Anchoring the sagebrush sea: Thresholds for recovery of Wyoming big sagebrush communitites. Salo, Lucinda^*,1, Unnasch, Robert², Pyke, David³, ¹ USGS Forest & Rangeland Ecosystem Science Ctr., Boise, ID² The Nature Conservancy, Boise, ID³ USGS Forest & Rangeland Ecosystem Science Ctr., Corvallis, OR

ABSTRACT- Waves of change have transformed the sagebrush regions of the Intermountain West since Europeans first arrived. Invasion by cheatgrass (Bromus tectorum) has increased the frequency and extent of wildfires which, in turn, has resulted in the loss of millions of hectares of big sagebrush (Artemisia tridentata). This threatens sagebrush obligate species such as sage grouse (Centrocercus urophasianus), and several raptor species through its effect on their prey base. Wyoming big sagebrush (A. tridentata ssp. wyomingensis) occurs on the driest big sagebrush sites, making them the least resistant to, and least resilient after, disturbances such as fire. Identifying and describing the biophysical thresholds between recovery of native Wyoming big sagebrush communities and conversion to cheatgrass monocultures following fire will aid us in maintaining these ecosystems and in focusing expensive and difficult restoration efforts to sites at greatest risk of conversion to exotics. This work is tapping local experts' knowledge as well as characterizing vegetation and soils on Wyoming big sagebrush sites a range of years after wildfire in the northern Great Basin. Incorporating vegetation, soils, climatic, and management data into state and transition models, we are predicting successional patterns and thresholds for recovery of these communities after fire. Both local experts' knowledge and field data indicate that the amount of live below-ground plant material is a critical factor in determining the ability of these systems to recover after fire. This includes root reserves of perennial grasses and of resprouting shrubs.

KEY WORDS: artemisia tridentata, cheatgrass, fire ecology, state and transition models