Submitted to: Agricultural Research Service Publication
Publication Type: Other
Publication Acceptance Date: January 10, 2004
Publication Date: June 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. Agricultural Research Service Publication. 61 p. Interpretive Summary: This progress 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 results and comments made in the report are still preliminary, as data analysis and projects are still ongoing. The purpose of the 'Wyoming Big Sagebrush Program' is to provide a better understanding of the ecology and management of this sagebrush alliance. The ecology focus is directed towards: (1) determining the biological potentials of the alliance and how these potentials impact interpretation of habitat guidelines, (2) develop a classification system of plant associations within the alliance, (3) determine the effects of environmental characteristics influencing development of plant associations, (4) determine the short and long-term effects of wild and prescribed fire to plants and invertebrates, and (5) determine effects of long-term climate variability to productivity, plant composition, and vegetation dynamics. The management effort involves development of guidelines and management alternatives in the Wyoming big sagebrush alliance focusing on fire and livestock grazing. We are attempting to develop a risk assessment of community susceptibility to cheatgrass or other weed invasion after fire disturbance and to develop grazing guidelines following fire in the sagebrush steppe. Defining community susceptibility to fire will assist in development of appropriate management actions and assist in predicting outcomes of fire in the Wyoming big sagebrush alliance.
Technical Abstract: The Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh) alliance is the most extensive of the big sagebrush complex in the Intermountain West (Miller and Eddleman 2000, Tisdale 1994). This alliance provides critical habitat for many sagebrush obligate and facultative wildlife species as well as a forage base for livestock production. Lack of information on the vegetation potential of the Wyoming big sagebrush alliance and inconsistent vegetation sampling techniques have resulted in disagreement over management guidelines and habitat needs of sagebrush obligates. Our goal was to provide information regarding the structure and cover potentials of the Wyoming big sagebrush alliance in eastern Oregon to assist land managers. Our objectives were to; 1) describe vegetation characteristics in relatively undisturbed Wyoming big sagebrush plant communities; 2) develop a classification system of plant communities for the Wyoming big sagebrush alliance; and 3) compare stand level vegetation characteristics with greater sage grouse habitat guidelines developed by the Bureau of Land Management et al. (2000) and Connelly et al. (2000). We intensively sampled 107 relatively, undisturbed high ecological condition sites across three ecological provinces (High Desert, Humboldt, and western Snake River) in eastern Oregon and northern Nevada in 2001 and 2002. Using multivariate analysis, differences species composition and functional group cover values indicated grouping Wyoming big sagebrush communities into associations by dominant perennial bunchgrass species was appropriate. Five Wyoming big sagebrush associations were identified: bluebunch wheatgrass (Agropyron spicatum (Pursh) Scribn. & Smith), Thurber's needlegrass (Stipa thurberiana Piper), needle-and-thread (Stipa comata Trin. & Rupr.), Idaho fescue (Festuca idahoensis Elmer), and bluebunch wheatgrass/Thurber's needlegrass. Using a strict interpretation of the Bureau of Land Management et al. (2000) habitat guidelines, 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 by Connelly et al. (2000) for breeding and brood-rearing habitats in arid sagebrush communities were met by 18% and 63% of the sites, respectively. The winter habitat requirements were identical for both guidelines and were met on 70% of the sites. Individual associations within the Wyoming big sagebrush alliance also varied in their vegetation cover. The underlying problem with current guidelines is a scale issue. When guidelines are interpreted, they imply stand or landscape scale, but they were largely developed from smaller scale information. Guidelines also did not differentiate between sagebrush species or subspecies. 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 in eastern Oregon. Guidelines also need to recognize that different sagebrush alliances and associations have varying vegetation cover potentials.