. At our study site, prescribed fire seasonality and grazing deferment have important economic but relatively moderate ecological implications.

Technical Abstract: Rangeland managers have a limited toolbox to reach vegetation management goals in shrub ecosystems. Prescribed fire can be used to improve habitat and forage quality, but it is commonly assumed that deferring grazing after a fire is necessary to ensure plant community recovery. We report the results of a four-year replicated study simultaneously comparing the effects of season of fire (spring or fall) and sheep grazing deferment (either no grazing for one or two growing seasons after fire, or no deferment, in which domestic sheep returned in the subsequent fall season after fire) on plant communities in a mountain big sagebrush-bunchgrass ecosystem at the US Sheep Experiment Station on the Snake River Plain of Idaho, USA. Burn treatment had a consistent effect on plant community composition, whereas we found no evidence that grazing deferment for either one or two seasons affected plant community composition in any plots compared to no grazing deferment. However, deferred areas did have more litter relative to grazed areas four years after the fire. One year after fire, fall and spring burned plots had more native forb cover and reductions in perennial native shrubs. Both burned areas had more bare ground than unburned areas. After four years, fall and spring burned areas had increased perennial native grass cover. The effects and interactions among fire and grazing management tools is context-dependent across climatic gradients in the sagebrush biome. At our study site, prescribed fire seasonality and grazing deferment have important economic but relatively moderate ecological implications.