ECOLOGY OF THE WYOMING BIG SAGEBRUSH ALLIANCE IN THE NORTHERN GREAT BASIN: 2004 PROGRESS REPORT

Authors: Bates, Jonathan - Jon; Davies, Kirk; MILLER, RICK - OREGON STATE UNIV

Submitted to: Eastern Oregon Agricultural Research Center
Publication Type: Experiment Station
Publication Acceptance Date: 2/1/2004
Publication Date: 5/1/2004
Citation: Bates, J.D., Davies, K., Miller, R. 2004. Ecology of the wyoming big sagebrush alliance in the northern great basin: 2004 progress report. Eastern Oregon Agricultural Research Center. 61 p.

Interpretive Summary: This report presents a summary of research findings in the Wyoming big sagebrush alliance of eastern Oregon and northern Nevada. The report includes results from the 2001, 2002, and 2003 field seasons. The purpose of the 'Wyoming Big Sagebrush Program' is to provide a better understanding of the ecology and management of this sagebrush alliance. The Wyoming big sagebrush alliance is the most extensive of the big sagebrush complex in the Intermountain West and provides habitat for many wildlife species as well as a forage for livestock production. Our study objectives have been to; 1) describe vegetation characteristics in relatively undisturbed Wyoming big sagebrush plant communities; 2) determine if distinct plant associations could be defined; 3) compare stand level vegetation characteristics with current greater sage grouse habitat guidelines; and 4) evaluate response of these communities to wild fire. In our studies, five Wyoming big sagebrush associations were identified; bluebunch wheatgrass, Thurber's needlegrass, needle-and-thread, Idaho fescue, and bluebunch wheatgrass/Thurber's needlegrass. Habitat guidelines developed for mesic communities for breeding birds were not met by any sites sampled. Guidelines developed for arid communities for breeding and brood-rearing habitats in arid sagebrush communities were met by 18% and 63% of the sites, respectively. The results suggest that local expert judgment be used to develop guidelines in the sagebrush ecosystem. Vegetation cover guidelines for wildlife habitat could be improved by incorporating our survey of the Wyoming big sagebrush alliance. First and second year post-wildfire vegetation recovery in the Wyoming big sagebrush alliance was assessed in the Sheepshead Mountains in southeastern Oregon. Plant communities affected by the wildfire were Wyoming big sagebrush/bluebunch wheatgrass, and Wyoming big sagebrush/Thurber's needlegrass associations. This was an intense wildfire, characterized by the elimination of sagebrush, increased bareground, and decreased cover of herbaceous vegetation. The Thurber's needlegrass association was the most severely impacted by the wildfire. Perennial grasses experienced high mortality. Understory response to the fire in the bluebunch wheatgrass association varied depending on site. Recovery of perennial grasses in this association has been more rapid compared their recovery in the Thurber's needlegrass association. The high mortality of perennial grasses and presence of cheatgrass in the Thurber's needlegrass association indicates that there is a risk for annual grass replacement of this sagebrush steppe association after wildfire. Because bluebunch wheatgrass and Thurber's needlegrass associations are often found in close proximity efforts should be made to limit wildfire in these plant associations.

Technical Abstract: The Wyoming big sagebrush alliance is the most extensive of the big sagebrush complex in the Intermountain West. This alliance provides critical habitat for many sagebrush obligate and facultative wildlife species as well as a forage base for livestock production. Limited information on vegetation structure, composition, and spatial heterogeneity has resulted in disagreement over describing the vegetation potential for meeting management goals across the Wyoming big sagebrush alliance. Our study objectives were to; 1) describe vegetation characteristics in relatively undisturbed Wyoming big sagebrush plant communities; 2) determine if distinct plant associations could be defined; 3) compare stand level vegetation characteristics with current greater sage grouse habitat guidelines; and 4) evaluate response of these communities to wild fire. We intensively sampled 107 relatively, undisturbed high ecological condition sites across four ecological provinces in eastern Oregon and northern Nevada in 2001 and 2002. Multivariate analysis indicated that grouping Wyoming big sagebrush communities into associations by dominant perennial bunchgrass species was appropriate. Five Wyoming big sagebrush associations were identified; bluebunch wheatgrass, Thurber's needlegrass, needle-and-thread, Idaho fescue, and bluebunch wheatgrass/Thurber's needlegrass. Using a strict interpretation oft habitat guidelines for mesic communities, none of the high ecological condition sites met sage grouse nesting or brood-rearing habitat requirements and only 30% met the sub-optimum brood-rearing habitat requirements. Guidelines developed for arid communities for breeding and brood-rearing habitats in arid sagebrush communities were met by 18% and 63% of the sites, respectively. These results strongly suggest that local expert judgment be used due to the variability across the sagebrush biome. When guidelines are interpreted, they imply stand or landscape scale, but they were largely developed from smaller scale information. Management is applied at stand or landscape levels, therefore information is required that reflects these scales. Vegetation cover guidelines for wildlife habitat could be improved by incorporating our survey of the Wyoming big sagebrush alliance across the northwestern portion of the sagebrush biome. First and second year post-wildfire vegetation recovery in the Wyoming big sagebrush alliance was assessed in the Sheepshead Mountains in southeastern Oregon. A wildfire burned over 16,000 ha across the northern portion of the Sheepshead range in August 2001. Prior to the fire, plots had been established and measured in the area in June 2001. Plots were sampled in 2002 and 2003 to assess early successional response to severe wildfire conditions. Plant communities affected by the wildfire were represented by Wyoming big sagebrush/bluebunch wheatgrass, and Wyoming big sagebrush/Thurber's needlegrass associations. The Sheepshead burn was an intense wildfire, characterized by the elimination of sagebrush on all study plots increased bareground, and cover of herbaceous vegetation, litter, moss, and crust declined significantly. The Wyoming big sagebrush/Thurber's needlegrass association was the most severely impacted by the wildfire. Perennial grass cover and density were significantly reduced by the wildfire. Cheatgrass has increased slowly in cover but because of the reduction in the perennial grass component much of the area in this association remains open to further annual grass colonization. Understory response to the fire in the Wyoming big sagebrush/bluebunch wheatgrass association varied depending on site. Recovery of perennial grasses in this association has been more rapid when compared to perennial grass recovery in the Wyoming big sagebrush/Thurber's needlegrass association. Bluebunch wheatgrass was less affect