Title: Postfire shrub-cover dynamics: a 70-year fire history in big sagebrush communities. Authors
Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: June 1, 2010
Publication Date: March 15, 2011
Citation: Moffet, C.A., Taylor, J.B., Booth, D.T. Postfire shrub-cover dynamics: a 70-year fire history in big sagebrush communities. IX International Rangeland Congress Proceeding. Rosario, Argentina. April 2 - 8, 2011. Interpretive Summary: The effect of burning in sagebrush steppe has important implications for livestock production and wildlife habitat. In order to design burn rotation plans to meet livestock production and wildlife habitat objectives, an understanding of the fire-effect duration and the postfire response of shrubs is needed. We used aerial photography to sample sagebrush, bitterbrush, and horsebrush cover in mountain big sagebrush communities at the USDA, ARS, U.S. Sheep Experiment Station near Dubois, ID, with 70 years of fire history to determine when cover of the shrub species return to preburn cover. The results from this study demonstrate that in mountain big sagebrush communities, sagebrush and horsebrush returned to preburn cover by 18 years and bitterbrush returned to preburn cover by 6 years after fire. This information will allow land managers to design burn plans that will enhance livestock production and maintain preferred nesting habitat for sage grouse.
Technical Abstract: Land managers use prescribed fire to meet rangeland management objectives. This study was conducted to quantify, from present conditions, the effect of time since last burn (TSLB) on shrub cover over 70 yr of fire history. We sampled mountain big sagebrush communities at the USDA, ARS, U.S. Sheep Experiment Station with very-large-scale-aerial (VLSA) imagery and measured sagebrush, antelope bitterbrush (Purshia tridentata [Pursh] DC.), and spineless horsebrush (Tetradymia canescens DC.) cover. Segmented regression was used to describe distinct cover phases. Phase 1 represented when shrub cover responded to TSLB and Phase 2 represented when shrub cover did not respond to TSLB and, thus, had reached steady state. In Phase 1, total shrub, sagebrush, and bitterbrush cover increased with TSLB. Bitterbrush cover reached Phase 2 in approximately 1/3 the time (5.7 yr) that it took for sagebrush (18.3 yr), horsebrush (17.7 yr), and total shrub cover (17.6 yr). Horsebrush had 2 responses with respect to TSLB in Phase 1. In the first 8.7 yr TSLB, cover increased from 0.4 to 2.9% and, in the next 9.0 yr TSLB, cover diminished to 0.2%. Steady-state cover for sagebrush, bitterbrush, horsebrush, and total shrub was 30, 3, 0.2, and 40%, respectively. In the absence of fire (>70 yr TSLB), shrub cover exceeded an ideal value from a livestock production and wildlife habitat perspective. These data described postfire recovery rates of shrubs in mountain big sagebrush communities that can be used to facilitate managers in designing rangeland management objectives to meet livestock and wildlife management goals.