Fire and Restoration of Sagebrush Ecosystems

Abstract

Wildlife managers often resort to prescribed fire to restore sagebrush (Artemisia spp.) ecosystems thought to have been affected by fire exclusion. However, a fire mosaic of burned and unburned areas may be tolerated by certain wildlife but can be detrimental to sagebrush obligates. This article assesses evidence about the historical frequency and pattern of fire in sagebrush ecosystems and the need for prescribed fire. Fire-scar data from nearby forests require adjustment to estimate fire rotation, the time required to burn once through a sagebrush landscape. Estimates from forests require correction for unburned area and because sagebrush burns less often than forests. Recovery time also might indicate fire rotation. Mountain big sagebrush (Artemisia tridentata ssp. vaseyana) recovers within about 35–100 or more years after fire, and Wyoming big sagebrush (A. t. ssp. wyomingensis) requires 50–120 or more years. Fire rotation in other ecosystems is 2 or more times the recovery period. Together, the evidence suggests fire rotations may be a minimum of 325–450 years in low sagebrush (A. arbuscula), 100–240 years in Wyoming big sagebrush, 70–200 years or more in mountain big sagebrush, and 35–100 years in mountain grasslands with a little sagebrush. Given these long rotations, fire exclusion likely has had little effect in most sagebrush areas. If maintaining and restoring habitat for sagebrush-dependent species is the goal, fire should be suppressed where there is a threat of cheatgrass (Bromus tectorum). Elsewhere, fire does not need to be reintroduced until native understory plants can be restored, so that sagebrush ecosystems can fully recover from fire.